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

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Date: Fri, 19 Jan 2024 16:59:23 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
	Oliver O'Halloran <oohall@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Keith Busch <kbusch@...nel.org>,
	Dongdong Liu <liudongdong3@...wei.com>,
	linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] PCI/DPC: Fix TLP Prefix register reading offset

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@...ux.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
>