Re: [PATCH v5] usb: host: xhci-plat: Set XHCI_SKIP_PHY_INIT quirk for DWC3 controller

From: Sandeep Maheswaram
Date: Wed Jan 26 2022 - 23:59:50 EST



On 1/26/2022 5:55 PM, Greg Kroah-Hartman wrote:
On Fri, Jan 07, 2022 at 10:27:59AM +0530, Sandeep Maheswaram wrote:
On 1/6/2022 7:55 PM, Greg Kroah-Hartman wrote:
On Wed, Dec 22, 2021 at 11:39:43AM +0530, Sandeep Maheswaram wrote:
Set XHCI_SKIP_PHY_INIT quirk to avoid phy initialization twice.
Runtime suspend of phy drivers was failing from DWC3 driver as runtime
usage value is 2 because the phy is initialized from DWC3 and HCD core.
DWC3 manages phy in their core drivers. Set this quirk to avoid phy
initialization in HCD core.

Signed-off-by: Sandeep Maheswaram <quic_c_sanm@xxxxxxxxxxx>
---
v5:
Added comment to explain the change done.
v4:
Changed pdev->dev.parent->of_node to sysdev->of_node

drivers/usb/host/xhci-plat.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index c1edcc9..e6014d4 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -327,6 +327,14 @@ static int xhci_plat_probe(struct platform_device *pdev)
&xhci->imod_interval);
}
+ /*
+ * Set XHCI_SKIP_PHY_INIT quirk to avoid phy initialization twice.
+ * DWC3 manages phy in their core drivers. Set this quirk to avoid phy
+ * initialization in HCD core.
+ */
+ if (of_device_is_compatible(sysdev->of_node, "snps,dwc3"))
+ xhci->quirks |= XHCI_SKIP_PHY_INIT;
+
Why is this function caring about dwc3 stuff? Shoudn't this be a
"generic" device property instead of this device-specific one?

thanks,

greg k-h
This quirk is set only if required for some controllers (eg: dwc3 & cdns3).

Please check below commit.

https://lore.kernel.org/all/20200918131752.16488-5-mathias.nyman@xxxxxxxxxxxxxxx/
That commit has nothing to do with a specific "dwc3" quirk anywhere.
Why not set this flag in the specific platform xhci driver instead where
it belongs?

thanks,

greg k-h

There is no specific xhci platform driver for dwc3 controllers.

dwc3 controllers use xhci-plat driver .

We can add this quirk in usb/dwc3/host.c as cdns3 does but that requires tying dwc3 and xhci driver .

https://patchwork.kernel.org/project/linux-arm-msm/patch/1633946518-13906-1-git-send-email-sanm@xxxxxxxxxxxxxx/

Regards

Sandeep