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SubjectRe: [PATCH] xhci: workaround for S3 issue on AMD SNPS 3.0 xHC
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On 16.9.2020 11.06, Greg KH wrote:
> On Mon, Aug 31, 2020 at 06:52:46AM +0000, Nehal Bakulchandra Shah wrote:
>> From: Nehal Bakulchandra Shah <Nehal-Bakulchandra.shah@amd.com>
>>
>> On some platform of AMD, S3 fails with HCE and SRE errors.To fix this,
>> sparse controller enable bit has to be disabled.
>>
>> Signed-off-by: Nehal Bakulchandra Shah <Nehal-Bakulchandra.shah@amd.com>
>> ---
>> drivers/usb/host/xhci-pci.c | 12 ++++++++++++
>> drivers/usb/host/xhci.h | 1 +
>> 2 files changed, 13 insertions(+)
>>
>> diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
>> @@ -371,6 +374,15 @@ static int xhci_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
>> /* USB 2.0 roothub is stored in the PCI device now. */
>> hcd = dev_get_drvdata(&dev->dev);
>> xhci = hcd_to_xhci(hcd);
>> +
>> + if (xhci->quirks & XHCI_DISABLE_SPARSE) {
>> + u32 reg;
>> +
>> + reg = readl(hcd->regs + 0xC12C);
>> + reg &= ~BIT(17);
>
> And is this the proper place to be testing for quirks and applying them?
> Why not do the above in the xhci_pci_quirks() call?

xhci_pci_quirks() is a confusing name, it actually only sets quirk flags based on PCI
vendor/device.

Anyway, point is still valid, this level of bitops in probe isn't very nice.
Turn it into a separate function, and call it from xhci_pci_setup(), or if flag
needs to be cleared more often, and is related to S3 problems then possibly from xhci_pci_suspend()

-Mathias

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