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

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Message-ID: <cb7182c6-0236-26f2-4f96-9bc001994728@ti.com>
Date:   Tue, 14 Feb 2017 14:26:49 +0200
From:   Roger Quadros <rogerq@...com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     Peter Chen <peter.chen@....com>,
        gregkh <gregkh@...uxfoundation.org>, <stern@...land.harvard.edu>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Mark Brown <broonie@...nel.org>, <sre@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>, <rjw@...ysocki.net>,
        <dbaryshkov@...il.com>, Mark Rutland <mark.rutland@....com>,
        Heiko Stuebner <heiko@...ech.de>, <stephen.boyd@...aro.org>,
        <frank.li@....com>, <gary.bisson@...ndarydevices.com>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Sriram Dash <sriram.dash@....com>, <festevam@...il.com>,
        <stillcompiling@...il.com>, <vaibhav.hiremath@...aro.org>,
        Krzysztof Kozlowski <krzk@...nel.org>, <mka@...omium.org>,
        <devicetree@...r.kernel.org>, <mail@...iej.szmigiero.name>,
        <pawel.moll@....com>, <linux-pm@...r.kernel.org>,
        <s.hauer@...gutronix.de>, <troy.kisky@...ndarydevices.com>,
        Alexander Sverdlin <alexander.sverdlin@...ia.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        <hverkuil@...all.nl>, <oscar@...andei.net>,
        Baolin Wang <baolin.wang@...aro.org>,
        <linux-usb@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        <p.zabel@...gutronix.de>, <jun.li@....com>
Subject: Re: [PATCH v13 06/12] usb: xhci: use bus->sysdev for DMA
 configuration

On 14/02/17 13:44, Arnd Bergmann wrote:
> On Tue, Feb 14, 2017 at 11:36 AM, Roger Quadros <rogerq@...com> wrote:
>> On 11/02/17 03:27, Peter Chen wrote:
>>> From: Arnd Bergmann <arnd@...db.de>
>>>
>>> For xhci-hcd platform device, all the DMA parameters are not
>>> configured properly, notably dma ops for dwc3 devices. So, set
>>> the dma for xhci from sysdev. sysdev is pointing to device that
>>> is known to the system firmware or hardware.
>>>
>>> Cc: Baolin Wang <baolin.wang@...aro.org>
>>> Cc: Vivek Gautam <vivek.gautam@...eaurora.org>
>>> Cc: Alexander Sverdlin <alexander.sverdlin@...ia.com>
>>> Cc: Mathias Nyman <mathias.nyman@...ux.intel.com>
>>>
>>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>>> Signed-off-by: Sriram Dash <sriram.dash@....com>
>>> ---
>>> Hi, Baolin, Vivek and Alexander,
>>> I removed your tested-by tag due to add one change that adding sysdev
>>> for shared hcd too, if your test shows this change works for you or
>>> has no effect for you, please consider adding tested-by tag again,
>>> thanks.
> 
>>> @@ -222,20 +241,20 @@ static int xhci_plat_probe(struct platform_device *pdev)
>>>
>>>       xhci->clk = clk;
>>>       xhci->main_hcd = hcd;
>>> -     xhci->shared_hcd = usb_create_shared_hcd(driver, &pdev->dev,
>>> +     xhci->shared_hcd = __usb_create_hcd(driver, sysdev, &pdev->dev,
>>>                       dev_name(&pdev->dev), hcd);
>>>       if (!xhci->shared_hcd) {
>>>               ret = -ENOMEM;
>>>               goto disable_clk;
>>>       }
>>>
>>> -     if (device_property_read_bool(&pdev->dev, "usb3-lpm-capable"))
>>> +     if (device_property_read_bool(sysdev, "usb3-lpm-capable"))
>>
>> 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.

-- 
cheers,
-roger