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SubjectRe: [PATCH v3 1/2] PCI: pciehp: Add support for async hotplug with native AER and DPC/EDR
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On 6/22/2023 2:04 AM, Lukas Wunner wrote:
> On Wed, Jun 21, 2023 at 06:51:51PM +0000, Smita Koralahalli wrote:
>> --- a/drivers/pci/pcie/dpc.c
>> +++ b/drivers/pci/pcie/dpc.c
>> @@ -292,10 +292,68 @@ void dpc_process_error(struct pci_dev *pdev)
>> }
>> }
>>
>> +static void pci_clear_surpdn_errors(struct pci_dev *pdev)
>> +{
>> + u16 reg16;
>> + u32 reg32;
>> +
>> + pci_read_config_dword(pdev, pdev->dpc_cap + PCI_EXP_DPC_RP_PIO_STATUS, &reg32);
>> + pci_write_config_dword(pdev, pdev->dpc_cap + PCI_EXP_DPC_RP_PIO_STATUS, reg32);
>
> Make this read+write conditional on "if (pdev->dpc_rp_extensions)"
> as the register otherwise doesn't exist.

I'm checking for pdev->dpc_rpc_extensions inside
dpc_handle_surprise_removal() before calling pci_clear_surpdn_errors().
Should I recheck it once again here?

>
> Wrap to 80 chars per line.

Okay.

>
>
>> + pci_read_config_word(pdev, PCI_STATUS, &reg16);
>> + pci_write_config_word(pdev, PCI_STATUS, reg16);
>> +
>> + pcie_capability_write_word(pdev, PCI_EXP_DEVSTA, PCI_EXP_DEVSTA_FED);
>> +}
>
> A code comment might be useful here saying that in practice,
> Surprise Down errors have been observed to also set error bits
> in the Status Register as well as the Fatal Error Detected bit
> in the Device Status Register.

And probably move this code comment below to where this function is
called inside dpc_handle_surprise_removal()..?

>
>
>> +static void dpc_handle_surprise_removal(struct pci_dev *pdev)
>> +{
>
> I'm wondering if we also need
>
> if (!pcie_wait_for_link(pdev, false)) {
> pci_info(pdev, "Data Link Layer Link Active not cleared in 1000 msec\n");
> goto out;
> }
>
> here, similar to dpc_reset_link() and in accordance with PCIe r6.1
> sec 6.2.11:
>
> "To ensure that the LTSSM has time to reach the Disabled state
> or at least to bring the Link down under a variety of error
> conditions, software must leave the Downstream Port in DPC
> until the Data Link Layer Link Active bit in the Link Status
> Register reads 0b; otherwise, the result is undefined."

And include the above comment in code..
>
>
>> + if (pdev->dpc_rp_extensions && dpc_wait_rp_inactive(pdev)) {
>> + pci_err(pdev, "failed to retrieve DPC root port on async remove\n");
>> + goto out;
>> + }
>
> I don't think pci_err() is needed here as dpc_wait_rp_inactive()
> already emits a message. (I think I mistakenly gave the advice
> to emit an error here in an earlier review comment -- sorry!)

:)

Will take care of other comments below as well.

Thanks,
Smita

>>
>> /* We configure DPC so it only triggers on ERR_FATAL */
>> --
>> 2.17.1
>>

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