[PATCH v8 0/9] PCI: endpoint: pci-ep-msi: Add embedded doorbell fallback

[PATCH v8 0/9] PCI: endpoint: pci-ep-msi: Add embedded doorbell fallback

[Koichiro Den]

Hi,

Some endpoint platforms cannot use a GIC ITS-backed MSI domain for
EP-side doorbells. In those cases, endpoint function (EPF) drivers
cannot provide a doorbell to the root complex (RC), and features such as
vNTB may fall back to polling with significantly higher latency.

This series adds an alternate doorbell backend based on the DesignWare
PCIe controller's integrated eDMA interrupt-emulation feature. The RC
rings the doorbell by doing a single 32-bit MMIO write to an eDMA
doorbell location exposed in a BAR window. The EP side receives a Linux
IRQ that EPF drivers can use as a doorbell interrupt, without relying on
MSI message writes reaching the ITS.

To support this, the series:

  - Adds an EPC auxiliary resource query API so EPF drivers can discover
    controller-integrated resources (DMA MMIO, doorbell MMIO, and DMA LL
    memory).
  - Updates DesignWare EP controllers to report integrated eDMA
    resources via the new API.
  - Updates dw-edma to provide a dedicated virtual IRQ for interrupt
    emulation and to perform the core-specific deassert sequence.
  - Describes an RK3588 BAR4 reserved subregion so EPF drivers can reuse
    a platform-owned fixed BAR mapping for the doorbell target.
  - Updates pci-epf-test and pci-epf-vntb to reuse a pre-exposed
    BAR/offset and to honor per-doorbell IRQ flags.


Dependencies
------------

The following two split-out series are prerequisite for this series:

  (1). [PATCH v2 0/4] PCI: endpoint: Doorbell-related fixes
       https://lore.kernel.org/linux-pci/20260217063856.3759713-1-den@valinux.co.jp/
  (2). [PATCH 0/2] dmaengine: dw-edma: Interrupt-emulation doorbell support
       https://lore.kernel.org/dmaengine/20260215152216.3393561-1-den@valinux.co.jp/


Tested on
---------

I re-tested the v8 embedded (DMA) doorbell fallback path (via pci-epf-test)
on R-Car Spider boards:

  $ ./pci_endpoint_test -t DOORBELL_TEST
  TAP version 13
  1..1
  # Starting 1 tests from 1 test cases.
  #  RUN           pcie_ep_doorbell.DOORBELL_TEST ...
  #            OK  pcie_ep_doorbell.DOORBELL_TEST
  ok 1 pcie_ep_doorbell.DOORBELL_TEST
  # PASSED: 1 / 1 tests passed.
  # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0

with the following message observed on the EP side:

  [   51.332944] pci_epf_vntb pci_epf_vntb.0: Can't find MSI domain for EPC
  [   51.333507] pci_epf_vntb pci_epf_vntb.0: Using embedded (DMA) doorbell fallback

(Note: for the test to pass on R-Car Spider, one of the following was required:
 - echo 1048576 > functions/pci_epf_test/func1/pci_epf_test.0/bar2_size
 - apply https://lore.kernel.org/linux-pci/20260210160315.2272930-1-den@valinux.co.jp/)


Performance test: vNTB ping latency
-----------------------------------

Setup:
  - configfs (R-Car Spider in EP mode):

      cd /sys/kernel/config/pci_ep/
      mkdir functions/pci_epf_vntb/func1
      echo 0x1912 >   functions/pci_epf_vntb/func1/vendorid
      echo 0x0030 >   functions/pci_epf_vntb/func1/deviceid
      echo 32 >       functions/pci_epf_vntb/func1/msi_interrupts
      echo 4 >        functions/pci_epf_vntb/func1/pci_epf_vntb.0/db_count
      echo 128 >      functions/pci_epf_vntb/func1/pci_epf_vntb.0/spad_count
      echo 1 >        functions/pci_epf_vntb/func1/pci_epf_vntb.0/num_mws
      echo 0x100000 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw1
      echo 0x1912 >   functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_vid
      echo 0x0030 >   functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_pid
      echo 0x10 >     functions/pci_epf_vntb/func1/pci_epf_vntb.0/vbus_number
      echo 0 >        functions/pci_epf_vntb/func1/pci_epf_vntb.0/ctrl_bar
      echo 4 >        functions/pci_epf_vntb/func1/pci_epf_vntb.0/db_bar [*]
      echo 2 >        functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw1_bar
      ln -s controllers/e65d0000.pcie-ep functions/pci_epf_vntb/func1/primary/
      echo 1 > controllers/e65d0000.pcie-ep/start

      [*]: On R-Car Spider, a hack is currently needed to use BAR4 for
	   the doorbell. I'll consider posting a patch for that
	   separately.

  - ensure ntb_transport/ntb_netdev are loaded on both sides

Results:

  - Without this series (pci.git main)

    $ ping -c 10 10.0.0.11
    PING 10.0.0.11 (10.0.0.11) 56(84) bytes of data.
    64 bytes from 10.0.0.11: icmp_seq=1 ttl=64 time=6.04 ms
    64 bytes from 10.0.0.11: icmp_seq=2 ttl=64 time=12.6 ms
    64 bytes from 10.0.0.11: icmp_seq=3 ttl=64 time=7.40 ms
    64 bytes from 10.0.0.11: icmp_seq=4 ttl=64 time=5.38 ms
    64 bytes from 10.0.0.11: icmp_seq=5 ttl=64 time=11.4 ms
    64 bytes from 10.0.0.11: icmp_seq=6 ttl=64 time=9.42 ms
    64 bytes from 10.0.0.11: icmp_seq=7 ttl=64 time=3.36 ms
    64 bytes from 10.0.0.11: icmp_seq=8 ttl=64 time=9.48 ms
    64 bytes from 10.0.0.11: icmp_seq=9 ttl=64 time=4.24 ms
    64 bytes from 10.0.0.11: icmp_seq=10 ttl=64 time=10.4 ms

  - With this series (on top of pci.git main + Dependency (1) and (2))

    $ ping -c 10 10.0.0.11
    PING 10.0.0.11 (10.0.0.11) 56(84) bytes of data.
    64 bytes from 10.0.0.11: icmp_seq=1 ttl=64 time=0.935 ms
    64 bytes from 10.0.0.11: icmp_seq=2 ttl=64 time=0.805 ms
    64 bytes from 10.0.0.11: icmp_seq=3 ttl=64 time=0.833 ms
    64 bytes from 10.0.0.11: icmp_seq=4 ttl=64 time=0.886 ms
    64 bytes from 10.0.0.11: icmp_seq=5 ttl=64 time=0.861 ms
    64 bytes from 10.0.0.11: icmp_seq=6 ttl=64 time=0.929 ms
    64 bytes from 10.0.0.11: icmp_seq=7 ttl=64 time=0.970 ms
    64 bytes from 10.0.0.11: icmp_seq=8 ttl=64 time=0.946 ms
    64 bytes from 10.0.0.11: icmp_seq=9 ttl=64 time=0.975 ms
    64 bytes from 10.0.0.11: icmp_seq=10 ttl=64 time=0.881 ms

---

Changelog
---------

* v7->v8 changes:
  - Deduplicate request_irq()/free_irq() calls based on virq (shared
    IRQ) rather than doorbell type, as suggested during review of v7
    Patch #7.
  - Clean up the pci_epf_alloc_doorbell() error path, as suggested
    during review of v7 Patch #9.
  - Use range_end_overflows_t() instead of an open-coded overflow check,
    following discussion during review of v7 Patch #5.
  - Add a write-data field to the DOORBELL_MMIO aux-resource metadata
    and plumb it through to the embedded doorbell backend (DesignWare
    uses data=0).

* v6->v7 changes:
  - Split out preparatory patches to keep the series below 10 patches.
  - Add support for platforms where the eDMA register block is fixed
    within a reserved BAR window (e.g. RK3588 BAR4) and must be reused
    as-is.
  - Introduce a dedicated virtual IRQ and irq_chip (using
    handle_level_irq) for interrupt-emulation doorbells instead of
    reusing per-channel IRQs. This avoids delivery via different IRQs on
    platforms with chip->nr_irqs > 1.

* v5->v6 changes:
  - Fix a double-free in v5 Patch 8/8 caused by mixing __free(kfree) with
    an explicit kfree(). This is a functional bug (detectable by KASAN),
    hence the respin solely for this fix. Sorry for the noise. No other
    changes.

* v4->v5 changes:
  - Change the series subject now that the series has evolved into a
    consumer-driven set focused on the embedded doorbell fallback and its
    in-tree users (epf-test and epf-vntb).
  - Drop [PATCH v4 01/09] (dw-edma per-channel interrupt routing control)
    from this series for now, so the series focuses on what's needed by the
    current consumer (i.e. the doorbell fallback implementation).
  - Replace the v4 embedded-doorbell "test variant + host/kselftest
    plumbing" with a generic embedded-doorbell fallback in
    pci_epf_alloc_doorbell(), including exposing required IRQ request flags
    to EPF drivers.
  - Two preparatory fix patches (Patch 6/8 and 7/8) to clean up error
    handling and state management ahead of Patch 8/8.
  - Rename *_get_remote_resource() to *_get_aux_resources() and adjust
    relevant variable namings and kernel docs. Discussion may continue.
  - Rework dw-edma per-channel metadata exposure to cache the needed info
    in dw_edma_chip (IRQ number + emulation doorbell offset) and consume it
    from the DesignWare EPC auxiliary resource provider without calling back
    to dw-edma.

* v3->v4 changes:
  - Drop dma_slave_caps.hw_id and the dmaengine selfirq callback
    registration API. Instead, add a dw-edma specific dw_edma_chan_info()
    helper and extend the EPC remote resource metadata accordingly.
  - Add explicit acking for eDMA interrupt emulation and adjust the
    dw-edma IRQ path for embedded-doorbell usage.
  - Replace the previous EPC API smoke test with an embedded doorbell
    test variant (pci-epf-test + pci_endpoint_test/selftests).
  - Rebase onto pci.git controller/dwc commit 43d324eeb08c.

* v2->v3 changes:
  - Replace DWC-specific helpers with a generic EPC remote resource query API.
  - Add pci-epf-test smoke test and host/kselftest support for the new API.
  - Drop the dw-edma-specific notify-only channel and polling approach
    ([PATCH v2 4/7] and [PATCH v2 5/7]), and rework notification handling
    around a generic dmaengine_(un)register_selfirq() API implemented
    by dw-edma.

* v1->v2 changes:
  - Combine the two previously posted series into a single set (per Frank's
    suggestion). Order dmaengine/dw-edma patches first so hw_id support
    lands before the PCI LL-region helper, which assumes
    dma_slave_caps.hw_id availability.

v6: https://lore.kernel.org/all/20260209125316.2132589-1-den@valinux.co.jp/
v5: https://lore.kernel.org/all/20260209062952.2049053-1-den@valinux.co.jp/
v4: https://lore.kernel.org/all/20260206172646.1556847-1-den@valinux.co.jp/
v3: https://lore.kernel.org/all/20260204145440.950609-1-den@valinux.co.jp/
v2: https://lore.kernel.org/all/20260127033420.3460579-1-den@valinux.co.jp/
v1: https://lore.kernel.org/dmaengine/20260126073652.3293564-1-den@valinux.co.jp/
    +
    https://lore.kernel.org/linux-pci/20260126071550.3233631-1-den@valinux.co.jp/


Thanks for reviewing.

Many thanks to Frank and Niklas for the continued review and
constructive feedback throughout the development of this series.


Koichiro Den (9):
  PCI: endpoint: Describe reserved subregions within BARs
  PCI: dw-rockchip: Describe RK3588 BAR4 DMA ctrl window
  PCI: endpoint: Add auxiliary resource query API
  PCI: dwc: Record integrated eDMA register window
  PCI: dwc: ep: Expose integrated eDMA resources via EPC aux-resource
    API
  PCI: endpoint: pci-ep-msi: Refactor doorbell allocation for new
    backends
  PCI: endpoint: pci-epf-vntb: Reuse pre-exposed doorbells and IRQ flags
  PCI: endpoint: pci-epf-test: Reuse pre-exposed doorbell targets
  PCI: endpoint: pci-ep-msi: Add embedded eDMA doorbell fallback

 .../pci/controller/dwc/pcie-designware-ep.c   | 151 ++++++++++++++++++
 drivers/pci/controller/dwc/pcie-designware.c  |   4 +
 drivers/pci/controller/dwc/pcie-designware.h  |   2 +
 drivers/pci/controller/dwc/pcie-dw-rockchip.c |  15 +-
 drivers/pci/endpoint/functions/pci-epf-test.c |  87 ++++++----
 drivers/pci/endpoint/functions/pci-epf-vntb.c |  61 ++++++-
 drivers/pci/endpoint/pci-ep-msi.c             | 146 +++++++++++++++--
 drivers/pci/endpoint/pci-epc-core.c           |  41 +++++
 include/linux/pci-epc.h                       |  80 ++++++++++
 include/linux/pci-epf.h                       |  23 ++-
 10 files changed, 562 insertions(+), 48 deletions(-)

-- 
2.51.0

[PATCH v8 1/9] PCI: endpoint: Describe reserved subregions within BARs

[Koichiro Den]

Some endpoint controllers expose platform-owned, fixed register windows
within a BAR that EPF drivers must not reprogram (e.g. a BAR marked
BAR_RESERVED). Even in that case, EPF drivers may need to reference a
well-defined subset of that BAR, e.g. to reuse an integrated DMA
controller MMIO window as a doorbell target.

Introduce struct pci_epc_bar_rsvd_region and extend struct
pci_epc_bar_desc so EPC drivers can advertise such fixed subregions in a
controller-agnostic way.

No functional change for existing users.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 include/linux/pci-epc.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
index c021c7af175f..7a87f5962dd0 100644
--- a/include/linux/pci-epc.h
+++ b/include/linux/pci-epc.h
@@ -200,6 +200,30 @@ enum pci_epc_bar_type {
 	BAR_RESERVED,
 };
 
+/**
+ * enum pci_epc_bar_rsvd_region_type - type of a fixed subregion behind a BAR
+ * @PCI_EPC_BAR_RSVD_DMA_CTRL_MMIO: Integrated DMA controller MMIO window
+ *
+ * BARs marked BAR_RESERVED are owned by the SoC/EPC hardware and must not be
+ * reprogrammed by EPF drivers. Some of them still expose fixed subregions that
+ * EPFs may want to reference (e.g. embedded doorbell fallback).
+ */
+enum pci_epc_bar_rsvd_region_type {
+	PCI_EPC_BAR_RSVD_DMA_CTRL_MMIO = 0,
+};
+
+/**
+ * struct pci_epc_bar_rsvd_region - fixed subregion behind a BAR
+ * @type: reserved region type
+ * @offset: offset within the BAR aperture
+ * @size: size of the reserved region
+ */
+struct pci_epc_bar_rsvd_region {
+	enum pci_epc_bar_rsvd_region_type	type;
+	resource_size_t				offset;
+	resource_size_t				size;
+};
+
 /**
  * struct pci_epc_bar_desc - hardware description for a BAR
  * @type: the type of the BAR
@@ -213,11 +237,15 @@ enum pci_epc_bar_type {
  *		(If BARx is a 64-bit BAR that an EPF driver is not allowed to
  *		touch, then both BARx and BARx+1 must be set to type
  *		BAR_RESERVED.)
+ * @nr_rsvd_regions: number of fixed subregions described for BAR_RESERVED
+ * @rsvd_regions: fixed subregions behind BAR_RESERVED
  */
 struct pci_epc_bar_desc {
 	enum pci_epc_bar_type type;
 	u64 fixed_size;
 	bool only_64bit;
+	u8 nr_rsvd_regions;
+	const struct pci_epc_bar_rsvd_region *rsvd_regions;
 };
 
 /**
-- 
2.51.0

[PATCH v8 2/9] PCI: dw-rockchip: Describe RK3588 BAR4 DMA ctrl window

[Koichiro Den]

On RK3588 PCIe3_4L in EP mode, the integrated DMA controller registers
are permanently mapped to BAR4 and must not be repurposed by EPF
drivers.

When the remote peer needs to access these registers, it must use the
fixed BAR4 window instead of creating another inbound mapping in a
different BAR. Mixing the fixed window with an additional mapping can
lead to incorrect behavior.

Advertise the DMA controller MMIO window as a reserved BAR subregion so
EPF drivers can reuse it safely.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 drivers/pci/controller/dwc/pcie-dw-rockchip.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
index 5b17da63151d..ecc28093c589 100644
--- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
+++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
@@ -403,6 +403,15 @@ static const struct pci_epc_features rockchip_pcie_epc_features_rk3568 = {
 	.bar[BAR_5] = { .type = BAR_RESIZABLE, },
 };
 
+static const struct pci_epc_bar_rsvd_region rk3588_bar4_rsvd[] = {
+	{
+		/* DMA_CAP (BAR4: DMA Port Logic Structure) */
+		.type = PCI_EPC_BAR_RSVD_DMA_CTRL_MMIO,
+		.offset = 0x0,
+		.size = 0x2000,
+	},
+};
+
 /*
  * BAR4 on rk3588 exposes the ATU Port Logic Structure to the host regardless of
  * iATU settings for BAR4. This means that BAR4 cannot be used by an EPF driver,
@@ -420,7 +429,11 @@ static const struct pci_epc_features rockchip_pcie_epc_features_rk3588 = {
 	.bar[BAR_1] = { .type = BAR_RESIZABLE, },
 	.bar[BAR_2] = { .type = BAR_RESIZABLE, },
 	.bar[BAR_3] = { .type = BAR_RESIZABLE, },
-	.bar[BAR_4] = { .type = BAR_RESERVED, },
+	.bar[BAR_4] = {
+		.type = BAR_RESERVED,
+		.nr_rsvd_regions = ARRAY_SIZE(rk3588_bar4_rsvd),
+		.rsvd_regions = rk3588_bar4_rsvd,
+	},
 	.bar[BAR_5] = { .type = BAR_RESIZABLE, },
 };
 
-- 
2.51.0

[PATCH v8 3/9] PCI: endpoint: Add auxiliary resource query API

[Koichiro Den]

Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
engines) whose register windows and descriptor memories metadata need to
be exposed to a remote peer. Endpoint function drivers need a generic
way to discover such resources without hard-coding controller-specific
helpers.

Add pci_epc_get_aux_resources() and the corresponding pci_epc_ops
get_aux_resources() callback. The API returns a list of resources
described by type, physical address and size, plus type-specific
metadata.

Passing resources == NULL (or num_resources == 0) returns the required
number of entries.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
Changes since v7:
  - Add a 'data' field in pci_epc_aux_resource.u.db_mmio.
  - Add comments describing the type-specific metadata fields.

 drivers/pci/endpoint/pci-epc-core.c | 41 +++++++++++++++++++++++
 include/linux/pci-epc.h             | 52 +++++++++++++++++++++++++++++
 2 files changed, 93 insertions(+)

diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
index 068155819c57..01de4bd5047a 100644
--- a/drivers/pci/endpoint/pci-epc-core.c
+++ b/drivers/pci/endpoint/pci-epc-core.c
@@ -155,6 +155,47 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
 }
 EXPORT_SYMBOL_GPL(pci_epc_get_features);
 
+/**
+ * pci_epc_get_aux_resources() - query EPC-provided auxiliary resources
+ * @epc: EPC device
+ * @func_no: function number
+ * @vfunc_no: virtual function number
+ * @resources: output array (may be NULL to query required count)
+ * @num_resources: size of @resources array in entries (0 when querying count)
+ *
+ * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
+ * registers and/or descriptor memories can be exposed to the host by mapping
+ * them into BAR space. This helper queries the backend for such resources.
+ *
+ * Return:
+ *   * >= 0: number of resources returned (or required, if @resources is NULL)
+ *   * -EOPNOTSUPP: backend does not support auxiliary resource queries
+ *   * other -errno on failure
+ */
+int pci_epc_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+			      struct pci_epc_aux_resource *resources,
+			      int num_resources)
+{
+	int ret;
+
+	if (!epc || !epc->ops)
+		return -EINVAL;
+
+	if (func_no >= epc->max_functions)
+		return -EINVAL;
+
+	if (!epc->ops->get_aux_resources)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&epc->lock);
+	ret = epc->ops->get_aux_resources(epc, func_no, vfunc_no, resources,
+					  num_resources);
+	mutex_unlock(&epc->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pci_epc_get_aux_resources);
+
 /**
  * pci_epc_stop() - stop the PCI link
  * @epc: the link of the EPC device that has to be stopped
diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
index 7a87f5962dd0..c68aaaf3542a 100644
--- a/include/linux/pci-epc.h
+++ b/include/linux/pci-epc.h
@@ -61,6 +61,51 @@ struct pci_epc_map {
 	void __iomem	*virt_addr;
 };
 
+/**
+ * enum pci_epc_aux_resource_type - auxiliary resource type identifiers
+ * @PCI_EPC_AUX_DMA_CTRL_MMIO: Integrated DMA controller register window (MMIO)
+ * @PCI_EPC_AUX_DMA_CHAN_DESC: Per-channel DMA descriptor
+ * @PCI_EPC_AUX_DOORBELL_MMIO: Doorbell MMIO, that might be outside the DMA
+ *                             controller register window
+ *
+ * EPC backends may expose auxiliary blocks (e.g. DMA engines) by mapping their
+ * register windows and descriptor memories into BAR space. This enum
+ * identifies the type of each exposable resource.
+ */
+enum pci_epc_aux_resource_type {
+	PCI_EPC_AUX_DMA_CTRL_MMIO,
+	PCI_EPC_AUX_DMA_CHAN_DESC,
+	PCI_EPC_AUX_DOORBELL_MMIO,
+};
+
+/**
+ * struct pci_epc_aux_resource - a physical auxiliary resource that may be
+ *                               exposed for peer use
+ * @type:       resource type, see enum pci_epc_aux_resource_type
+ * @phys_addr:  physical base address of the resource
+ * @size:       size of the resource in bytes
+ * @bar:        BAR number where this resource is already exposed to the RC
+ *              (NO_BAR if not)
+ * @bar_offset: offset within @bar where the resource starts (valid iff
+ *              @bar != NO_BAR)
+ * @u:          type-specific metadata
+ */
+struct pci_epc_aux_resource {
+	enum pci_epc_aux_resource_type type;
+	phys_addr_t phys_addr;
+	resource_size_t size;
+	enum pci_barno bar;
+	resource_size_t bar_offset;
+
+	union {
+		/* PCI_EPC_AUX_DOORBELL_MMIO */
+		struct {
+			int irq; /* IRQ number for the doorbell handler */
+			u32 data; /* write value to ring the doorbell */
+		} db_mmio;
+	} u;
+};
+
 /**
  * struct pci_epc_ops - set of function pointers for performing EPC operations
  * @write_header: ops to populate configuration space header
@@ -84,6 +129,7 @@ struct pci_epc_map {
  * @start: ops to start the PCI link
  * @stop: ops to stop the PCI link
  * @get_features: ops to get the features supported by the EPC
+ * @get_aux_resources: ops to retrieve controller-owned auxiliary resources
  * @owner: the module owner containing the ops
  */
 struct pci_epc_ops {
@@ -115,6 +161,9 @@ struct pci_epc_ops {
 	void	(*stop)(struct pci_epc *epc);
 	const struct pci_epc_features* (*get_features)(struct pci_epc *epc,
 						       u8 func_no, u8 vfunc_no);
+	int	(*get_aux_resources)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+				     struct pci_epc_aux_resource *resources,
+				     int num_resources);
 	struct module *owner;
 };
 
@@ -337,6 +386,9 @@ int pci_epc_start(struct pci_epc *epc);
 void pci_epc_stop(struct pci_epc *epc);
 const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
 						    u8 func_no, u8 vfunc_no);
+int pci_epc_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+			      struct pci_epc_aux_resource *resources,
+			      int num_resources);
 enum pci_barno
 pci_epc_get_first_free_bar(const struct pci_epc_features *epc_features);
 enum pci_barno pci_epc_get_next_free_bar(const struct pci_epc_features
-- 
2.51.0

[PATCH v8 4/9] PCI: dwc: Record integrated eDMA register window

[Koichiro Den]

Some DesignWare PCIe controllers integrate an eDMA block whose registers
are located in a dedicated register window. Endpoint function drivers
may need the physical base and size of this window to map/expose it to a
peer.

Record the physical base and size of the integrated eDMA register window
in struct dw_pcie.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 drivers/pci/controller/dwc/pcie-designware.c | 4 ++++
 drivers/pci/controller/dwc/pcie-designware.h | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 5741c09dde7f..f82ed189f6ae 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -162,8 +162,12 @@ int dw_pcie_get_resources(struct dw_pcie *pci)
 			pci->edma.reg_base = devm_ioremap_resource(pci->dev, res);
 			if (IS_ERR(pci->edma.reg_base))
 				return PTR_ERR(pci->edma.reg_base);
+			pci->edma_reg_phys = res->start;
+			pci->edma_reg_size = resource_size(res);
 		} else if (pci->atu_size >= 2 * DEFAULT_DBI_DMA_OFFSET) {
 			pci->edma.reg_base = pci->atu_base + DEFAULT_DBI_DMA_OFFSET;
+			pci->edma_reg_phys = pci->atu_phys_addr + DEFAULT_DBI_DMA_OFFSET;
+			pci->edma_reg_size = pci->atu_size - DEFAULT_DBI_DMA_OFFSET;
 		}
 	}
 
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index ae6389dd9caa..52f26663e8b1 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -541,6 +541,8 @@ struct dw_pcie {
 	int			max_link_speed;
 	u8			n_fts[2];
 	struct dw_edma_chip	edma;
+	phys_addr_t		edma_reg_phys;
+	resource_size_t		edma_reg_size;
 	bool			l1ss_support;	/* L1 PM Substates support */
 	struct clk_bulk_data	app_clks[DW_PCIE_NUM_APP_CLKS];
 	struct clk_bulk_data	core_clks[DW_PCIE_NUM_CORE_CLKS];
-- 
2.51.0

[PATCH v8 5/9] PCI: dwc: ep: Expose integrated eDMA resources via EPC aux-resource API

[Koichiro Den]

Implement the EPC aux-resource API for DesignWare endpoint controllers
with integrated eDMA.

Report:
  - DMA controller MMIO window (PCI_EPC_AUX_DMA_CTRL_MMIO)
  - interrupt-emulation doorbell register (PCI_EPC_AUX_DOORBELL_MMIO),
    including its Linux IRQ and the data value to write to trigger the
    interrupt
  - per-channel LL descriptor regions (PCI_EPC_AUX_DMA_CHAN_DESC)

If the DMA controller MMIO window is already exposed via a
platform-owned fixed BAR subregion, also provide the BAR number and
offset so EPF drivers can reuse it without reprogramming the BAR.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
Changes since v7:
  - Use range_end_overflows_t() instead of an open-coded overflow check.
  - Make it explicit that the write data is 0 for dw-edma.

 .../pci/controller/dwc/pcie-designware-ep.c   | 151 ++++++++++++++++++
 1 file changed, 151 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 7e7844ff0f7e..22b6777d520f 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -9,6 +9,7 @@
 #include <linux/align.h>
 #include <linux/bitfield.h>
 #include <linux/of.h>
+#include <linux/overflow.h>
 #include <linux/platform_device.h>
 
 #include "pcie-designware.h"
@@ -808,6 +809,155 @@ dw_pcie_ep_get_features(struct pci_epc *epc, u8 func_no, u8 vfunc_no)
 	return ep->ops->get_features(ep);
 }
 
+static const struct pci_epc_bar_rsvd_region *
+dw_pcie_ep_find_bar_rsvd_region(struct dw_pcie_ep *ep,
+				enum pci_epc_bar_rsvd_region_type type,
+				enum pci_barno *bar,
+				resource_size_t *bar_offset)
+{
+	const struct pci_epc_features *features;
+	const struct pci_epc_bar_desc *bar_desc;
+	const struct pci_epc_bar_rsvd_region *r;
+	int i, j;
+
+	if (!ep->ops->get_features)
+		return NULL;
+
+	features = ep->ops->get_features(ep);
+	if (!features)
+		return NULL;
+
+	for (i = BAR_0; i <= BAR_5; i++) {
+		bar_desc = &features->bar[i];
+
+		if (!bar_desc->nr_rsvd_regions || !bar_desc->rsvd_regions)
+			continue;
+
+		for (j = 0; j < bar_desc->nr_rsvd_regions; j++) {
+			r = &bar_desc->rsvd_regions[j];
+
+			if (r->type != type)
+				continue;
+
+			if (bar)
+				*bar = i;
+			if (bar_offset)
+				*bar_offset = r->offset;
+			return r;
+		}
+	}
+
+	return NULL;
+}
+
+static int
+dw_pcie_ep_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+			     struct pci_epc_aux_resource *resources,
+			     int num_resources)
+{
+	struct dw_pcie_ep *ep = epc_get_drvdata(epc);
+	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
+	const struct pci_epc_bar_rsvd_region *rsvd;
+	struct dw_edma_chip *edma = &pci->edma;
+	enum pci_barno dma_ctrl_bar = NO_BAR;
+	int ll_cnt = 0, needed, idx = 0;
+	resource_size_t db_offset = edma->db_offset;
+	resource_size_t dma_ctrl_bar_offset = 0;
+	resource_size_t dma_reg_size;
+	unsigned int i;
+
+	if (!pci->edma_reg_size)
+		return 0;
+
+	dma_reg_size = pci->edma_reg_size;
+
+	for (i = 0; i < edma->ll_wr_cnt; i++)
+		if (edma->ll_region_wr[i].sz)
+			ll_cnt++;
+
+	for (i = 0; i < edma->ll_rd_cnt; i++)
+		if (edma->ll_region_rd[i].sz)
+			ll_cnt++;
+
+	needed = 1 + ll_cnt + (db_offset != ~0 ? 1 : 0);
+
+	/* Count query mode */
+	if (!resources || !num_resources)
+		return needed;
+
+	if (num_resources < needed)
+		return -ENOSPC;
+
+	rsvd = dw_pcie_ep_find_bar_rsvd_region(ep,
+					       PCI_EPC_BAR_RSVD_DMA_CTRL_MMIO,
+					       &dma_ctrl_bar,
+					       &dma_ctrl_bar_offset);
+	if (rsvd && rsvd->size < dma_reg_size)
+		dma_reg_size = rsvd->size;
+
+	/* DMA register block */
+	resources[idx++] = (struct pci_epc_aux_resource) {
+		.type = PCI_EPC_AUX_DMA_CTRL_MMIO,
+		.phys_addr = pci->edma_reg_phys,
+		.size = dma_reg_size,
+		.bar = dma_ctrl_bar,
+		.bar_offset = dma_ctrl_bar_offset,
+	};
+
+	/*
+	 * For interrupt-emulation doorbells, report a standalone resource
+	 * instead of bundling it into the DMA controller MMIO resource.
+	 */
+	if (db_offset != ~0) {
+		if (range_end_overflows_t(resource_size_t, db_offset,
+					  sizeof(u32), dma_reg_size))
+			return -EINVAL;
+
+		resources[idx++] = (struct pci_epc_aux_resource) {
+			.type = PCI_EPC_AUX_DOORBELL_MMIO,
+			.phys_addr = pci->edma_reg_phys + db_offset,
+			.size = sizeof(u32),
+			.bar = dma_ctrl_bar,
+			.bar_offset = dma_ctrl_bar != NO_BAR ?
+					dma_ctrl_bar_offset + db_offset : 0,
+			.u.db_mmio = {
+				.irq = edma->db_irq,
+				.data = 0, /* write 0 to assert */
+			},
+		};
+	}
+
+	/* One LL region per write channel */
+	for (i = 0; i < edma->ll_wr_cnt; i++) {
+		if (!edma->ll_region_wr[i].sz)
+			continue;
+
+		resources[idx++] = (struct pci_epc_aux_resource) {
+			.type = PCI_EPC_AUX_DMA_CHAN_DESC,
+			.phys_addr = edma->ll_region_wr[i].paddr,
+			.size = edma->ll_region_wr[i].sz,
+			.bar = NO_BAR,
+			.bar_offset = 0,
+		};
+	}
+
+	/* One LL region per read channel */
+	for (i = 0; i < edma->ll_rd_cnt; i++) {
+		if (!edma->ll_region_rd[i].sz)
+			continue;
+
+		resources[idx++] = (struct pci_epc_aux_resource) {
+			.type = PCI_EPC_AUX_DMA_CHAN_DESC,
+			.phys_addr = edma->ll_region_rd[i].paddr,
+			.size = edma->ll_region_rd[i].sz,
+			.bar = NO_BAR,
+			.bar_offset = 0,
+		};
+	}
+
+	return idx;
+}
+
 static const struct pci_epc_ops epc_ops = {
 	.write_header		= dw_pcie_ep_write_header,
 	.set_bar		= dw_pcie_ep_set_bar,
@@ -823,6 +973,7 @@ static const struct pci_epc_ops epc_ops = {
 	.start			= dw_pcie_ep_start,
 	.stop			= dw_pcie_ep_stop,
 	.get_features		= dw_pcie_ep_get_features,
+	.get_aux_resources	= dw_pcie_ep_get_aux_resources,
 };
 
 /**
-- 
2.51.0

[PATCH v8 6/9] PCI: endpoint: pci-ep-msi: Refactor doorbell allocation for new backends

[Koichiro Den]

Prepare pci-ep-msi for non-MSI doorbell backends.

Factor MSI doorbell allocation into a helper and extend struct
pci_epf_doorbell_msg with:

  - irq_flags: required IRQ request flags (e.g. IRQF_SHARED for some
    backends)
  - type: doorbell backend type
  - bar/offset: pre-exposed doorbell target location, if any

Initialize these fields for the existing MSI-backed doorbell
implementation.

Also add PCI_EPF_DOORBELL_EMBEDDED type, which is to be implemented in a
follow-up patch.

No functional changes.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
Changes since v7:
  - Switch to designated initializer and rely on implicit
    zero-initialization.

 drivers/pci/endpoint/pci-ep-msi.c | 54 ++++++++++++++++++++++---------
 include/linux/pci-epf.h           | 23 +++++++++++--
 2 files changed, 60 insertions(+), 17 deletions(-)

diff --git a/drivers/pci/endpoint/pci-ep-msi.c b/drivers/pci/endpoint/pci-ep-msi.c
index ad8a81d6ad77..50badffa9d72 100644
--- a/drivers/pci/endpoint/pci-ep-msi.c
+++ b/drivers/pci/endpoint/pci-ep-msi.c
@@ -8,6 +8,7 @@
 
 #include <linux/device.h>
 #include <linux/export.h>
+#include <linux/interrupt.h>
 #include <linux/irqdomain.h>
 #include <linux/module.h>
 #include <linux/msi.h>
@@ -35,23 +36,13 @@ static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
 	pci_epc_put(epc);
 }
 
-int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
+static int pci_epf_alloc_doorbell_msi(struct pci_epf *epf, u16 num_db)
 {
-	struct pci_epc *epc = epf->epc;
+	struct pci_epf_doorbell_msg *msg;
 	struct device *dev = &epf->dev;
+	struct pci_epc *epc = epf->epc;
 	struct irq_domain *domain;
-	void *msg;
-	int ret;
-	int i;
-
-	/* TODO: Multi-EPF support */
-	if (list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list) != epf) {
-		dev_err(dev, "MSI doorbell doesn't support multiple EPF\n");
-		return -EINVAL;
-	}
-
-	if (epf->db_msg)
-		return -EBUSY;
+	int ret, i;
 
 	domain = of_msi_map_get_device_domain(epc->dev.parent, 0,
 					      DOMAIN_BUS_PLATFORM_MSI);
@@ -74,6 +65,12 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
 	if (!msg)
 		return -ENOMEM;
 
+	for (i = 0; i < num_db; i++)
+		msg[i] = (struct pci_epf_doorbell_msg) {
+			.type = PCI_EPF_DOORBELL_MSI,
+			.bar = NO_BAR,
+		};
+
 	epf->num_db = num_db;
 	epf->db_msg = msg;
 
@@ -90,13 +87,40 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
 	for (i = 0; i < num_db; i++)
 		epf->db_msg[i].virq = msi_get_virq(epc->dev.parent, i);
 
+	return 0;
+}
+
+int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
+{
+	struct pci_epc *epc = epf->epc;
+	struct device *dev = &epf->dev;
+	int ret;
+
+	/* TODO: Multi-EPF support */
+	if (list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list) != epf) {
+		dev_err(dev, "Doorbell doesn't support multiple EPF\n");
+		return -EINVAL;
+	}
+
+	if (epf->db_msg)
+		return -EBUSY;
+
+	ret = pci_epf_alloc_doorbell_msi(epf, num_db);
+	if (!ret)
+		return 0;
+
+	dev_err(dev, "Failed to allocate doorbell: %d\n", ret);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);
 
 void pci_epf_free_doorbell(struct pci_epf *epf)
 {
-	platform_device_msi_free_irqs_all(epf->epc->dev.parent);
+	if (!epf->db_msg)
+		return;
+
+	if (epf->db_msg[0].type == PCI_EPF_DOORBELL_MSI)
+		platform_device_msi_free_irqs_all(epf->epc->dev.parent);
 
 	kfree(epf->db_msg);
 	epf->db_msg = NULL;
diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
index 7737a7c03260..cd747447a1ea 100644
--- a/include/linux/pci-epf.h
+++ b/include/linux/pci-epf.h
@@ -152,14 +152,33 @@ struct pci_epf_bar {
 	struct pci_epf_bar_submap	*submap;
 };
 
+enum pci_epf_doorbell_type {
+	PCI_EPF_DOORBELL_MSI = 0,
+	PCI_EPF_DOORBELL_EMBEDDED,
+};
+
 /**
  * struct pci_epf_doorbell_msg - represents doorbell message
- * @msg: MSI message
- * @virq: IRQ number of this doorbell MSI message
+ * @msg: Doorbell address/data pair to be mapped into BAR space.
+ *       For MSI-backed doorbells this is the MSI message, while for
+ *       "embedded" doorbells this represents an MMIO write that asserts
+ *       an interrupt on the EP side.
+ * @virq: IRQ number of this doorbell message
+ * @irq_flags: Required flags for request_irq()/request_threaded_irq().
+ *             Callers may OR-in additional flags (e.g. IRQF_ONESHOT).
+ * @type: Doorbell type.
+ * @bar: BAR number where the doorbell target is already exposed to the RC
+ *       (NO_BAR if not)
+ * @offset: offset within @bar for the doorbell target (valid iff
+ *          @bar != NO_BAR)
  */
 struct pci_epf_doorbell_msg {
 	struct msi_msg msg;
 	int virq;
+	unsigned long irq_flags;
+	enum pci_epf_doorbell_type type;
+	enum pci_barno bar;
+	resource_size_t offset;
 };
 
 /**
-- 
2.51.0

[PATCH v8 7/9] PCI: endpoint: pci-epf-vntb: Reuse pre-exposed doorbells and IRQ flags

[Koichiro Den]

Support doorbell backends where the doorbell target is already exposed
via a platform-owned fixed BAR mapping and/or where the doorbell IRQ
must be requested with specific flags.

When pci_epf_alloc_doorbell() provides db_msg[].bar/offset, reuse the
pre-exposed BAR window and skip programming a new inbound mapping. Also
honor db_msg[].irq_flags when requesting the doorbell IRQ.

Multiple doorbells may share the same Linux IRQ. Avoid duplicate
request_irq() calls by requesting each unique virq once.

This makes pci-epf-vntb work with platform-defined or embedded doorbell
backends without exposing backend-specific details to the consumer
layer.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
Changes since v7:
  - Deduplicate request_irq()/free_irq() calls based on virq (shared
    IRQ) rather than doorbell type.

 drivers/pci/endpoint/functions/pci-epf-vntb.c | 61 ++++++++++++++++++-
 1 file changed, 58 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index 52cf442ca1d9..b1e8414c4e43 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -134,6 +134,11 @@ struct epf_ntb {
 	u16 vntb_vid;
 
 	bool linkup;
+
+	/*
+	 * True when doorbells are interrupt-driven (MSI or embedded), false
+	 * when polled.
+	 */
 	bool msi_doorbell;
 	u32 spad_size;
 
@@ -517,6 +522,17 @@ static int epf_ntb_configure_interrupt(struct epf_ntb *ntb)
 	return 0;
 }
 
+static bool epf_ntb_db_irq_is_first(const struct pci_epf *epf, unsigned int idx)
+{
+	unsigned int i;
+
+	for (i = 0; i < idx; i++)
+		if (epf->db_msg[i].virq == epf->db_msg[idx].virq)
+			return false;
+
+	return true;
+}
+
 static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
 					    struct pci_epf_bar *db_bar,
 					    const struct pci_epc_features *epc_features,
@@ -533,9 +549,24 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
 	if (ret)
 		return ret;
 
+	/*
+	 * The doorbell target may already be exposed by a platform-owned fixed
+	 * BAR. In that case, we must reuse it and the requested db_bar must
+	 * match.
+	 */
+	if (epf->db_msg[0].bar != NO_BAR && epf->db_msg[0].bar != barno) {
+		ret = -EINVAL;
+		goto err_free_doorbell;
+	}
+
 	for (req = 0; req < ntb->db_count; req++) {
+		/* Avoid requesting duplicate handlers */
+		if (!epf_ntb_db_irq_is_first(epf, req))
+			continue;
+
 		ret = request_irq(epf->db_msg[req].virq, epf_ntb_doorbell_handler,
-				  0, "pci_epf_vntb_db", ntb);
+				  epf->db_msg[req].irq_flags, "pci_epf_vntb_db",
+				  ntb);
 
 		if (ret) {
 			dev_err(&epf->dev,
@@ -545,6 +576,22 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
 		}
 	}
 
+	if (epf->db_msg[0].bar != NO_BAR) {
+		for (i = 0; i < ntb->db_count; i++) {
+			msg = &epf->db_msg[i].msg;
+
+			if (epf->db_msg[i].bar != barno) {
+				ret = -EINVAL;
+				goto err_free_irq;
+			}
+
+			ntb->reg->db_data[i] = msg->data;
+			ntb->reg->db_offset[i] = epf->db_msg[i].offset;
+		}
+		goto out;
+	}
+
+	/* Program inbound mapping for the doorbell */
 	msg = &epf->db_msg[0].msg;
 
 	high = 0;
@@ -591,6 +638,7 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
 		ntb->reg->db_offset[i] = offset;
 	}
 
+out:
 	ntb->reg->db_entry_size = 0;
 
 	ntb->msi_doorbell = true;
@@ -598,9 +646,13 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
 	return 0;
 
 err_free_irq:
-	for (req--; req >= 0; req--)
+	for (req--; req >= 0; req--) {
+		if (!epf_ntb_db_irq_is_first(epf, req))
+			continue;
 		free_irq(epf->db_msg[req].virq, ntb);
+	}
 
+err_free_doorbell:
 	pci_epf_free_doorbell(ntb->epf);
 	return ret;
 }
@@ -666,8 +718,11 @@ static void epf_ntb_db_bar_clear(struct epf_ntb *ntb)
 	if (ntb->msi_doorbell) {
 		int i;
 
-		for (i = 0; i < ntb->db_count; i++)
+		for (i = 0; i < ntb->db_count; i++) {
+			if (!epf_ntb_db_irq_is_first(ntb->epf, i))
+				continue;
 			free_irq(ntb->epf->db_msg[i].virq, ntb);
+		}
 	}
 
 	if (ntb->epf->db_msg)
-- 
2.51.0

[PATCH v8 8/9] PCI: endpoint: pci-epf-test: Reuse pre-exposed doorbell targets

[Koichiro Den]

pci-epf-test advertises the doorbell target to the RC as a BAR number
and an offset, and the RC rings the doorbell with a single DWORD MMIO
write.

Some doorbell backends may report that the doorbell target is already
exposed via a platform-owned fixed BAR (db_msg[0].bar/offset). In that
case, reuse the pre-exposed window and do not reprogram the BAR with
pci_epc_set_bar().

Also honor db_msg[0].irq_flags when requesting the doorbell IRQ, and
only restore the original BAR mapping on disable if pci-epf-test
programmed it.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 drivers/pci/endpoint/functions/pci-epf-test.c | 87 +++++++++++++------
 1 file changed, 60 insertions(+), 27 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index 12705858e502..f5a74108e180 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -86,6 +86,7 @@ struct pci_epf_test {
 	bool			dma_private;
 	const struct pci_epc_features *epc_features;
 	struct pci_epf_bar	db_bar;
+	bool			db_bar_programmed;
 	size_t			bar_size[PCI_STD_NUM_BARS];
 };
 
@@ -725,7 +726,9 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
 {
 	u32 status = le32_to_cpu(reg->status);
 	struct pci_epf *epf = epf_test->epf;
+	struct pci_epf_doorbell_msg *db;
 	struct pci_epc *epc = epf->epc;
+	unsigned long irq_flags;
 	struct msi_msg *msg;
 	enum pci_barno bar;
 	size_t offset;
@@ -735,13 +738,28 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
 	if (ret)
 		goto set_status_err;
 
-	msg = &epf->db_msg[0].msg;
-	bar = pci_epc_get_next_free_bar(epf_test->epc_features, epf_test->test_reg_bar + 1);
-	if (bar < BAR_0)
-		goto err_doorbell_cleanup;
+	db = &epf->db_msg[0];
+	msg = &db->msg;
+	epf_test->db_bar_programmed = false;
+
+	if (db->bar != NO_BAR) {
+		/*
+		 * The doorbell target is already exposed via a platform-owned
+		 * fixed BAR
+		 */
+		bar = db->bar;
+		offset = db->offset;
+	} else {
+		bar = pci_epc_get_next_free_bar(epf_test->epc_features,
+						epf_test->test_reg_bar + 1);
+		if (bar < BAR_0)
+			goto err_doorbell_cleanup;
+	}
+
+	irq_flags = epf->db_msg[0].irq_flags | IRQF_ONESHOT;
 
 	ret = request_threaded_irq(epf->db_msg[0].virq, NULL,
-				   pci_epf_test_doorbell_handler, IRQF_ONESHOT,
+				   pci_epf_test_doorbell_handler, irq_flags,
 				   "pci-ep-test-doorbell", epf_test);
 	if (ret) {
 		dev_err(&epf->dev,
@@ -753,22 +771,33 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
 	reg->doorbell_data = cpu_to_le32(msg->data);
 	reg->doorbell_bar = cpu_to_le32(bar);
 
-	msg = &epf->db_msg[0].msg;
-	ret = pci_epf_align_inbound_addr(epf, bar, ((u64)msg->address_hi << 32) | msg->address_lo,
-					 &epf_test->db_bar.phys_addr, &offset);
+	if (db->bar == NO_BAR) {
+		ret = pci_epf_align_inbound_addr(epf, bar,
+						 ((u64)msg->address_hi << 32) |
+						 msg->address_lo,
+						 &epf_test->db_bar.phys_addr,
+						 &offset);
 
-	if (ret)
-		goto err_free_irq;
+		if (ret)
+			goto err_free_irq;
+	}
+
+	if (size_add(offset, sizeof(u32)) > epf->bar[bar].size)
+		goto err_doorbell_cleanup;
 
 	reg->doorbell_offset = cpu_to_le32(offset);
 
-	epf_test->db_bar.barno = bar;
-	epf_test->db_bar.size = epf->bar[bar].size;
-	epf_test->db_bar.flags = epf->bar[bar].flags;
+	if (db->bar == NO_BAR) {
+		epf_test->db_bar.barno = bar;
+		epf_test->db_bar.size = epf->bar[bar].size;
+		epf_test->db_bar.flags = epf->bar[bar].flags;
 
-	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf_test->db_bar);
-	if (ret)
-		goto err_free_irq;
+		ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf_test->db_bar);
+		if (ret)
+			goto err_free_irq;
+
+		epf_test->db_bar_programmed = true;
+	}
 
 	status |= STATUS_DOORBELL_ENABLE_SUCCESS;
 	reg->status = cpu_to_le32(status);
@@ -798,17 +827,21 @@ static void pci_epf_test_disable_doorbell(struct pci_epf_test *epf_test,
 	free_irq(epf->db_msg[0].virq, epf_test);
 	pci_epf_test_doorbell_cleanup(epf_test);
 
-	/*
-	 * The doorbell feature temporarily overrides the inbound translation
-	 * to point to the address stored in epf_test->db_bar.phys_addr, i.e.,
-	 * it calls set_bar() twice without ever calling clear_bar(), as
-	 * calling clear_bar() would clear the BAR's PCI address assigned by
-	 * the host. Thus, when disabling the doorbell, restore the inbound
-	 * translation to point to the memory allocated for the BAR.
-	 */
-	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf->bar[bar]);
-	if (ret)
-		goto set_status_err;
+	if (epf_test->db_bar_programmed) {
+		/*
+		 * The doorbell feature temporarily overrides the inbound translation
+		 * to point to the address stored in epf_test->db_bar.phys_addr, i.e.,
+		 * it calls set_bar() twice without ever calling clear_bar(), as
+		 * calling clear_bar() would clear the BAR's PCI address assigned by
+		 * the host. Thus, when disabling the doorbell, restore the inbound
+		 * translation to point to the memory allocated for the BAR.
+		 */
+		ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf->bar[bar]);
+		if (ret)
+			goto set_status_err;
+
+		epf_test->db_bar_programmed = false;
+	}
 
 	status |= STATUS_DOORBELL_DISABLE_SUCCESS;
 	reg->status = cpu_to_le32(status);
-- 
2.51.0

[PATCH v8 9/9] PCI: endpoint: pci-ep-msi: Add embedded eDMA doorbell fallback

[Koichiro Den]

Some endpoint platforms cannot use platform MSI / GIC ITS to implement
EP-side doorbells. In those cases, EPF drivers cannot provide an
interrupt-driven doorbell and often fall back to polling.

Add an "embedded" doorbell backend that uses a controller-integrated
doorbell target (e.g. DesignWare integrated eDMA interrupt-emulation
doorbell).

The backend locates the doorbell register and a corresponding Linux IRQ
via the EPC aux-resource API. If the doorbell register is already
exposed via a fixed BAR mapping, provide BAR+offset. Otherwise provide
the physical address so EPF drivers can map it into BAR space.

When MSI doorbell allocation fails with -ENODEV,
pci_epf_alloc_doorbell() falls back to this embedded backend.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
Changes since v7:
  - Use designated initializer for consistent styling.
  - Clean up the pci_epf_alloc_doorbell() error path.

 drivers/pci/endpoint/pci-ep-msi.c | 96 ++++++++++++++++++++++++++++++-
 1 file changed, 94 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/endpoint/pci-ep-msi.c b/drivers/pci/endpoint/pci-ep-msi.c
index 50badffa9d72..66f5a68c81b0 100644
--- a/drivers/pci/endpoint/pci-ep-msi.c
+++ b/drivers/pci/endpoint/pci-ep-msi.c
@@ -6,6 +6,7 @@
  * Author: Frank Li <Frank.Li@nxp.com>
  */
 
+#include <linux/cleanup.h>
 #include <linux/device.h>
 #include <linux/export.h>
 #include <linux/interrupt.h>
@@ -36,6 +37,84 @@ static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
 	pci_epc_put(epc);
 }
 
+static int pci_epf_alloc_doorbell_embedded(struct pci_epf *epf, u16 num_db)
+{
+	const struct pci_epc_aux_resource *doorbell = NULL;
+	struct pci_epf_doorbell_msg *msg;
+	struct pci_epc *epc = epf->epc;
+	struct device *dev = &epf->dev;
+	int count, ret, i;
+	u64 addr;
+
+	count = pci_epc_get_aux_resources(epc, epf->func_no, epf->vfunc_no,
+					  NULL, 0);
+	if (count == -EOPNOTSUPP || count == 0)
+		return -ENODEV;
+	if (count < 0)
+		return count;
+
+	struct pci_epc_aux_resource *res __free(kfree) =
+				kcalloc(count, sizeof(*res), GFP_KERNEL);
+	if (!res)
+		return -ENOMEM;
+
+	ret = pci_epc_get_aux_resources(epc, epf->func_no, epf->vfunc_no,
+					res, count);
+	if (ret == -EOPNOTSUPP || ret == 0)
+		return -ENODEV;
+	if (ret < 0)
+		return ret;
+
+	count = ret;
+
+	for (i = 0; i < count; i++) {
+		if (res[i].type == PCI_EPC_AUX_DOORBELL_MMIO) {
+			if (doorbell) {
+				dev_warn(dev,
+					 "Duplicate DOORBELL_MMIO resource found\n");
+				continue;
+			}
+			doorbell = &res[i];
+		}
+	}
+	if (!doorbell)
+		return -ENODEV;
+
+	msg = kcalloc(num_db, sizeof(*msg), GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	addr = doorbell->phys_addr;
+
+	/*
+	 * Embedded doorbell backends (e.g. DesignWare eDMA interrupt emulation)
+	 * typically provide a single IRQ and do not offer per-doorbell
+	 * distinguishable address/data pairs. The EPC aux resource therefore
+	 * exposes one DOORBELL_MMIO entry (u.db_mmio.irq).
+	 *
+	 * Still, pci_epf_alloc_doorbell() allows requesting multiple doorbells.
+	 * For such backends we replicate the same address/data for each entry
+	 * and mark the IRQ as shared (IRQF_SHARED). Consumers must treat them
+	 * as equivalent "kick" doorbells.
+	 */
+	for (i = 0; i < num_db; i++)
+		msg[i] = (struct pci_epf_doorbell_msg) {
+			.msg.address_lo = (u32)addr,
+			.msg.address_hi = (u32)(addr >> 32),
+			.msg.data = doorbell->u.db_mmio.data,
+			.virq = doorbell->u.db_mmio.irq,
+			.irq_flags = IRQF_SHARED,
+			.type = PCI_EPF_DOORBELL_EMBEDDED,
+			.bar = doorbell->bar,
+			.offset = (doorbell->bar == NO_BAR) ? 0 :
+				  doorbell->bar_offset,
+		};
+
+	epf->num_db = num_db;
+	epf->db_msg = msg;
+	return 0;
+}
+
 static int pci_epf_alloc_doorbell_msi(struct pci_epf *epf, u16 num_db)
 {
 	struct pci_epf_doorbell_msg *msg;
@@ -109,8 +188,21 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
 	if (!ret)
 		return 0;
 
-	dev_err(dev, "Failed to allocate doorbell: %d\n", ret);
-	return ret;
+	/*
+	 * Fall back to embedded doorbell only when platform MSI is unavailable
+	 * for this EPC.
+	 */
+	if (ret != -ENODEV)
+		return ret;
+
+	ret = pci_epf_alloc_doorbell_embedded(epf, num_db);
+	if (ret) {
+		dev_err(dev, "Failed to allocate doorbell: %d\n", ret);
+		return ret;
+	}
+
+	dev_info(dev, "Using embedded (DMA) doorbell fallback\n");
+	return 0;
 }
 EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);
 
-- 
2.51.0

Re: [PATCH v8 8/9] PCI: endpoint: pci-epf-test: Reuse pre-exposed doorbell targets

[Niklas Cassel]

Hello Koichiro,

On Tue, Feb 17, 2026 at 05:06:00PM +0900, Koichiro Den wrote:
> pci-epf-test advertises the doorbell target to the RC as a BAR number
> and an offset, and the RC rings the doorbell with a single DWORD MMIO
> write.
> 
> Some doorbell backends may report that the doorbell target is already
> exposed via a platform-owned fixed BAR (db_msg[0].bar/offset). In that
> case, reuse the pre-exposed window and do not reprogram the BAR with
> pci_epc_set_bar().
> 
> Also honor db_msg[0].irq_flags when requesting the doorbell IRQ, and
> only restore the original BAR mapping on disable if pci-epf-test
> programmed it.
> 
> Reviewed-by: Frank Li <Frank.Li@nxp.com>
> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> ---

(snip)

> @@ -753,22 +771,33 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
>  	reg->doorbell_data = cpu_to_le32(msg->data);
>  	reg->doorbell_bar = cpu_to_le32(bar);
>  
> -	msg = &epf->db_msg[0].msg;
> -	ret = pci_epf_align_inbound_addr(epf, bar, ((u64)msg->address_hi << 32) | msg->address_lo,
> -					 &epf_test->db_bar.phys_addr, &offset);
> +	if (db->bar == NO_BAR) {
> +		ret = pci_epf_align_inbound_addr(epf, bar,
> +						 ((u64)msg->address_hi << 32) |
> +						 msg->address_lo,
> +						 &epf_test->db_bar.phys_addr,
> +						 &offset);
>  
> -	if (ret)
> -		goto err_free_irq;
> +		if (ret)
> +			goto err_free_irq;
> +	}

I tried this series on Rock5b (RK3588), and was surprised to see the doorbell
test case still failing.


> +
> +	if (size_add(offset, sizeof(u32)) > epf->bar[bar].size)
> +		goto err_doorbell_cleanup;

It turns out that this check is the reason for it still failing.

You see, for a BAR that is marked as BAR_RESERVED, pci-epf-test will not
allocate backing memory, so epf->bar[bar].size will be 0.

If I removed this check, I could get the test case to pass.

As I suggested in my previous email, perhaps this check is better suited
in pci_epf_alloc_doorbell(). (As a DWORD alignment check inside
pci_epf_alloc_doorbell(). pci_epf_alloc_doorbell() could itself return
error if the doorbell is not DWORD aligned.)

That way, you could remove this check from pci_epf_test_enable_doorbell(),
and we don't need to care about epf->bar[bar].size.


Kind regards,
Niklas

Re: [PATCH v8 3/9] PCI: endpoint: Add auxiliary resource query API

[Frank Li]

On Tue, Feb 17, 2026 at 05:05:55PM +0900, Koichiro Den wrote:
> Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
> engines) whose register windows and descriptor memories metadata need to
> be exposed to a remote peer. Endpoint function drivers need a generic
> way to discover such resources without hard-coding controller-specific
> helpers.
>
> Add pci_epc_get_aux_resources() and the corresponding pci_epc_ops
> get_aux_resources() callback. The API returns a list of resources
> described by type, physical address and size, plus type-specific
> metadata.
>
> Passing resources == NULL (or num_resources == 0) returns the required
> number of entries.
>
> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> ---
Reviewed-by: Frank Li <Frank.Li@nxp.com>
> Changes since v7:
>   - Add a 'data' field in pci_epc_aux_resource.u.db_mmio.
>   - Add comments describing the type-specific metadata fields.
>
>  drivers/pci/endpoint/pci-epc-core.c | 41 +++++++++++++++++++++++
>  include/linux/pci-epc.h             | 52 +++++++++++++++++++++++++++++
>  2 files changed, 93 insertions(+)
>
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index 068155819c57..01de4bd5047a 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -155,6 +155,47 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
>  }
>  EXPORT_SYMBOL_GPL(pci_epc_get_features);
>
> +/**
> + * pci_epc_get_aux_resources() - query EPC-provided auxiliary resources
> + * @epc: EPC device
> + * @func_no: function number
> + * @vfunc_no: virtual function number
> + * @resources: output array (may be NULL to query required count)
> + * @num_resources: size of @resources array in entries (0 when querying count)
> + *
> + * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
> + * registers and/or descriptor memories can be exposed to the host by mapping
> + * them into BAR space. This helper queries the backend for such resources.
> + *
> + * Return:
> + *   * >= 0: number of resources returned (or required, if @resources is NULL)
> + *   * -EOPNOTSUPP: backend does not support auxiliary resource queries
> + *   * other -errno on failure
> + */
> +int pci_epc_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> +			      struct pci_epc_aux_resource *resources,
> +			      int num_resources)
> +{
> +	int ret;
> +
> +	if (!epc || !epc->ops)
> +		return -EINVAL;
> +
> +	if (func_no >= epc->max_functions)
> +		return -EINVAL;
> +
> +	if (!epc->ops->get_aux_resources)
> +		return -EOPNOTSUPP;
> +
> +	mutex_lock(&epc->lock);
> +	ret = epc->ops->get_aux_resources(epc, func_no, vfunc_no, resources,
> +					  num_resources);
> +	mutex_unlock(&epc->lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(pci_epc_get_aux_resources);
> +
>  /**
>   * pci_epc_stop() - stop the PCI link
>   * @epc: the link of the EPC device that has to be stopped
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index 7a87f5962dd0..c68aaaf3542a 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -61,6 +61,51 @@ struct pci_epc_map {
>  	void __iomem	*virt_addr;
>  };
>
> +/**
> + * enum pci_epc_aux_resource_type - auxiliary resource type identifiers
> + * @PCI_EPC_AUX_DMA_CTRL_MMIO: Integrated DMA controller register window (MMIO)
> + * @PCI_EPC_AUX_DMA_CHAN_DESC: Per-channel DMA descriptor
> + * @PCI_EPC_AUX_DOORBELL_MMIO: Doorbell MMIO, that might be outside the DMA
> + *                             controller register window
> + *
> + * EPC backends may expose auxiliary blocks (e.g. DMA engines) by mapping their
> + * register windows and descriptor memories into BAR space. This enum
> + * identifies the type of each exposable resource.
> + */
> +enum pci_epc_aux_resource_type {
> +	PCI_EPC_AUX_DMA_CTRL_MMIO,
> +	PCI_EPC_AUX_DMA_CHAN_DESC,
> +	PCI_EPC_AUX_DOORBELL_MMIO,
> +};
> +
> +/**
> + * struct pci_epc_aux_resource - a physical auxiliary resource that may be
> + *                               exposed for peer use
> + * @type:       resource type, see enum pci_epc_aux_resource_type
> + * @phys_addr:  physical base address of the resource
> + * @size:       size of the resource in bytes
> + * @bar:        BAR number where this resource is already exposed to the RC
> + *              (NO_BAR if not)
> + * @bar_offset: offset within @bar where the resource starts (valid iff
> + *              @bar != NO_BAR)
> + * @u:          type-specific metadata
> + */
> +struct pci_epc_aux_resource {
> +	enum pci_epc_aux_resource_type type;
> +	phys_addr_t phys_addr;
> +	resource_size_t size;
> +	enum pci_barno bar;
> +	resource_size_t bar_offset;
> +
> +	union {
> +		/* PCI_EPC_AUX_DOORBELL_MMIO */
> +		struct {
> +			int irq; /* IRQ number for the doorbell handler */
> +			u32 data; /* write value to ring the doorbell */
> +		} db_mmio;
> +	} u;
> +};
> +
>  /**
>   * struct pci_epc_ops - set of function pointers for performing EPC operations
>   * @write_header: ops to populate configuration space header
> @@ -84,6 +129,7 @@ struct pci_epc_map {
>   * @start: ops to start the PCI link
>   * @stop: ops to stop the PCI link
>   * @get_features: ops to get the features supported by the EPC
> + * @get_aux_resources: ops to retrieve controller-owned auxiliary resources
>   * @owner: the module owner containing the ops
>   */
>  struct pci_epc_ops {
> @@ -115,6 +161,9 @@ struct pci_epc_ops {
>  	void	(*stop)(struct pci_epc *epc);
>  	const struct pci_epc_features* (*get_features)(struct pci_epc *epc,
>  						       u8 func_no, u8 vfunc_no);
> +	int	(*get_aux_resources)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> +				     struct pci_epc_aux_resource *resources,
> +				     int num_resources);
>  	struct module *owner;
>  };
>
> @@ -337,6 +386,9 @@ int pci_epc_start(struct pci_epc *epc);
>  void pci_epc_stop(struct pci_epc *epc);
>  const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
>  						    u8 func_no, u8 vfunc_no);
> +int pci_epc_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> +			      struct pci_epc_aux_resource *resources,
> +			      int num_resources);
>  enum pci_barno
>  pci_epc_get_first_free_bar(const struct pci_epc_features *epc_features);
>  enum pci_barno pci_epc_get_next_free_bar(const struct pci_epc_features
> --
> 2.51.0
>

Re: [PATCH v8 6/9] PCI: endpoint: pci-ep-msi: Refactor doorbell allocation for new backends

[Frank Li]

On Tue, Feb 17, 2026 at 05:05:58PM +0900, Koichiro Den wrote:
> Prepare pci-ep-msi for non-MSI doorbell backends.
>
> Factor MSI doorbell allocation into a helper and extend struct
> pci_epf_doorbell_msg with:
>
>   - irq_flags: required IRQ request flags (e.g. IRQF_SHARED for some
>     backends)
>   - type: doorbell backend type
>   - bar/offset: pre-exposed doorbell target location, if any
>
> Initialize these fields for the existing MSI-backed doorbell
> implementation.
>
> Also add PCI_EPF_DOORBELL_EMBEDDED type, which is to be implemented in a
> follow-up patch.
>
> No functional changes.
>
> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

> Changes since v7:
>   - Switch to designated initializer and rely on implicit
>     zero-initialization.
>
>  drivers/pci/endpoint/pci-ep-msi.c | 54 ++++++++++++++++++++++---------
>  include/linux/pci-epf.h           | 23 +++++++++++--
>  2 files changed, 60 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/pci/endpoint/pci-ep-msi.c b/drivers/pci/endpoint/pci-ep-msi.c
> index ad8a81d6ad77..50badffa9d72 100644
> --- a/drivers/pci/endpoint/pci-ep-msi.c
> +++ b/drivers/pci/endpoint/pci-ep-msi.c
> @@ -8,6 +8,7 @@
>
>  #include <linux/device.h>
>  #include <linux/export.h>
> +#include <linux/interrupt.h>
>  #include <linux/irqdomain.h>
>  #include <linux/module.h>
>  #include <linux/msi.h>
> @@ -35,23 +36,13 @@ static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
>  	pci_epc_put(epc);
>  }
>
> -int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
> +static int pci_epf_alloc_doorbell_msi(struct pci_epf *epf, u16 num_db)
>  {
> -	struct pci_epc *epc = epf->epc;
> +	struct pci_epf_doorbell_msg *msg;
>  	struct device *dev = &epf->dev;
> +	struct pci_epc *epc = epf->epc;
>  	struct irq_domain *domain;
> -	void *msg;
> -	int ret;
> -	int i;
> -
> -	/* TODO: Multi-EPF support */
> -	if (list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list) != epf) {
> -		dev_err(dev, "MSI doorbell doesn't support multiple EPF\n");
> -		return -EINVAL;
> -	}
> -
> -	if (epf->db_msg)
> -		return -EBUSY;
> +	int ret, i;
>
>  	domain = of_msi_map_get_device_domain(epc->dev.parent, 0,
>  					      DOMAIN_BUS_PLATFORM_MSI);
> @@ -74,6 +65,12 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
>  	if (!msg)
>  		return -ENOMEM;
>
> +	for (i = 0; i < num_db; i++)
> +		msg[i] = (struct pci_epf_doorbell_msg) {
> +			.type = PCI_EPF_DOORBELL_MSI,
> +			.bar = NO_BAR,
> +		};
> +
>  	epf->num_db = num_db;
>  	epf->db_msg = msg;
>
> @@ -90,13 +87,40 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
>  	for (i = 0; i < num_db; i++)
>  		epf->db_msg[i].virq = msi_get_virq(epc->dev.parent, i);
>
> +	return 0;
> +}
> +
> +int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
> +{
> +	struct pci_epc *epc = epf->epc;
> +	struct device *dev = &epf->dev;
> +	int ret;
> +
> +	/* TODO: Multi-EPF support */
> +	if (list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list) != epf) {
> +		dev_err(dev, "Doorbell doesn't support multiple EPF\n");
> +		return -EINVAL;
> +	}
> +
> +	if (epf->db_msg)
> +		return -EBUSY;
> +
> +	ret = pci_epf_alloc_doorbell_msi(epf, num_db);
> +	if (!ret)
> +		return 0;
> +
> +	dev_err(dev, "Failed to allocate doorbell: %d\n", ret);
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);
>
>  void pci_epf_free_doorbell(struct pci_epf *epf)
>  {
> -	platform_device_msi_free_irqs_all(epf->epc->dev.parent);
> +	if (!epf->db_msg)
> +		return;
> +
> +	if (epf->db_msg[0].type == PCI_EPF_DOORBELL_MSI)
> +		platform_device_msi_free_irqs_all(epf->epc->dev.parent);
>
>  	kfree(epf->db_msg);
>  	epf->db_msg = NULL;
> diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
> index 7737a7c03260..cd747447a1ea 100644
> --- a/include/linux/pci-epf.h
> +++ b/include/linux/pci-epf.h
> @@ -152,14 +152,33 @@ struct pci_epf_bar {
>  	struct pci_epf_bar_submap	*submap;
>  };
>
> +enum pci_epf_doorbell_type {
> +	PCI_EPF_DOORBELL_MSI = 0,
> +	PCI_EPF_DOORBELL_EMBEDDED,
> +};
> +
>  /**
>   * struct pci_epf_doorbell_msg - represents doorbell message
> - * @msg: MSI message
> - * @virq: IRQ number of this doorbell MSI message
> + * @msg: Doorbell address/data pair to be mapped into BAR space.
> + *       For MSI-backed doorbells this is the MSI message, while for
> + *       "embedded" doorbells this represents an MMIO write that asserts
> + *       an interrupt on the EP side.
> + * @virq: IRQ number of this doorbell message
> + * @irq_flags: Required flags for request_irq()/request_threaded_irq().
> + *             Callers may OR-in additional flags (e.g. IRQF_ONESHOT).
> + * @type: Doorbell type.
> + * @bar: BAR number where the doorbell target is already exposed to the RC
> + *       (NO_BAR if not)
> + * @offset: offset within @bar for the doorbell target (valid iff
> + *          @bar != NO_BAR)
>   */
>  struct pci_epf_doorbell_msg {
>  	struct msi_msg msg;
>  	int virq;
> +	unsigned long irq_flags;
> +	enum pci_epf_doorbell_type type;
> +	enum pci_barno bar;
> +	resource_size_t offset;
>  };
>
>  /**
> --
> 2.51.0
>

Re: [PATCH v8 9/9] PCI: endpoint: pci-ep-msi: Add embedded eDMA doorbell fallback

[Frank Li]

On Tue, Feb 17, 2026 at 05:06:01PM +0900, Koichiro Den wrote:
> Some endpoint platforms cannot use platform MSI / GIC ITS to implement
> EP-side doorbells. In those cases, EPF drivers cannot provide an
> interrupt-driven doorbell and often fall back to polling.
>
> Add an "embedded" doorbell backend that uses a controller-integrated
> doorbell target (e.g. DesignWare integrated eDMA interrupt-emulation
> doorbell).
>
> The backend locates the doorbell register and a corresponding Linux IRQ
> via the EPC aux-resource API. If the doorbell register is already
> exposed via a fixed BAR mapping, provide BAR+offset. Otherwise provide
> the physical address so EPF drivers can map it into BAR space.
>
> When MSI doorbell allocation fails with -ENODEV,
> pci_epf_alloc_doorbell() falls back to this embedded backend.
>
> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> ---
Reviewed-by: Frank Li <Frank.Li@nxp.com>

> Changes since v7:
>   - Use designated initializer for consistent styling.
>   - Clean up the pci_epf_alloc_doorbell() error path.
>
>  drivers/pci/endpoint/pci-ep-msi.c | 96 ++++++++++++++++++++++++++++++-
>  1 file changed, 94 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/endpoint/pci-ep-msi.c b/drivers/pci/endpoint/pci-ep-msi.c
> index 50badffa9d72..66f5a68c81b0 100644
> --- a/drivers/pci/endpoint/pci-ep-msi.c
> +++ b/drivers/pci/endpoint/pci-ep-msi.c
> @@ -6,6 +6,7 @@
>   * Author: Frank Li <Frank.Li@nxp.com>
>   */
>
> +#include <linux/cleanup.h>
>  #include <linux/device.h>
>  #include <linux/export.h>
>  #include <linux/interrupt.h>
> @@ -36,6 +37,84 @@ static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
>  	pci_epc_put(epc);
>  }
>
> +static int pci_epf_alloc_doorbell_embedded(struct pci_epf *epf, u16 num_db)
> +{
> +	const struct pci_epc_aux_resource *doorbell = NULL;
> +	struct pci_epf_doorbell_msg *msg;
> +	struct pci_epc *epc = epf->epc;
> +	struct device *dev = &epf->dev;
> +	int count, ret, i;
> +	u64 addr;
> +
> +	count = pci_epc_get_aux_resources(epc, epf->func_no, epf->vfunc_no,
> +					  NULL, 0);
> +	if (count == -EOPNOTSUPP || count == 0)
> +		return -ENODEV;
> +	if (count < 0)
> +		return count;
> +
> +	struct pci_epc_aux_resource *res __free(kfree) =
> +				kcalloc(count, sizeof(*res), GFP_KERNEL);
> +	if (!res)
> +		return -ENOMEM;
> +
> +	ret = pci_epc_get_aux_resources(epc, epf->func_no, epf->vfunc_no,
> +					res, count);
> +	if (ret == -EOPNOTSUPP || ret == 0)
> +		return -ENODEV;
> +	if (ret < 0)
> +		return ret;
> +
> +	count = ret;
> +
> +	for (i = 0; i < count; i++) {
> +		if (res[i].type == PCI_EPC_AUX_DOORBELL_MMIO) {
> +			if (doorbell) {
> +				dev_warn(dev,
> +					 "Duplicate DOORBELL_MMIO resource found\n");
> +				continue;
> +			}
> +			doorbell = &res[i];
> +		}
> +	}
> +	if (!doorbell)
> +		return -ENODEV;
> +
> +	msg = kcalloc(num_db, sizeof(*msg), GFP_KERNEL);
> +	if (!msg)
> +		return -ENOMEM;
> +
> +	addr = doorbell->phys_addr;
> +
> +	/*
> +	 * Embedded doorbell backends (e.g. DesignWare eDMA interrupt emulation)
> +	 * typically provide a single IRQ and do not offer per-doorbell
> +	 * distinguishable address/data pairs. The EPC aux resource therefore
> +	 * exposes one DOORBELL_MMIO entry (u.db_mmio.irq).
> +	 *
> +	 * Still, pci_epf_alloc_doorbell() allows requesting multiple doorbells.
> +	 * For such backends we replicate the same address/data for each entry
> +	 * and mark the IRQ as shared (IRQF_SHARED). Consumers must treat them
> +	 * as equivalent "kick" doorbells.
> +	 */
> +	for (i = 0; i < num_db; i++)
> +		msg[i] = (struct pci_epf_doorbell_msg) {
> +			.msg.address_lo = (u32)addr,
> +			.msg.address_hi = (u32)(addr >> 32),
> +			.msg.data = doorbell->u.db_mmio.data,
> +			.virq = doorbell->u.db_mmio.irq,
> +			.irq_flags = IRQF_SHARED,
> +			.type = PCI_EPF_DOORBELL_EMBEDDED,
> +			.bar = doorbell->bar,
> +			.offset = (doorbell->bar == NO_BAR) ? 0 :
> +				  doorbell->bar_offset,
> +		};
> +
> +	epf->num_db = num_db;
> +	epf->db_msg = msg;
> +	return 0;
> +}
> +
>  static int pci_epf_alloc_doorbell_msi(struct pci_epf *epf, u16 num_db)
>  {
>  	struct pci_epf_doorbell_msg *msg;
> @@ -109,8 +188,21 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
>  	if (!ret)
>  		return 0;
>
> -	dev_err(dev, "Failed to allocate doorbell: %d\n", ret);
> -	return ret;
> +	/*
> +	 * Fall back to embedded doorbell only when platform MSI is unavailable
> +	 * for this EPC.
> +	 */
> +	if (ret != -ENODEV)
> +		return ret;
> +
> +	ret = pci_epf_alloc_doorbell_embedded(epf, num_db);
> +	if (ret) {
> +		dev_err(dev, "Failed to allocate doorbell: %d\n", ret);
> +		return ret;
> +	}
> +
> +	dev_info(dev, "Using embedded (DMA) doorbell fallback\n");
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);
>
> --
> 2.51.0
>

Re: [PATCH v8 7/9] PCI: endpoint: pci-epf-vntb: Reuse pre-exposed doorbells and IRQ flags

[Frank Li]

On Tue, Feb 17, 2026 at 05:05:59PM +0900, Koichiro Den wrote:
> Support doorbell backends where the doorbell target is already exposed
> via a platform-owned fixed BAR mapping and/or where the doorbell IRQ
> must be requested with specific flags.
>
> When pci_epf_alloc_doorbell() provides db_msg[].bar/offset, reuse the
> pre-exposed BAR window and skip programming a new inbound mapping. Also
> honor db_msg[].irq_flags when requesting the doorbell IRQ.
>
> Multiple doorbells may share the same Linux IRQ. Avoid duplicate
> request_irq() calls by requesting each unique virq once.
>
> This makes pci-epf-vntb work with platform-defined or embedded doorbell

Nit: Make pci-epf-vntb work with ...

> backends without exposing backend-specific details to the consumer
> layer.
>
> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> ---
> Changes since v7:
>   - Deduplicate request_irq()/free_irq() calls based on virq (shared
>     IRQ) rather than doorbell type.
>
>  drivers/pci/endpoint/functions/pci-epf-vntb.c | 61 ++++++++++++++++++-
>  1 file changed, 58 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> index 52cf442ca1d9..b1e8414c4e43 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> @@ -134,6 +134,11 @@ struct epf_ntb {
>  	u16 vntb_vid;
>
>  	bool linkup;
> +
> +	/*
> +	 * True when doorbells are interrupt-driven (MSI or embedded), false
> +	 * when polled.
> +	 */
>  	bool msi_doorbell;
>  	u32 spad_size;
>
> @@ -517,6 +522,17 @@ static int epf_ntb_configure_interrupt(struct epf_ntb *ntb)
>  	return 0;
>  }
>
> +static bool epf_ntb_db_irq_is_first(const struct pci_epf *epf, unsigned int idx)

epf_ntb_db_irq_is_duplicated() look better, below 'if' needn't !

Frank

> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < idx; i++)
> +		if (epf->db_msg[i].virq == epf->db_msg[idx].virq)
> +			return false;
> +
> +	return true;
> +}
> +
>  static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
>  					    struct pci_epf_bar *db_bar,
>  					    const struct pci_epc_features *epc_features,
> @@ -533,9 +549,24 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
>  	if (ret)
>  		return ret;
>
> +	/*
> +	 * The doorbell target may already be exposed by a platform-owned fixed
> +	 * BAR. In that case, we must reuse it and the requested db_bar must
> +	 * match.
> +	 */
> +	if (epf->db_msg[0].bar != NO_BAR && epf->db_msg[0].bar != barno) {
> +		ret = -EINVAL;
> +		goto err_free_doorbell;
> +	}
> +
>  	for (req = 0; req < ntb->db_count; req++) {
> +		/* Avoid requesting duplicate handlers */
> +		if (!epf_ntb_db_irq_is_first(epf, req))
> +			continue;
> +
>  		ret = request_irq(epf->db_msg[req].virq, epf_ntb_doorbell_handler,
> -				  0, "pci_epf_vntb_db", ntb);
> +				  epf->db_msg[req].irq_flags, "pci_epf_vntb_db",
> +				  ntb);
>
>  		if (ret) {
>  			dev_err(&epf->dev,
> @@ -545,6 +576,22 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
>  		}
>  	}
>
> +	if (epf->db_msg[0].bar != NO_BAR) {
> +		for (i = 0; i < ntb->db_count; i++) {
> +			msg = &epf->db_msg[i].msg;
> +
> +			if (epf->db_msg[i].bar != barno) {
> +				ret = -EINVAL;
> +				goto err_free_irq;
> +			}
> +
> +			ntb->reg->db_data[i] = msg->data;
> +			ntb->reg->db_offset[i] = epf->db_msg[i].offset;
> +		}
> +		goto out;
> +	}
> +
> +	/* Program inbound mapping for the doorbell */
>  	msg = &epf->db_msg[0].msg;
>
>  	high = 0;
> @@ -591,6 +638,7 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
>  		ntb->reg->db_offset[i] = offset;
>  	}
>
> +out:
>  	ntb->reg->db_entry_size = 0;
>
>  	ntb->msi_doorbell = true;
> @@ -598,9 +646,13 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
>  	return 0;
>
>  err_free_irq:
> -	for (req--; req >= 0; req--)
> +	for (req--; req >= 0; req--) {
> +		if (!epf_ntb_db_irq_is_first(epf, req))
> +			continue;
>  		free_irq(epf->db_msg[req].virq, ntb);
> +	}
>
> +err_free_doorbell:
>  	pci_epf_free_doorbell(ntb->epf);
>  	return ret;
>  }
> @@ -666,8 +718,11 @@ static void epf_ntb_db_bar_clear(struct epf_ntb *ntb)
>  	if (ntb->msi_doorbell) {
>  		int i;
>
> -		for (i = 0; i < ntb->db_count; i++)
> +		for (i = 0; i < ntb->db_count; i++) {
> +			if (!epf_ntb_db_irq_is_first(ntb->epf, i))
> +				continue;
>  			free_irq(ntb->epf->db_msg[i].virq, ntb);
> +		}
>  	}
>
>  	if (ntb->epf->db_msg)
> --
> 2.51.0
>

Re: [PATCH v8 7/9] PCI: endpoint: pci-epf-vntb: Reuse pre-exposed doorbells and IRQ flags

[Koichiro Den]

On Tue, Feb 17, 2026 at 11:54:29AM -0500, Frank Li wrote:
> On Tue, Feb 17, 2026 at 05:05:59PM +0900, Koichiro Den wrote:
> > Support doorbell backends where the doorbell target is already exposed
> > via a platform-owned fixed BAR mapping and/or where the doorbell IRQ
> > must be requested with specific flags.
> >
> > When pci_epf_alloc_doorbell() provides db_msg[].bar/offset, reuse the
> > pre-exposed BAR window and skip programming a new inbound mapping. Also
> > honor db_msg[].irq_flags when requesting the doorbell IRQ.
> >
> > Multiple doorbells may share the same Linux IRQ. Avoid duplicate
> > request_irq() calls by requesting each unique virq once.
> >
> > This makes pci-epf-vntb work with platform-defined or embedded doorbell
> 
> Nit: Make pci-epf-vntb work with ...
> 
> > backends without exposing backend-specific details to the consumer
> > layer.
> >
> > Signed-off-by: Koichiro Den <den@valinux.co.jp>
> > ---
> > Changes since v7:
> >   - Deduplicate request_irq()/free_irq() calls based on virq (shared
> >     IRQ) rather than doorbell type.
> >
> >  drivers/pci/endpoint/functions/pci-epf-vntb.c | 61 ++++++++++++++++++-
> >  1 file changed, 58 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > index 52cf442ca1d9..b1e8414c4e43 100644
> > --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > @@ -134,6 +134,11 @@ struct epf_ntb {
> >  	u16 vntb_vid;
> >
> >  	bool linkup;
> > +
> > +	/*
> > +	 * True when doorbells are interrupt-driven (MSI or embedded), false
> > +	 * when polled.
> > +	 */
> >  	bool msi_doorbell;
> >  	u32 spad_size;
> >
> > @@ -517,6 +522,17 @@ static int epf_ntb_configure_interrupt(struct epf_ntb *ntb)
> >  	return 0;
> >  }
> >
> > +static bool epf_ntb_db_irq_is_first(const struct pci_epf *epf, unsigned int idx)
> 
> epf_ntb_db_irq_is_duplicated() look better, below 'if' needn't !

Agreed. I'll rename it and update the usage in the next revision.

Thanks for the review,
Koichiro

> 
> Frank
> 
> > +{
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < idx; i++)
> > +		if (epf->db_msg[i].virq == epf->db_msg[idx].virq)
> > +			return false;
> > +
> > +	return true;
> > +}
> > +
> >  static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
> >  					    struct pci_epf_bar *db_bar,
> >  					    const struct pci_epc_features *epc_features,
> > @@ -533,9 +549,24 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
> >  	if (ret)
> >  		return ret;
> >
> > +	/*
> > +	 * The doorbell target may already be exposed by a platform-owned fixed
> > +	 * BAR. In that case, we must reuse it and the requested db_bar must
> > +	 * match.
> > +	 */
> > +	if (epf->db_msg[0].bar != NO_BAR && epf->db_msg[0].bar != barno) {
> > +		ret = -EINVAL;
> > +		goto err_free_doorbell;
> > +	}
> > +
> >  	for (req = 0; req < ntb->db_count; req++) {
> > +		/* Avoid requesting duplicate handlers */
> > +		if (!epf_ntb_db_irq_is_first(epf, req))
> > +			continue;
> > +
> >  		ret = request_irq(epf->db_msg[req].virq, epf_ntb_doorbell_handler,
> > -				  0, "pci_epf_vntb_db", ntb);
> > +				  epf->db_msg[req].irq_flags, "pci_epf_vntb_db",
> > +				  ntb);
> >
> >  		if (ret) {
> >  			dev_err(&epf->dev,
> > @@ -545,6 +576,22 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
> >  		}
> >  	}
> >
> > +	if (epf->db_msg[0].bar != NO_BAR) {
> > +		for (i = 0; i < ntb->db_count; i++) {
> > +			msg = &epf->db_msg[i].msg;
> > +
> > +			if (epf->db_msg[i].bar != barno) {
> > +				ret = -EINVAL;
> > +				goto err_free_irq;
> > +			}
> > +
> > +			ntb->reg->db_data[i] = msg->data;
> > +			ntb->reg->db_offset[i] = epf->db_msg[i].offset;
> > +		}
> > +		goto out;
> > +	}
> > +
> > +	/* Program inbound mapping for the doorbell */
> >  	msg = &epf->db_msg[0].msg;
> >
> >  	high = 0;
> > @@ -591,6 +638,7 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
> >  		ntb->reg->db_offset[i] = offset;
> >  	}
> >
> > +out:
> >  	ntb->reg->db_entry_size = 0;
> >
> >  	ntb->msi_doorbell = true;
> > @@ -598,9 +646,13 @@ static int epf_ntb_db_bar_init_msi_doorbell(struct epf_ntb *ntb,
> >  	return 0;
> >
> >  err_free_irq:
> > -	for (req--; req >= 0; req--)
> > +	for (req--; req >= 0; req--) {
> > +		if (!epf_ntb_db_irq_is_first(epf, req))
> > +			continue;
> >  		free_irq(epf->db_msg[req].virq, ntb);
> > +	}
> >
> > +err_free_doorbell:
> >  	pci_epf_free_doorbell(ntb->epf);
> >  	return ret;
> >  }
> > @@ -666,8 +718,11 @@ static void epf_ntb_db_bar_clear(struct epf_ntb *ntb)
> >  	if (ntb->msi_doorbell) {
> >  		int i;
> >
> > -		for (i = 0; i < ntb->db_count; i++)
> > +		for (i = 0; i < ntb->db_count; i++) {
> > +			if (!epf_ntb_db_irq_is_first(ntb->epf, i))
> > +				continue;
> >  			free_irq(ntb->epf->db_msg[i].virq, ntb);
> > +		}
> >  	}
> >
> >  	if (ntb->epf->db_msg)
> > --
> > 2.51.0
> >

Re: [PATCH v8 8/9] PCI: endpoint: pci-epf-test: Reuse pre-exposed doorbell targets

[Koichiro Den]

On Tue, Feb 17, 2026 at 11:15:08AM +0100, Niklas Cassel wrote:
> Hello Koichiro,
> 
> On Tue, Feb 17, 2026 at 05:06:00PM +0900, Koichiro Den wrote:
> > pci-epf-test advertises the doorbell target to the RC as a BAR number
> > and an offset, and the RC rings the doorbell with a single DWORD MMIO
> > write.
> > 
> > Some doorbell backends may report that the doorbell target is already
> > exposed via a platform-owned fixed BAR (db_msg[0].bar/offset). In that
> > case, reuse the pre-exposed window and do not reprogram the BAR with
> > pci_epc_set_bar().
> > 
> > Also honor db_msg[0].irq_flags when requesting the doorbell IRQ, and
> > only restore the original BAR mapping on disable if pci-epf-test
> > programmed it.
> > 
> > Reviewed-by: Frank Li <Frank.Li@nxp.com>
> > Signed-off-by: Koichiro Den <den@valinux.co.jp>
> > ---
> 
> (snip)
> 
> > @@ -753,22 +771,33 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
> >  	reg->doorbell_data = cpu_to_le32(msg->data);
> >  	reg->doorbell_bar = cpu_to_le32(bar);
> >  
> > -	msg = &epf->db_msg[0].msg;
> > -	ret = pci_epf_align_inbound_addr(epf, bar, ((u64)msg->address_hi << 32) | msg->address_lo,
> > -					 &epf_test->db_bar.phys_addr, &offset);
> > +	if (db->bar == NO_BAR) {
> > +		ret = pci_epf_align_inbound_addr(epf, bar,
> > +						 ((u64)msg->address_hi << 32) |
> > +						 msg->address_lo,
> > +						 &epf_test->db_bar.phys_addr,
> > +						 &offset);
> >  
> > -	if (ret)
> > -		goto err_free_irq;
> > +		if (ret)
> > +			goto err_free_irq;
> > +	}
> 
> I tried this series on Rock5b (RK3588), and was surprised to see the doorbell
> test case still failing.

Thank you very much for testing, and apologies for not being able to test on
RK3588 on my side right now.

> 
> 
> > +
> > +	if (size_add(offset, sizeof(u32)) > epf->bar[bar].size)
> > +		goto err_doorbell_cleanup;
> 
> It turns out that this check is the reason for it still failing.
> 
> You see, for a BAR that is marked as BAR_RESERVED, pci-epf-test will not
> allocate backing memory, so epf->bar[bar].size will be 0.
> 
> If I removed this check, I could get the test case to pass.
> 
> As I suggested in my previous email, perhaps this check is better suited
> in pci_epf_alloc_doorbell(). (As a DWORD alignment check inside
> pci_epf_alloc_doorbell(). pci_epf_alloc_doorbell() could itself return
> error if the doorbell is not DWORD aligned.)

Yes, and I mentioned there I would reconsider this when respinning this feature
series. For reference:
https://lore.kernel.org/linux-pci/jcjson6zedvhkpctwzfao2wfaaujtdfqsnnm3k25e2vpz2evf4@hbsegnyevisu/
I hadn't noticed the bar.size==0 possibility at that time.

I agree that this check is better placed in pci_epf_alloc_doorbell().
I'll respin accordingly.

Thanks again for the testing and review,
Koichiro

> 
> That way, you could remove this check from pci_epf_test_enable_doorbell(),
> and we don't need to care about epf->bar[bar].size.
> 
> 
> Kind regards,
> Niklas