linux-kernel - Re: [PATCH v2 5/9] usb: xhci-pci: Add support for reset controllers

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Date:   Wed, 10 Jun 2020 17:49:28 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Florian Fainelli <f.fainelli@...il.com>,
        gregkh@...uxfoundation.org, wahrenst@....net,
        p.zabel@...gutronix.de, linux-kernel@...r.kernel.org,
        Mathias Nyman <mathias.nyman@...el.com>
Cc:     tim.gover@...pberrypi.org, mathias.nyman@...ux.intel.com,
        linux-pci@...r.kernel.org, linux-usb@...r.kernel.org,
        andy.shevchenko@...il.com, lorenzo.pieralisi@....com,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org, helgaas@...nel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 5/9] usb: xhci-pci: Add support for reset controllers

Hi Florian,

On Tue, 2020-06-09 at 11:13 -0700, Florian Fainelli wrote:
> 
> On 6/9/2020 10:49 AM, Nicolas Saenz Julienne wrote:
> > Some atypical users of xhci-pci might need to manually reset their xHCI
> > controller before starting the HCD setup. Check if a reset controller
> > device is available to the PCI bus and trigger a reset.
> > 
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> > 
> > ---
> > 
> > Changes since v1:
> >  - Use proper reset API
> >  - Make code simpler
> > 
> >  drivers/usb/host/xhci-pci.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
> > index ef513c2fb843..6e96affa4ceb 100644
> > --- a/drivers/usb/host/xhci-pci.c
> > +++ b/drivers/usb/host/xhci-pci.c
> > @@ -12,6 +12,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/module.h>
> >  #include <linux/acpi.h>
> > +#include <linux/reset.h>
> >  
> >  #include "xhci.h"
> >  #include "xhci-trace.h"
> > @@ -339,6 +340,7 @@ static int xhci_pci_probe(struct pci_dev *dev, const
> > struct pci_device_id *id)
> >  	struct xhci_hcd *xhci;
> >  	struct usb_hcd *hcd;
> >  	struct xhci_driver_data *driver_data;
> > +	struct reset_control *reset;
> >  
> >  	driver_data = (struct xhci_driver_data *)id->driver_data;
> >  	if (driver_data && driver_data->quirks & XHCI_RENESAS_FW_QUIRK) {
> > @@ -347,6 +349,11 @@ static int xhci_pci_probe(struct pci_dev *dev, const
> > struct pci_device_id *id)
> >  			return retval;
> >  	}
> >  
> > +	reset = devm_reset_control_get_optional_exclusive(&dev->bus->dev, NULL);
> > +	if (IS_ERR(reset))
> > +		return PTR_ERR(reset);
> > +	reset_control_reset(reset);
> 
> Sorry for not catching this earlier, since this is a generic integration
> with the reset controller API, should not you also add a
> reset_control_reset() to hcd_pci_resume() for symmetry?

Agreed, if the RPi4 supported suspend/resume, which AFAIK doesn't, an extra
reset would be needed as pcie-brcmstb performs a fundamental reset on resume
forcing us to reinitialize vl805.

Thanks!
Nicolas


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