[PATCH v6 4/4] pcie: endpoint: pci-epf-vntb: add endpoint MSI support

Frank Li
2022-08-18T15:20:22Z

┌───────┐ ┌──────────┐
│ │ │ │
┌─────────────┐ │ │ │ PCI Host │
│ MSI │◄┐ │ │ │ │
│ Controller │ │ │ │ │ │
└─────────────┘ └─┼───────┼──────────┼─BAR0 │
│ PCI │ │ BAR1 │
│ Func │ │ BAR2 │
│ │ │ BAR3 │
│ │ │ BAR4 │
│ ├─────────►│ │
└───────┘ └──────────┘

Linux supports endpoint functions. PCI Host write BAR<n> space like write
to memory. The EP side can't know memory changed by the host driver.

PCI Spec has not defined a standard method to do that. Only define MSI(x)
to let EP notified RC status change.

The basic idea is to trigger an IRQ when PCI RC writes to a memory
address. That's what MSI controller provided. EP drivers just need to
request a platform MSI interrupt, struct msi_msg *msg will pass down a
memory address and data. EP driver will map such memory address to one of
PCI BAR<n>. Host just writes such an address to trigger EP side irq.

Add MSI support for pci-epf-vntb. pci-epf-vntb driver query if system
have MSI controller. Setup doorbell address according to struct msi_msg.

So PCIe host can write this doorbell address to triger EP side's irq.

If no MSI controller exist, fall back to software polling.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
drivers/pci/endpoint/functions/pci-epf-vntb.c | 134 +++++++++++++++---
1 file changed, 112 insertions(+), 22 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index 1466dd1904175..ad4f7ec8a39fc 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -44,6 +44,7 @@
#include <linux/pci-epc.h>
#include <linux/pci-epf.h>
#include <linux/ntb.h>
+#include <linux/msi.h>

static struct workqueue_struct *kpcintb_workqueue;

@@ -143,6 +144,8 @@ struct epf_ntb {
void __iomem *vpci_mw_addr[MAX_MW];

struct delayed_work cmd_handler;
+
+ int msi_virqbase;
};

#define to_epf_ntb(epf_group) container_of((epf_group), struct epf_ntb, group)
@@ -253,7 +256,7 @@ static void epf_ntb_cmd_handler(struct work_struct *work)

ntb = container_of(work, struct epf_ntb, cmd_handler.work);

- for (i = 1; i < ntb->db_count; i++) {
+ for (i = 1; i < ntb->db_count && !ntb->epf_db_phy; i++) {
if (readl(ntb->epf_db + i * 4)) {
if (readl(ntb->epf_db + i * 4))
ntb->db |= 1 << (i - 1);
@@ -454,11 +457,9 @@ static int epf_ntb_config_spad_bar_alloc(struct epf_ntb *ntb)
ctrl->num_mws = ntb->num_mws;
ntb->spad_size = spad_size;

- ctrl->db_entry_size = 4;
-
for (i = 0; i < ntb->db_count; i++) {
ntb->reg->db_data[i] = 1 + i;
- ntb->reg->db_offset[i] = 0;
+ ntb->reg->db_offset[i] = 4 * i;
}

return 0;
@@ -509,6 +510,28 @@ static int epf_ntb_configure_interrupt(struct epf_ntb *ntb)
return 0;
}

+static int epf_ntb_db_size(struct epf_ntb *ntb)
+{
+ const struct pci_epc_features *epc_features;
+ size_t size = 4 * ntb->db_count;
+ u32 align;
+
+ epc_features = pci_epc_get_features(ntb->epf->epc,
+ ntb->epf->func_no,
+ ntb->epf->vfunc_no);
+ align = epc_features->align;
+
+ if (size < 128)
+ size = 128;
+
+ if (align)
+ size = ALIGN(size, align);
+ else
+ size = roundup_pow_of_two(size);
+
+ return size;
+}
+
/**
* epf_ntb_db_bar_init() - Configure Doorbell window BARs
* @ntb: NTB device that facilitates communication between HOST and vHOST
@@ -520,35 +543,33 @@ static int epf_ntb_db_bar_init(struct epf_ntb *ntb)
struct device *dev = &ntb->epf->dev;
int ret;
struct pci_epf_bar *epf_bar;
- void __iomem *mw_addr;
+ void __iomem *mw_addr = NULL;
enum pci_barno barno;
- size_t size = 4 * ntb->db_count;
+ size_t size;

epc_features = pci_epc_get_features(ntb->epf->epc,
ntb->epf->func_no,
ntb->epf->vfunc_no);
align = epc_features->align;
-
- if (size < 128)
- size = 128;
-
- if (align)
- size = ALIGN(size, align);
- else
- size = roundup_pow_of_two(size);
+ size = epf_ntb_db_size(ntb);

barno = ntb->epf_ntb_bar[BAR_DB];
+ epf_bar = &ntb->epf->bar[barno];

- mw_addr = pci_epf_alloc_space(ntb->epf, size, barno, align, 0);
- if (!mw_addr) {
- dev_err(dev, "Failed to allocate OB address\n");
- return -ENOMEM;
+ if (!ntb->epf_db_phy) {
+ mw_addr = pci_epf_alloc_space(ntb->epf, size, barno, align, 0);
+ if (!mw_addr) {
+ dev_err(dev, "Failed to allocate OB address\n");
+ return -ENOMEM;
+ }
+ } else {
+ epf_bar->phys_addr = ntb->epf_db_phy;
+ epf_bar->barno = barno;
+ epf_bar->size = size;
}

ntb->epf_db = mw_addr;

- epf_bar = &ntb->epf->bar[barno];
-
ret = pci_epc_set_bar(ntb->epf->epc, ntb->epf->func_no, ntb->epf->vfunc_no, epf_bar);
if (ret) {
dev_err(dev, "Doorbell BAR set failed\n");
@@ -704,6 +725,74 @@ static int epf_ntb_init_epc_bar(struct epf_ntb *ntb)
return 0;
}

+static void epf_ntb_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
+{
+ struct epf_ntb *ntb = dev_get_drvdata(desc->dev);
+ struct epf_ntb_ctrl *reg = ntb->reg;
+ int size = epf_ntb_db_size(ntb);
+ u64 addr;
+
+ addr = msg->address_hi;
+ addr <<= 32;
+ addr |= msg->address_lo;
+
+ reg->db_data[desc->msi_index] = msg->data;
+
+ if (desc->msi_index == 0)
+ ntb->epf_db_phy = round_down(addr, size);
+
+ reg->db_offset[desc->msi_index] = addr - ntb->epf_db_phy;
+}
+
+static irqreturn_t epf_ntb_interrupt_handler(int irq, void *data)
+{
+ struct epf_ntb *ntb = data;
+ int index;
+
+ index = irq - ntb->msi_virqbase;
+ ntb->db |= 1 << (index - 1);
+ ntb_db_event(&ntb->ntb, index);
+
+ return IRQ_HANDLED;
+}
+
+static void epf_ntb_epc_msi_init(struct epf_ntb *ntb)
+{
+ struct device *dev = &ntb->epf->dev;
+ struct irq_domain *domain;
+ int virq;
+ int ret;
+ int i;
+
+ domain = dev_get_msi_domain(ntb->epf->epc->dev.parent);
+ if (!domain)
+ return;
+
+ dev_set_msi_domain(dev, domain);
+
+ if (platform_msi_domain_alloc_irqs(&ntb->epf->dev,
+ ntb->db_count,
+ epf_ntb_write_msi_msg)) {
+ dev_info(dev, "Can't allocate MSI, fall back to poll mode\n");
+ return;
+ }
+
+ dev_info(dev, "vntb use MSI as doorbell\n");
+
+ for (i = 0; i < ntb->db_count; i++) {
+ virq = msi_get_virq(dev, i);
+ ret = devm_request_irq(dev, virq,
+ epf_ntb_interrupt_handler, 0,
+ "ntb", ntb);
+
+ if (ret)
+ dev_err(dev, "devm_request_irq() failure\n");
+
+ if (!i)
+ ntb->msi_virqbase = virq;
+ }
+}
+
/**
* epf_ntb_epc_init() - Initialize NTB interface
* @ntb: NTB device that facilitates communication between HOST and vHOST2
@@ -1299,14 +1388,15 @@ static int epf_ntb_bind(struct pci_epf *epf)
goto err_bar_alloc;
}

+ epf_set_drvdata(epf, ntb);
+ epf_ntb_epc_msi_init(ntb);
+
ret = epf_ntb_epc_init(ntb);
if (ret) {
dev_err(dev, "Failed to initialize EPC\n");
goto err_bar_alloc;
}

- epf_set_drvdata(epf, ntb);
-
pci_space[0] = (ntb->vntb_pid << 16) | ntb->vntb_vid;
pci_vntb_table[0].vendor = ntb->vntb_vid;
pci_vntb_table[0].device = ntb->vntb_pid;
--
2.35.1