linux-kernel - Re: [PATCH v8 3/5] usb: xhci: Add support for Renesas controller with memory

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Date:   Wed, 1 Apr 2020 18:27:48 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc:     Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-msm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Christian Lamparter <chunkeey@...glemail.com>,
        John Stultz <john.stultz@...aro.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Andreas Böhler <dev@...ehler.at>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 3/5] usb: xhci: Add support for Renesas controller
 with memory

On 26-03-20, 17:21, Vinod Koul wrote:
> On 26-03-20, 13:29, Mathias Nyman wrote:
> > Hi Vinod
> > 
> > On 23.3.2020 19.05, Vinod Koul wrote:
> > > Some rensas controller like uPD720201 and uPD720202 need firmware to be
> > > loaded. Add these devices in table and invoke renesas firmware loader
> > > functions to check and load the firmware into device memory when
> > > required.
> > > 
> > > Signed-off-by: Vinod Koul <vkoul@...nel.org>
> > > ---
> > >  drivers/usb/host/xhci-pci-renesas.c |  1 +
> > >  drivers/usb/host/xhci-pci.c         | 29 ++++++++++++++++++++++++++++-
> > >  drivers/usb/host/xhci-pci.h         |  3 +++
> > >  3 files changed, 32 insertions(+), 1 deletion(-)
> > > 
> > 
> > It's unfortunate if firmware loading couldn't be initiated in a PCI fixup hook
> > for this Renesas controller. What was the reason it failed?
> > 
> > Nicolas Saenz Julienne just submitted a solution like that for Raspberry Pi 4
> > where firmware loading is initiated in pci-quirks.c quirk_usb_early_handoff()
> > 
> > https://lore.kernel.org/lkml/20200324182812.20420-1-nsaenzjulienne@suse.de
> > 
> > Is he doing something different than what was done for the Renesas controller?
> 
> I tried and everytime ended up not getting firmware. Though I did not
> investigate a lot. Christian seemed to have tested sometime back as
> well.
> 
> Another problem is that we dont get driver_data in the quirk and there
> didnt seem a way to find the firmware name.
> 
> > > diff --git a/drivers/usb/host/xhci-pci-renesas.c b/drivers/usb/host/xhci-pci-renesas.c
> > > index c588277ac9b8..d413d53df94b 100644
> > > --- a/drivers/usb/host/xhci-pci-renesas.c
> > > +++ b/drivers/usb/host/xhci-pci-renesas.c
> > > @@ -336,6 +336,7 @@ static void renesas_fw_callback(const struct firmware *fw,
> > >  		goto cleanup;
> > >  	}
> > >  
> > > +	xhci_pci_probe(pdev, ctx->id);
> > >  	return;
> > 
> > I haven't looked into this but instead of calling xhci_pci_probe() here in the async fw
> > loading callback could we just return -EPROBE_DEFER until firmware is loaded when
> > xhci_pci_probe() is originally called?
> 
> Hmm, initially my thinking was how to tell device core to probe again,
> and then digging up I saw wait_for_device_probe() which can be used, let
> me try that

Sorry to report back that it doesn't work as planned :(

I modified the code to invoke the request_firmware_nowait() which will load
the firmware and provide the firmware in callback. Meanwhile return -EPROBE_DEFER.

After a bit, the core invokes the driver probe again and we hit the
roadblock. The request_firmware uses devres and allocates resources for
loading the firmware. The problem is that device core checks for this:

bus: 'pci': really_probe: probing driver xhci_hcd_pci with device 0000:01:00.0
pci 0000:01:00.0: Resources present before probing

And here the probe fails. In some cases the firmware_callback finishes
before this and we can probe again, but that is not very reliable.

I tested another way to use request_firmware() (sync version) and then
load the firmware in probe and load. The request is done only for
renesas devices if they dont have firmware already running.
So rest of the devices wont have any impact.

Now should we continue this way in the patchset or move to sync version.
Am okay either way.

-- 
~Vinod