[PATCH v4 2/4] PCI: dwc: Add ECAM support with iATU configuration

Krishna Chaitanya Chundru
2025-02-06T23:29:19Z

The current implementation requires iATU for every configuration
space access which increases latency & cpu utilization.

Designware databook 5.20a, section 3.10.10.3 says about CFG Shift Feature,
which shifts/maps the BDF (bits [31:16] of the third header DWORD, which
would be matched against the Base and Limit addresses) of the incoming
CfgRd0/CfgWr0 down to bits[27:12]of the translated address.

Configuring iATU in config shift feature enables ECAM feature to access the
config space, which avoids iATU configuration for every config access.

Add "ctrl2" into struct dw_pcie_ob_atu_cfg to enable config shift feature.

As DBI comes under config space, this avoids remapping of DBI space
separately. Instead, it uses the mapped config space address returned from
ECAM initialization. Change the order of dw_pcie_get_resources() execution
to achieve this.

Enable the ECAM feature if the config space size is equal to size required
to represent number of buses in the bus range property, add a function
which checks this. The DWC glue drivers uses this function and decide to
enable ECAM mode or not.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
drivers/pci/controller/dwc/Kconfig | 1 +
drivers/pci/controller/dwc/pcie-designware-host.c | 133 +++++++++++++++++++---
drivers/pci/controller/dwc/pcie-designware.c | 2 +-
drivers/pci/controller/dwc/pcie-designware.h | 11 ++
4 files changed, 132 insertions(+), 15 deletions(-)

diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
index b6d6778b0698..73c3aed6b60a 100644
--- a/drivers/pci/controller/dwc/Kconfig
+++ b/drivers/pci/controller/dwc/Kconfig
@@ -9,6 +9,7 @@ config PCIE_DW
config PCIE_DW_HOST
bool
select PCIE_DW
+ select PCI_HOST_COMMON

config PCIE_DW_EP
bool
diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index ffaded8f2df7..826ff9338646 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -418,6 +418,66 @@ static void dw_pcie_host_request_msg_tlp_res(struct dw_pcie_rp *pp)
}
}

+static int dw_pcie_config_ecam_iatu(struct dw_pcie_rp *pp)
+{
+ struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+ struct dw_pcie_ob_atu_cfg atu = {0};
+ resource_size_t bus_range_max;
+ struct resource_entry *bus;
+ int ret;
+
+ bus = resource_list_first_type(&pp->bridge->windows, IORESOURCE_BUS);
+
+ /*
+ * Root bus under the host bridge doesn't require any iATU configuration
+ * as DBI space will represent Root bus configuration space.
+ * Immediate bus under Root Bus, needs type 0 iATU configuration and
+ * remaining buses need type 1 iATU configuration.
+ */
+ atu.index = 0;
+ atu.type = PCIE_ATU_TYPE_CFG0;
+ atu.cpu_addr = pp->cfg0_base + SZ_1M;
+ atu.size = SZ_1M;
+ atu.ctrl2 = PCIE_ATU_CFG_SHIFT_MODE_ENABLE;
+ ret = dw_pcie_prog_outbound_atu(pci, &atu);
+ if (ret)
+ return ret;
+
+ bus_range_max = resource_size(bus->res);
+
+ if (bus_range_max < 2)
+ return 0;
+
+ /* Configure remaining buses in type 1 iATU configuration */
+ atu.index = 1;
+ atu.type = PCIE_ATU_TYPE_CFG1;
+ atu.cpu_addr = pp->cfg0_base + SZ_2M;
+ atu.size = (SZ_1M * (bus_range_max - 2));
+ atu.ctrl2 = PCIE_ATU_CFG_SHIFT_MODE_ENABLE;
+
+ return dw_pcie_prog_outbound_atu(pci, &atu);
+}
+
+static int dw_pcie_create_ecam_window(struct dw_pcie_rp *pp, struct resource *res)
+{
+ struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+ struct device *dev = pci->dev;
+ struct resource_entry *bus;
+
+ bus = resource_list_first_type(&pp->bridge->windows, IORESOURCE_BUS);
+ if (!bus)
+ return -ENODEV;
+
+ pp->cfg = pci_ecam_create(dev, res, bus->res, &pci_generic_ecam_ops);
+ if (IS_ERR(pp->cfg))
+ return PTR_ERR(pp->cfg);
+
+ pci->dbi_base = pp->cfg->win;
+ pci->dbi_phys_addr = res->start;
+
+ return 0;
+}
+
int dw_pcie_host_init(struct dw_pcie_rp *pp)
{
struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
@@ -431,10 +491,6 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)

raw_spin_lock_init(&pp->lock);

- ret = dw_pcie_get_resources(pci);
- if (ret)
- return ret;
-
res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "config");
if (!res) {
dev_err(dev, "Missing \"config\" reg space\n");
@@ -444,9 +500,28 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
pp->cfg0_size = resource_size(res);
pp->cfg0_base = res->start;

- pp->va_cfg0_base = devm_pci_remap_cfg_resource(dev, res);
- if (IS_ERR(pp->va_cfg0_base))
- return PTR_ERR(pp->va_cfg0_base);
+ if (pp->ecam_mode) {
+ ret = dw_pcie_create_ecam_window(pp, res);
+ if (ret)
+ return ret;
+
+ bridge->ops = (struct pci_ops *)&pci_generic_ecam_ops.pci_ops;
+ pp->bridge->sysdata = pp->cfg;
+ pp->cfg->priv = pp;
+ } else {
+ pp->va_cfg0_base = devm_pci_remap_cfg_resource(dev, res);
+ if (IS_ERR(pp->va_cfg0_base))
+ return PTR_ERR(pp->va_cfg0_base);
+
+ /* Set default bus ops */
+ bridge->ops = &dw_pcie_ops;
+ bridge->child_ops = &dw_child_pcie_ops;
+ bridge->sysdata = pp;
+ }
+
+ ret = dw_pcie_get_resources(pci);
+ if (ret)
+ return ret;

bridge = devm_pci_alloc_host_bridge(dev, 0);
if (!bridge)
@@ -462,14 +537,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
pp->io_base = pci_pio_to_address(win->res->start);
}

- /* Set default bus ops */
- bridge->ops = &dw_pcie_ops;
- bridge->child_ops = &dw_child_pcie_ops;
-
if (pp->ops->init) {
ret = pp->ops->init(pp);
if (ret)
- return ret;
+ goto err_free_ecam;
}

if (pci_msi_enabled()) {
@@ -504,6 +575,14 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)

dw_pcie_iatu_detect(pci);

+ if (pp->ecam_mode) {
+ ret = dw_pcie_config_ecam_iatu(pp);
+ if (ret) {
+ dev_err(dev, "Failed to confuure iATU\n");
+ goto err_free_msi;
+ }
+ }
+
/*
* Allocate the resource for MSG TLP before programming the iATU
* outbound window in dw_pcie_setup_rc(). Since the allocation depends
@@ -539,8 +618,6 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
/* Ignore errors, the link may come up later */
dw_pcie_wait_for_link(pci);

- bridge->sysdata = pp;
-
ret = pci_host_probe(bridge);
if (ret)
goto err_stop_link;
@@ -564,6 +641,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
if (pp->ops->deinit)
pp->ops->deinit(pp);

+err_free_ecam:
+ if (pp->cfg)
+ pci_ecam_free(pp->cfg);
+
return ret;
}
EXPORT_SYMBOL_GPL(dw_pcie_host_init);
@@ -584,6 +665,9 @@ void dw_pcie_host_deinit(struct dw_pcie_rp *pp)

if (pp->ops->deinit)
pp->ops->deinit(pp);
+
+ if (pp->cfg)
+ pci_ecam_free(pp->cfg);
}
EXPORT_SYMBOL_GPL(dw_pcie_host_deinit);

@@ -999,3 +1083,24 @@ int dw_pcie_resume_noirq(struct dw_pcie *pci)
return ret;
}
EXPORT_SYMBOL_GPL(dw_pcie_resume_noirq);
+
+bool dw_pcie_ecam_supported(struct dw_pcie_rp *pp)
+{
+ struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+ struct platform_device *pdev = to_platform_device(pci->dev);
+ struct resource *config_res, *bus_range;
+ u64 bus_config_space_count;
+
+ bus_range = resource_list_first_type(&pp->bridge->windows, IORESOURCE_BUS)->res;
+ if (!bus_range)
+ return false;
+
+ config_res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "config");
+ if (!config_res)
+ return false;
+
+ bus_config_space_count = resource_size(config_res) >> PCIE_ECAM_BUS_SHIFT;
+
+ return !!(bus_config_space_count >= resource_size(bus_range));
+}
+EXPORT_SYMBOL_GPL(dw_pcie_ecam_supported);
diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 145e7f579072..523ca7f267fb 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -509,7 +509,7 @@ int dw_pcie_prog_outbound_atu(struct dw_pcie *pci,
val = dw_pcie_enable_ecrc(val);
dw_pcie_writel_atu_ob(pci, atu->index, PCIE_ATU_REGION_CTRL1, val);

- val = PCIE_ATU_ENABLE;
+ val = PCIE_ATU_ENABLE | atu->ctrl2;
if (atu->type == PCIE_ATU_TYPE_MSG) {
/* The data-less messages only for now */
val |= PCIE_ATU_INHIBIT_PAYLOAD | atu->code;
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 501d9ddfea16..d0ba8855ba2a 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -20,6 +20,7 @@
#include <linux/irq.h>
#include <linux/msi.h>
#include <linux/pci.h>
+#include <linux/pci-ecam.h>
#include <linux/reset.h>

#include <linux/pci-epc.h>
@@ -171,6 +172,7 @@
#define PCIE_ATU_REGION_CTRL2 0x004
#define PCIE_ATU_ENABLE BIT(31)
#define PCIE_ATU_BAR_MODE_ENABLE BIT(30)
+#define PCIE_ATU_CFG_SHIFT_MODE_ENABLE BIT(28)
#define PCIE_ATU_INHIBIT_PAYLOAD BIT(22)
#define PCIE_ATU_FUNC_NUM_MATCH_EN BIT(19)
#define PCIE_ATU_LOWER_BASE 0x008
@@ -343,6 +345,7 @@ struct dw_pcie_ob_atu_cfg {
u8 func_no;
u8 code;
u8 routing;
+ u32 ctrl2;
u64 cpu_addr;
u64 pci_addr;
u64 size;
@@ -381,6 +384,8 @@ struct dw_pcie_rp {
int msg_atu_index;
struct resource *msg_res;
bool use_linkup_irq;
+ bool ecam_mode;
+ struct pci_config_window *cfg;
};

struct dw_pcie_ep_ops {
@@ -686,6 +691,7 @@ void dw_pcie_host_deinit(struct dw_pcie_rp *pp);
int dw_pcie_allocate_domains(struct dw_pcie_rp *pp);
void __iomem *dw_pcie_own_conf_map_bus(struct pci_bus *bus, unsigned int devfn,
int where);
+bool dw_pcie_ecam_supported(struct dw_pcie_rp *pp);
#else
static inline int dw_pcie_suspend_noirq(struct dw_pcie *pci)
{
@@ -726,6 +732,11 @@ static inline void __iomem *dw_pcie_own_conf_map_bus(struct pci_bus *bus,
{
return NULL;
}
+
+static inline bool dw_pcie_ecam_supported(struct dw_pcie_rp *pp)
+{
+ return 0;
+}
#endif

#ifdef CONFIG_PCIE_DW_EP

--
2.34.1