Re: [PATCH] xhci: workaround for S3 issue on AMD SNPS 3.0 xHC

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Sep 16, 2020 at 12:28:40AM +0530, Singh, Sandeep wrote:
> On 8/31/2020 12:22 PM, 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
> > index 3feaafebfe58..865a16e6c1ed 100644
> > --- a/drivers/usb/host/xhci-pci.c
> > +++ b/drivers/usb/host/xhci-pci.c
> > @@ -160,6 +160,9 @@ static void xhci_pci_quirks(struct device *dev, struct xhci_hcd *xhci)
> >   	    (pdev->device == 0x15e0 || pdev->device == 0x15e1))
> >   		xhci->quirks |= XHCI_SNPS_BROKEN_SUSPEND;
> > +	if (pdev->vendor == PCI_VENDOR_ID_AMD && pdev->device == 0x15e5)
> > +		xhci->quirks |= XHCI_DISABLE_SPARSE;
> > +
> >   	if (pdev->vendor == PCI_VENDOR_ID_AMD)
> >   		xhci->quirks |= XHCI_TRUST_TX_LENGTH;
> > @@ -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);
> > +		writel(reg, hcd->regs + 0xC12C);
> > +	}
> > +
> >   	xhci->shared_hcd = usb_create_shared_hcd(&xhci_pci_hc_driver, &dev->dev,
> >   						 pci_name(dev), hcd);
> >   	if (!xhci->shared_hcd) {
> > diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> > index ea1754f185a2..ea966d70f1ee 100644
> > --- a/drivers/usb/host/xhci.h
> > +++ b/drivers/usb/host/xhci.h
> > @@ -1874,6 +1874,7 @@ struct xhci_hcd {
> >   #define XHCI_RESET_PLL_ON_DISCONNECT	BIT_ULL(34)
> >   #define XHCI_SNPS_BROKEN_SUSPEND    BIT_ULL(35)
> >   #define XHCI_RENESAS_FW_QUIRK	BIT_ULL(36)
> > +#define XHCI_DISABLE_SPARSE	BIT_ULL(37)
> >   	unsigned int		num_active_eps;
> >   	unsigned int		limit_active_eps;
> 
> Any feedback on this patch?

Do you agree with it?  If so, can you review it and say so please?

thanks,

greg k-h