[PATCH 1/1] PCI/DPC: Fix TLP Prefix register reading offset

[PATCH 1/1] PCI/DPC: Fix TLP Prefix register reading offset

[Ilpo Järvinen]

The TLP Prefix Log Register consists of multiple DWORDs (PCIe r6.1 sec
7.9.14.13) but the loop in dpc_process_rp_pio_error() keeps reading
from the first DWORD. Add the iteration count based offset calculation
into the config read.

Fixes: f20c4ea49ec4 ("PCI/DPC: Add eDPC support")
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/pci/pcie/dpc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index 94111e438241..e5d7c12854fa 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -234,7 +234,7 @@ static void dpc_process_rp_pio_error(struct pci_dev *pdev)
 
 	for (i = 0; i < pdev->dpc_rp_log_size - 5; i++) {
 		pci_read_config_dword(pdev,
-			cap + PCI_EXP_DPC_RP_PIO_TLPPREFIX_LOG, &prefix);
+			cap + PCI_EXP_DPC_RP_PIO_TLPPREFIX_LOG + i * 4, &prefix);
 		pci_err(pdev, "TLP Prefix Header: dw%d, %#010x\n", i, prefix);
 	}
  clear_status:
-- 
2.39.2

Re: [PATCH 1/1] PCI/DPC: Fix TLP Prefix register reading offset

[Bjorn Helgaas]

On Thu, Jan 18, 2024 at 01:08:15PM +0200, Ilpo Järvinen wrote:
> The TLP Prefix Log Register consists of multiple DWORDs (PCIe r6.1 sec
> 7.9.14.13) but the loop in dpc_process_rp_pio_error() keeps reading
> from the first DWORD. Add the iteration count based offset calculation
> into the config read.

So IIUC the user-visible bug is that we print only the first PIO TLP
Prefix (duplicated several times), and we never print the second,
third, etc Prefixes, right?

I wish we could print them all in a single pci_err(), as we do for the
TLP Header Log, instead of dribbling them out one by one.

> Fixes: f20c4ea49ec4 ("PCI/DPC: Add eDPC support")
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> ---
>  drivers/pci/pcie/dpc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> index 94111e438241..e5d7c12854fa 100644
> --- a/drivers/pci/pcie/dpc.c
> +++ b/drivers/pci/pcie/dpc.c
> @@ -234,7 +234,7 @@ static void dpc_process_rp_pio_error(struct pci_dev *pdev)
>  
>  	for (i = 0; i < pdev->dpc_rp_log_size - 5; i++) {
>  		pci_read_config_dword(pdev,
> -			cap + PCI_EXP_DPC_RP_PIO_TLPPREFIX_LOG, &prefix);
> +			cap + PCI_EXP_DPC_RP_PIO_TLPPREFIX_LOG + i * 4, &prefix);
>  		pci_err(pdev, "TLP Prefix Header: dw%d, %#010x\n", i, prefix);
>  	}
>   clear_status:
> -- 
> 2.39.2
> 

Re: [PATCH 1/1] PCI/DPC: Fix TLP Prefix register reading offset

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 1011 bytes --]

On Fri, 19 Jan 2024, Bjorn Helgaas wrote:

> On Thu, Jan 18, 2024 at 01:08:15PM +0200, Ilpo Järvinen wrote:
> > The TLP Prefix Log Register consists of multiple DWORDs (PCIe r6.1 sec
> > 7.9.14.13) but the loop in dpc_process_rp_pio_error() keeps reading
> > from the first DWORD. Add the iteration count based offset calculation
> > into the config read.
> 
> So IIUC the user-visible bug is that we print only the first PIO TLP
> Prefix (duplicated several times), and we never print the second,
> third, etc Prefixes, right?

Yes.

> I wish we could print them all in a single pci_err(), as we do for the
> TLP Header Log, instead of dribbling them out one by one.

I've also done some work towards consolidating AER and DPC TLP 
Header/Prefix Log handling which is when I found this bug (the reading 
side is already done but printing is still pending).

> > Fixes: f20c4ea49ec4 ("PCI/DPC: Add eDPC support")
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

-- 
 i.

Re: [PATCH 1/1] PCI/DPC: Fix TLP Prefix register reading offset

[Bjorn Helgaas]

On Thu, Jan 18, 2024 at 01:08:15PM +0200, Ilpo Järvinen wrote:
> The TLP Prefix Log Register consists of multiple DWORDs (PCIe r6.1 sec
> 7.9.14.13) but the loop in dpc_process_rp_pio_error() keeps reading
> from the first DWORD. Add the iteration count based offset calculation
> into the config read.
> 
> Fixes: f20c4ea49ec4 ("PCI/DPC: Add eDPC support")
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Applied to pci/dpc for v6.9 with commit log below, thanks!

    PCI/DPC: Print all TLP Prefixes, not just the first
    
    The TLP Prefix Log Register consists of multiple DWORDs (PCIe r6.1 sec
    7.9.14.13) but the loop in dpc_process_rp_pio_error() keeps reading from
    the first DWORD, so we print only the first PIO TLP Prefix (duplicated
    several times), and we never print the second, third, etc., Prefixes.
    
    Add the iteration count based offset calculation into the config read.
    
    Fixes: f20c4ea49ec4 ("PCI/DPC: Add eDPC support")
    Link: https://lore.kernel.org/r/20240118110815.3867-1-ilpo.jarvinen@linux.intel.com
    Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
    [bhelgaas: add user-visible details to commit log]
    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

> ---
>  drivers/pci/pcie/dpc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> index 94111e438241..e5d7c12854fa 100644
> --- a/drivers/pci/pcie/dpc.c
> +++ b/drivers/pci/pcie/dpc.c
> @@ -234,7 +234,7 @@ static void dpc_process_rp_pio_error(struct pci_dev *pdev)
>  
>  	for (i = 0; i < pdev->dpc_rp_log_size - 5; i++) {
>  		pci_read_config_dword(pdev,
> -			cap + PCI_EXP_DPC_RP_PIO_TLPPREFIX_LOG, &prefix);
> +			cap + PCI_EXP_DPC_RP_PIO_TLPPREFIX_LOG + i * 4, &prefix);
>  		pci_err(pdev, "TLP Prefix Header: dw%d, %#010x\n", i, prefix);
>  	}
>   clear_status:
> -- 
> 2.39.2
>