linux-kernel - Re: [PATCH v3 03/22] usb: ulpi: Support device discovery via device properties

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Date:   Fri, 2 Sep 2016 18:14:25 -0700
From:   Stephen Boyd <stephen.boyd@...aro.org>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Linux USB List <linux-usb@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Andy Gross <andy.gross@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Arnd Bergmann <arnd@...db.de>, Felipe Balbi <balbi@...nel.org>,
        Peter Chen <peter.chen@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v3 03/22] usb: ulpi: Support device discovery via device properties

On Fri, Sep 2, 2016 at 7:09 AM, Heikki Krogerus
<heikki.krogerus@...ux.intel.com> wrote:
> Hi,
>
> On Wed, Aug 31, 2016 at 05:40:17PM -0700, Stephen Boyd wrote:
>> @@ -174,14 +219,37 @@ static int ulpi_register(struct device *dev, struct ulpi *ulpi)
>>       ulpi->id.product = ulpi_read(ulpi, ULPI_PRODUCT_ID_LOW);
>>       ulpi->id.product |= ulpi_read(ulpi, ULPI_PRODUCT_ID_HIGH) << 8;
>>
>> +     return 0;
>> +}
>> +
>> +static int ulpi_register(struct device *dev, struct ulpi *ulpi)
>> +{
>> +     int ret;
>> +
>>       ulpi->dev.parent = dev;
>>       ulpi->dev.bus = &ulpi_bus;
>>       ulpi->dev.type = &ulpi_dev_type;
>>       dev_set_name(&ulpi->dev, "%s.ulpi", dev_name(dev));
>>
>> +     if (IS_ENABLED(CONFIG_OF)) {
>
> I don't think you need to check that in this case.
>
>> +             ret = ulpi_of_register(ulpi);
>> +             if (ret)
>> +                     return ret;
>> +     }
>> +
>>       ACPI_COMPANION_SET(&ulpi->dev, ACPI_COMPANION(dev));
>
> ACPI_COMPANION_SET will overwrite the primary fwnode unconditionally,
> so just to play it safe, do this before you call ulpi_of_register().

Ok.

>
>> -     request_module("ulpi:v%04xp%04x", ulpi->id.vendor, ulpi->id.product);
>> +     ret = ulpi_read_id(ulpi);
>> +     /*
>> +      * Ignore failure in case of DT node because the device may
>> +      * not be powered up yet but we can still match by compatible
>> +      */
>> +     if (ret && !ulpi->dev.of_node)
>> +             return ret;
>> +
>> +     if (of_device_request_module(&ulpi->dev))
>> +             request_module("ulpi:v%04xp%04x", ulpi->id.vendor,
>> +                            ulpi->id.product);
>
> I don't think this works in all cases. If of_device_request_module()
> fails and we don't have the id.vendor/product set, we should not
> register the device. It also looks a bit messy.
>
> How about just using of_device_request_module() call as fallback in
> ulpi_read_id() and moving also request_module() call there:

Sure I'll fold it in and test. Should we "goto err" if we can't read
the scratch register though? I would think that's a "real" failure and
we shouldn't try to support DT in that case.