linux-kernel - Re: [PATCH v4 1/2] usb: ulpi: defer ulpi_register on ulpi_read

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Date:   Mon, 21 Nov 2022 10:35:54 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Ferry Toth <ftoth@...londelft.nl>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Sean Anderson <sean.anderson@...o.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Ferry Toth <fntoth@...il.com>,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH v4 1/2] usb: ulpi: defer ulpi_register on ulpi_read_id
 timeout

Sorry, Ferry, but a few style issues in the commit message.

On Sun, Nov 20, 2022 at 04:37:03PM +0100, Ferry Toth wrote:
> Since commit 0f0101719138 ("usb: dwc3: Don't switch OTG -> peripheral if extcon is present")

It's fine to wrap this long line when it's in the commit message main body.

> Dual Role support on Intel Merrifield platform broke due to rearranging
> the call to dwc3_get_extcon().
> 
> It appears to be caused by ulpi_read_id() on the first test write failing
> with -ETIMEDOUT. Currently ulpi_read_id() expects to discover the phy via
> DT when the test write fails and returns 0 in that case, even if DT does not
> provide the phy. As a result usb probe completes without phy.
> 
> On Intel Merrifield the issue is reproducible but difficult to find the
> root cause. Using an ordinary kernel and rootfs with buildroot ulpi_read_id()
> succeeds. As soon as adding ftrace / bootconfig to find out why,
> ulpi_read_id() fails and we can't analyze the flow. Using another rootfs
> ulpi_read_id() fails even without adding ftrace. Appearantly the issue is
> some kind of timing / race, but merely retrying ulpi_read_id() does not
> resolve the issue.

> This patch makes ulpi_read_id() return -ETIMEDOUT to its user if the first

s/This patch makes/Make/  (as per Submitting Patches: use imperative form)

> test write fails. The user should then handle it appropriately. A follow up
> patch will make dwc3_core_init() set -EPROBE_DEFER in this case and bail out.
> 
> Fixes: ef6a7bcfb01c ("usb: ulpi: Support device discovery via DT")
> Cc: stable@...r.kernel.org

> 

This line breaks the tag block, meaning that Fixes won't be recognized as a tag
by some scripts.

> Signed-off-by: Ferry Toth <ftoth@...londelft.nl>
> ---
>  drivers/usb/common/ulpi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
> index d7c8461976ce..60e8174686a1 100644
> --- a/drivers/usb/common/ulpi.c
> +++ b/drivers/usb/common/ulpi.c
> @@ -207,7 +207,7 @@ static int ulpi_read_id(struct ulpi *ulpi)
>  	/* Test the interface */
>  	ret = ulpi_write(ulpi, ULPI_SCRATCH, 0xaa);
>  	if (ret < 0)
> -		goto err;
> +		return ret;
>  
>  	ret = ulpi_read(ulpi, ULPI_SCRATCH);
>  	if (ret < 0)
> -- 
> 2.37.2
> 

-- 
With Best Regards,
Andy Shevchenko