[PATCH 09/13] PCI: aardvark: Implement re-issuing config requests on CRS response

Marek Behún
2021-10-01T19:59:17Z

From: Pali Rohár <pali@kernel.org>

Commit 43f5c77bcbd2 ("PCI: aardvark: Fix reporting CRS value") fixed
handling of CRS response and when CRSSVE flag was not enabled it marked CRS
response as failed transaction (due to simplicity).

But pci-aardvark.c driver is already waiting up to the PIO_RETRY_CNT count
for PIO config response and so we can with a small change implement
re-issuing of config requests as described in PCIe base specification.

This change implements re-issuing of config requests when response is CRS.
Set upper bound of wait cycles to around PIO_RETRY_CNT, afterwards the
transaction is marked as failed and an all-ones value is returned as
before.

We do this by returning appropriate error codes from function
advk_pcie_check_pio_status(). On CRS we return -EAGAIN and caller then
reissues transaction.

Fixes: 43f5c77bcbd2 ("PCI: aardvark: Fix reporting CRS value")
Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Marek Behún <kabel@kernel.org>
---
drivers/pci/controller/pci-aardvark.c | 67 +++++++++++++++++----------
1 file changed, 43 insertions(+), 24 deletions(-)

diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
index 51d2955d9cca..7b9870d0b81f 100644
--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -603,6 +603,7 @@ static int advk_pcie_check_pio_status(struct advk_pcie *pcie, bool allow_crs, u3
u32 reg;
unsigned int status;
char *strcomp_status, *str_posted;
+ int ret;

reg = advk_readl(pcie, PIO_STAT);
status = (reg & PIO_COMPLETION_STATUS_MASK) >>
@@ -627,6 +628,7 @@ static int advk_pcie_check_pio_status(struct advk_pcie *pcie, bool allow_crs, u3
case PIO_COMPLETION_STATUS_OK:
if (reg & PIO_ERR_STATUS) {
strcomp_status = "COMP_ERR";
+ ret = -EFAULT;
break;
}
/* Get the read result */
@@ -634,9 +636,11 @@ static int advk_pcie_check_pio_status(struct advk_pcie *pcie, bool allow_crs, u3
*val = advk_readl(pcie, PIO_RD_DATA);
/* No error */
strcomp_status = NULL;
+ ret = 0;
break;
case PIO_COMPLETION_STATUS_UR:
strcomp_status = "UR";
+ ret = -EOPNOTSUPP;
break;
case PIO_COMPLETION_STATUS_CRS:
if (allow_crs && val) {
@@ -654,6 +658,7 @@ static int advk_pcie_check_pio_status(struct advk_pcie *pcie, bool allow_crs, u3
*/
*val = CFG_RD_CRS_VAL;
strcomp_status = NULL;
+ ret = 0;
break;
}
/* PCIe r4.0, sec 2.3.2, says:
@@ -669,21 +674,24 @@ static int advk_pcie_check_pio_status(struct advk_pcie *pcie, bool allow_crs, u3
* Request and taking appropriate action, e.g., complete the
* Request to the host as a failed transaction.
*
- * To simplify implementation do not re-issue the Configuration
- * Request and complete the Request as a failed transaction.
+ * So return -EAGAIN and caller (pci-aardvark.c driver) will
+ * re-issue request again up to the PIO_RETRY_CNT retries.
*/
strcomp_status = "CRS";
+ ret = -EAGAIN;
break;
case PIO_COMPLETION_STATUS_CA:
strcomp_status = "CA";
+ ret = -ECANCELED;
break;
default:
strcomp_status = "Unknown";
+ ret = -EINVAL;
break;
}

if (!strcomp_status)
- return 0;
+ return ret;

if (reg & PIO_NON_POSTED_REQ)
str_posted = "Non-posted";
@@ -693,7 +701,7 @@ static int advk_pcie_check_pio_status(struct advk_pcie *pcie, bool allow_crs, u3
dev_dbg(dev, "%s PIO Response Status: %s, %#x @ %#x\n",
str_posted, strcomp_status, reg, advk_readl(pcie, PIO_ADDR_LS));

- return -EFAULT;
+ return ret;
}

static int advk_pcie_wait_pio(struct advk_pcie *pcie)
@@ -701,13 +709,13 @@ static int advk_pcie_wait_pio(struct advk_pcie *pcie)
struct device *dev = &pcie->pdev->dev;
int i;

- for (i = 0; i < PIO_RETRY_CNT; i++) {
+ for (i = 1; i <= PIO_RETRY_CNT; i++) {
u32 start, isr;

start = advk_readl(pcie, PIO_START);
isr = advk_readl(pcie, PIO_ISR);
if (!start && isr)
- return 0;
+ return i;
udelay(PIO_RETRY_DELAY);
}

@@ -898,6 +906,7 @@ static int advk_pcie_rd_conf(struct pci_bus *bus, u32 devfn,
int where, int size, u32 *val)
{
struct advk_pcie *pcie = bus->sysdata;
+ int retry_count;
bool allow_crs;
u32 reg;
int ret;
@@ -940,16 +949,22 @@ static int advk_pcie_rd_conf(struct pci_bus *bus, u32 devfn,
/* Program the data strobe */
advk_writel(pcie, 0xf, PIO_WR_DATA_STRB);

- /* Clear PIO DONE ISR and start the transfer */
- advk_writel(pcie, 1, PIO_ISR);
- advk_writel(pcie, 1, PIO_START);
+ retry_count = 0;
+ do {
+ /* Clear PIO DONE ISR and start the transfer */
+ advk_writel(pcie, 1, PIO_ISR);
+ advk_writel(pcie, 1, PIO_START);

- ret = advk_pcie_wait_pio(pcie);
- if (ret < 0)
- goto try_crs;
+ ret = advk_pcie_wait_pio(pcie);
+ if (ret < 0)
+ goto try_crs;
+
+ retry_count += ret;
+
+ /* Check PIO status and get the read result */
+ ret = advk_pcie_check_pio_status(pcie, allow_crs, val);
+ } while (ret == -EAGAIN && retry_count < PIO_RETRY_CNT);

- /* Check PIO status and get the read result */
- ret = advk_pcie_check_pio_status(pcie, allow_crs, val);
if (ret < 0)
goto fail;

@@ -981,6 +996,7 @@ static int advk_pcie_wr_conf(struct pci_bus *bus, u32 devfn,
struct advk_pcie *pcie = bus->sysdata;
u32 reg;
u32 data_strobe = 0x0;
+ int retry_count;
int offset;
int ret;

@@ -1022,19 +1038,22 @@ static int advk_pcie_wr_conf(struct pci_bus *bus, u32 devfn,
/* Program the data strobe */
advk_writel(pcie, data_strobe, PIO_WR_DATA_STRB);

- /* Clear PIO DONE ISR and start the transfer */
- advk_writel(pcie, 1, PIO_ISR);
- advk_writel(pcie, 1, PIO_START);
+ retry_count = 0;
+ do {
+ /* Clear PIO DONE ISR and start the transfer */
+ advk_writel(pcie, 1, PIO_ISR);
+ advk_writel(pcie, 1, PIO_START);

- ret = advk_pcie_wait_pio(pcie);
- if (ret < 0)
- return PCIBIOS_SET_FAILED;
+ ret = advk_pcie_wait_pio(pcie);
+ if (ret < 0)
+ return PCIBIOS_SET_FAILED;

- ret = advk_pcie_check_pio_status(pcie, false, NULL);
- if (ret < 0)
- return PCIBIOS_SET_FAILED;
+ retry_count += ret;

- return PCIBIOS_SUCCESSFUL;
+ ret = advk_pcie_check_pio_status(pcie, false, NULL);
+ } while (ret == -EAGAIN && retry_count < PIO_RETRY_CNT);
+
+ return ret < 0 ? PCIBIOS_SET_FAILED : PCIBIOS_SUCCESSFUL;
}

static struct pci_ops advk_pcie_ops = {
--
2.32.0