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

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Date:   Wed, 15 Feb 2017 12:10:22 +0200
From:   Roger Quadros <rogerq@...com>
To:     Peter Chen <hzpeterchen@...il.com>, Felipe Balbi <balbi@...nel.org>
CC:     Arnd Bergmann <arnd@...db.de>, 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

+Felipe,

On 15/02/17 10:51, Peter Chen wrote:
> On Wed, Feb 15, 2017 at 10:18:03AM +0200, Roger Quadros wrote:
>> Peter,
>>
>> On 15/02/17 03:35, Peter Chen wrote:
>>> 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?
>>
>> dwc3 is not setting "snps,usb3_lpm_capable" but "usb3-lpm-capable" for the
>> xhci platform device.
>>
>> What did you mean by firmware? Did you mean something like BIOS?
>> At least TI platforms don't use any firmware like BIOS. So dwc3 driver
>> needs to create a platform device for xhci on the fly and set the DT properties.
>>
> 
> By readying code, the dwc3 calls dwc3_get_properties to set
> dwc->usb3_lpm_capable, and at dwc3/host.c, it sets property
> "usb3-lpm-capable" according to this flag, why not let common
> code xhci-plat.c to get this property from sysdev which is DT
> nodes for dwc3?
> 

Felipe, any comments?

-- 
cheers,
-roger