linux-kernel - Re: [PATCH v1 1/1] usb: ulpi: defer ulpi_register on ulpi_read

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Message-ID: <20221110000643.xdoav4c4653x3tjd@synopsys.com>
Date:   Thu, 10 Nov 2022 00:06:54 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Ferry Toth <ftoth@...londelft.nl>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...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>,
        Stephen Boyd <stephen.boyd@...aro.org>,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v1 1/1] usb: ulpi: defer ulpi_register on ulpi_read_id
 timeout

Hi Ferry,

On Wed, Nov 09, 2022, Ferry Toth wrote:
> Since commit 0f010171
> 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. Due to the timeout being masked dwc3 probe continues by
> calling dwc3_core_soft_reset() followed by dwc3_get_extcon() which happens
> to return -EPROBE_DEFER. On deferred probe ulpi_read_id() finally succeeds.
> 
> This patch changes ulpi_read_id() to return -ETIMEDOUT when it occurs and
> catches the error in dwc3_core_init(). It handles the error by calling
> dwc3_core_soft_reset() after which it requests -EPROBE_DEFER. On deferred
> probe ulpi_read_id() again succeeds.
> 
> Signed-off-by: Ferry Toth <ftoth@...londelft.nl>
> ---
>  drivers/usb/common/ulpi.c | 5 +++--
>  drivers/usb/dwc3/core.c   | 5 ++++-
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 

Can you split the dwc3 change and ulpi change to separate patches?

> diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
> index d7c8461976ce..d8f22bc2f9d0 100644
> --- a/drivers/usb/common/ulpi.c
> +++ b/drivers/usb/common/ulpi.c
> @@ -206,8 +206,9 @@ static int ulpi_read_id(struct ulpi *ulpi)
>  
>  	/* Test the interface */
>  	ret = ulpi_write(ulpi, ULPI_SCRATCH, 0xaa);
> -	if (ret < 0)
> -		goto err;
> +	if (ret < 0) {
> +		return ret;
> +	}
>  
>  	ret = ulpi_read(ulpi, ULPI_SCRATCH);
>  	if (ret < 0)
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 648f1c570021..e293ef70039b 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1106,8 +1106,11 @@ static int dwc3_core_init(struct dwc3 *dwc)
>  
>  	if (!dwc->ulpi_ready) {
>  		ret = dwc3_core_ulpi_init(dwc);
> -		if (ret)
> +		if (ret) {
> +			dwc3_core_soft_reset(dwc);

We shouldn't need to do soft reset here. The controller shouldn't be at
a bad/incorrect state at this point to warrant a soft-reset. There will
be a soft-reset when it goes through the initialization again.

> +			ret = -EPROBE_DEFER;

We shouldn't automatically set every error status to correspond to
-EPROBE_DEFER. Check only the approapriate error codes (-ETIMEDOUT +
any other?).

>  			goto err0;
> +		}
>  		dwc->ulpi_ready = true;
>  	}
>  
> -- 
> 2.34.1
> 

Thanks,
Thinh