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

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Message-ID: <20210201151153.zhk4tq5a3irnkahd@pali>
Date:   Mon, 1 Feb 2021 16:11:53 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Cc:     Mathias Nyman <mathias.nyman@...ux.intel.com>,
        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

On Tuesday 26 January 2021 10:06:06 Pali Rohár wrote:
> On Tuesday 26 January 2021 04:27:37 Yoshihiro Shimoda wrote:
> > Hi Pali,
> > > > 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.
> 
> Ok, thank you for testing! I will try to come up with other solution to
> mentioned mvebu-xhci issue.

Hello! New version of this patch is in following thread, please review it:
"[PATCH v2] usb: host: xhci: mvebu: make USB 3.0 PHY optional for Armada 3720"
https://lore.kernel.org/linux-usb/20210201150803.7305-1-pali@kernel.org/

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