linux-kernel - Re: [PATCH v13 06/12] usb: xhci: use bus->sysdev for DMA configuration

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Message-ID: <20170215013514.GA6579@b29397-desktop>
Date:   Wed, 15 Feb 2017 09:35:14 +0800
From:   Peter Chen <hzpeterchen@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Roger Quadros <rogerq@...com>, Mark Rutland <mark.rutland@....com>,
        Peter Chen <peter.chen@....com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Heiko Stuebner <heiko@...ech.de>, stephen.boyd@...aro.org,
        frank.li@....com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        gary.bisson@...ndarydevices.com,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Sriram Dash <sriram.dash@....com>, festevam@...il.com,
        stillcompiling@...il.com, dbaryshkov@...il.com,
        vaibhav.hiremath@...aro.org, Krzysztof Kozlowski <krzk@...nel.org>,
        mka@...omium.org, stern@...land.harvard.edu,
        devicetree@...r.kernel.org, mail@...iej.szmigiero.name,
        pawel.moll@....com, linux-pm@...r.kernel.org,
        s.hauer@...gutronix.de, troy.kisky@...ndarydevices.com,
        Rob Herring <robh+dt@...nel.org>,
        Alexander Sverdlin <alexander.sverdlin@...ia.com>,
        oscar@...andei.net,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        hverkuil@...all.nl, Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Baolin Wang <baolin.wang@...aro.org>,
        gregkh <gregkh@...uxfoundation.org>, linux-usb@...r.kernel.org,
        rjw@...ysocki.net, sre@...nel.org, Mark Brown <broonie@...nel.org>,
        p.zabel@...gutronix.de, Shawn Guo <shawnguo@...nel.org>,
        jun.li@....com
Subject: Re: [PATCH v13 06/12] usb: xhci: use bus->sysdev for DMA
 configuration

On Tue, Feb 14, 2017 at 01:58:40PM +0100, Arnd Bergmann wrote:
> On Tue, Feb 14, 2017 at 1:26 PM, Roger Quadros <rogerq@...com> wrote:
> > On 14/02/17 13:44, Arnd Bergmann wrote:
> >> On Tue, Feb 14, 2017 at 11:36 AM, Roger Quadros <rogerq@...com> wrote:
> 
> >>> Why are we using sysdev to read DT property? We should be using the
> >>> XHCI device (&pdev->dev) here, no?
> >>
> >> If I remember correctly, this is one of the cases where pdev does not
> >> have a device node attached to it because it was created by the driver
> >> of the parent device on the fly in case of dwc3. When you have a pure xhci
> >> device in DT, the two pointers are the same.
> >
> > From drivers/usb/dwc3/host.c
> >
> >>         if (dwc->usb3_lpm_capable) {
> >>                 props[0].name = "usb3-lpm-capable";
> >>                 ret = platform_device_add_properties(xhci, props);
> >>                 if (ret) {
> >>                         dev_err(dwc->dev, "failed to add properties to xHCI\n");
> >>                         goto err1;
> >>                 }
> >>         }
> >
> > So it is setting the usb3-lpm-capable property into the xhci platform device
> > and we should be reading the property from there.

Why dwc3 needs another "snps,usb3_lpm_capable"? Why not using
"usb3-lpm-capable" at firmware directly?

Peter

> 
> Hmm, ideally we would only have properties on one of the two, since we
> refer to the sysdev for the properties regarding DMA and PHY among other
> things, but I guess that's not an option here, since we can't call
> platform_device_add_properties() on a dwc_pci device and have to
> use the xhci pdev instead.
> 
>      Arnd
> 
-- 

Best Regards,
Peter Chen