linux-kernel - RE: [PATCH v2] usb: host: xhci-plat: fix support for XHCI_SKIP_PHY

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Message-ID: <TY2PR01MB369295E3D3BF6D5700EC50CCD8BC0@TY2PR01MB3692.jpnprd01.prod.outlook.com>
Date:   Tue, 26 Jan 2021 04:27:37 +0000
From:   Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
To:     Pali Rohár <pali@...nel.org>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>
CC:     Peter Chen <peter.chen@....com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jun Li <jun.li@....com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] usb: host: xhci-plat: fix support for
 XHCI_SKIP_PHY_INIT quirk

Hi Pali,

> From: Pali Rohár, Sent: Monday, January 25, 2021 11:20 PM
> On Friday 15 January 2021 15:32:30 Mathias Nyman wrote:
> > On 14.1.2021 1.20, Pali Rohár wrote:
> > > On Thursday 24 December 2020 05:59:05 Peter Chen wrote:
> > >> On 20-12-23 17:18:47, Pali Rohár wrote:
> > >>> Currently init_quirk callbacks for xhci platform drivers are called
> > >>> xhci_plat_setup() function which is called after chip reset completes.
> > >>> It happens in the middle of the usb_add_hcd() function.
> > >>>
> > >>> But XHCI_SKIP_PHY_INIT quirk is checked in the xhci_plat_probe() function
> > >>> prior calling usb_add_hcd() function. Therefore this XHCI_SKIP_PHY_INIT
> > >>> currently does nothing as prior xhci_plat_setup() it is not set.
> > >>>
> > >>> Quirk XHCI_SKIP_PHY_INIT is only setting hcd->skip_phy_initialization value
> > >>> which really needs to be set prior calling usb_add_hcd() as this function
> > >>> at its beginning skips PHY init if this member is set.
> > >>>
> > >>> This patch fixes implementation of the XHCI_SKIP_PHY_INIT quirk by calling
> > >>> init_quirk callbacks (via xhci_priv_init_quirk()) prior checking if
> > >>> XHCI_SKIP_PHY_INIT is set. Also checking if either xhci->quirks or
> > >>> priv->quirks contains this XHCI_SKIP_PHY_INIT quirk.
> > >>>
> > >>> Signed-off-by: Pali Rohár <pali@...nel.org>
> > >>>
> > >>> ---
> > >>> Changes in v2:
> > >>> * Check also xhci->quirks as xhci_priv_init_quirk() callbacks are setting xhci->quirks
> > >>> * Tested with "usb: host: xhci: mvebu: make USB 3.0 PHY optional for Armada 3720" patch
> > >>> * Removed Fixes: line
> > >>> ---
> > >>>  drivers/usb/host/xhci-plat.c | 16 ++++++++--------
> > >>>  1 file changed, 8 insertions(+), 8 deletions(-)
> > >>>
> > >>> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> > >>> index 4d34f6005381..0eab7cb5a767 100644
> > >>> --- a/drivers/usb/host/xhci-plat.c
> > >>> +++ b/drivers/usb/host/xhci-plat.c
> > >>> @@ -89,13 +89,6 @@ static void xhci_plat_quirks(struct device *dev, struct xhci_hcd *xhci)
> > >>>  /* called during probe() after chip reset completes */
> > >>>  static int xhci_plat_setup(struct usb_hcd *hcd)
> > >>>  {
> > >>> -	int ret;
> > >>> -
> > >>> -
> > >>> -	ret = xhci_priv_init_quirk(hcd);
> > >>> -	if (ret)
> > >>> -		return ret;
> > >>> -
> > >>>  	return xhci_gen_setup(hcd, xhci_plat_quirks);
> > >>>  }
> > >>>
> > >>> @@ -330,7 +323,14 @@ static int xhci_plat_probe(struct platform_device *pdev)
> > >>>
> > >>>  	hcd->tpl_support = of_usb_host_tpl_support(sysdev->of_node);
> > >>>  	xhci->shared_hcd->tpl_support = hcd->tpl_support;
> > >>> -	if (priv && (priv->quirks & XHCI_SKIP_PHY_INIT))
> > >>> +
> > >>> +	if (priv) {
> > >>> +		ret = xhci_priv_init_quirk(hcd);
> > >>> +		if (ret)
> > >>> +			goto disable_usb_phy;
> > >>> +	}
> > >>> +
> > >>> +	if ((xhci->quirks & XHCI_SKIP_PHY_INIT) || (priv && (priv->quirks & XHCI_SKIP_PHY_INIT)))
> > >>>  		hcd->skip_phy_initialization = 1;
> > >>
> > >> I am not sure if others agree with you move the position of
> > >> xhci_priv_init_quirk, Let's see Mathias opinion.
> > >
> > > Hello! Do you have an opinion how to handle this issue? As currently it
> > > is needed for another patch which is fixing issue/regression in xhci-mvebu:
> > >
<snip>
> > >
> >
> > I can see the benefit in this.
> > In the xhci-plat case usb_create_hcd and usb_add_hcd are separate steps, and
> > we could both copy the xhci_plat_priv .quirks and run the .init_qurks before
> > adding the hcd.
> > I guess the current way is inherited from pci case where the earliest place
> > to do this after hcd is created is the hcd->driver->reset callback (which is
> > set to xhci_pci_setup() or xhci_plat_setup()).
> >
> > xhci-rcar.c is using the .init_quirk to load firmware, we need to check with
> > them if this change is ok. (added Yoshihiro Shimoda to cc)
> 
> Yoshihiro, is this change OK?
> 
> Can we move forward? I really need to now how to handle regression in
> xhci-mvebu driver. And one option is with this patch...

Thank you for asking me about this topic. I tested the patch, but unfortunately,
this patch is possible to break a rcar platform because a phy initialization is
needed before the firmware loading if the platform uses the phy. (Note that
upstream code (salvator-common.dtsi) doesn't use the phy for xhci. But,
if we use the phy on other board with this patch, the xhci will not work.)

So, I think we need to add a new function pointer for your case.

Best regards,
Yoshihiro Shimoda

> > Their firmware would be loaded before phy parts are initialized, usb bus
> > registered, or roothub device allocated.
> >
> > Thanks
> > -Mathias