Re: [PATCH v2] usb: host: xhci-plat: fix support for XHCI_SKIP_PHY_INIT quirk

From: "Pali Rohár" <pali@kernel.org>
To: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>,
	Peter Chen <peter.chen@nxp.com>,
	Mathias Nyman <mathias.nyman@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jun Li <jun.li@nxp.com>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] usb: host: xhci-plat: fix support for XHCI_SKIP_PHY_INIT quirk
Date: Mon, 1 Feb 2021 16:11:53 +0100	[thread overview]
Message-ID: <20210201151153.zhk4tq5a3irnkahd@pali> (raw)
In-Reply-To: <20210126090606.svpamobnrbdxyhgg@pali>

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