linux-kernel - Re: [RFC PATCH] mtd: spi-nor: handle signal case as failure

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Message-ID: <845ce78f-f3b0-35c0-8e3d-580ce4e1f63a@st.com>
Date:   Thu, 4 May 2017 09:40:11 +0200
From:   Ludovic BARRE <ludovic.barre@...com>
To:     Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Nicholas Mc Guire <der.herr@...r.at>
CC:     Marek Vasut <marek.vasut@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Richard Weinberger <richard@....at>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] mtd: spi-nor: handle signal case as failure

On 05/03/2017 11:23 PM, Cyrille Pitchen wrote:
> Hi all,
>
> Le 03/05/2017 à 11:53, Nicholas Mc Guire a écrit :
>>   The problem is that stm32_qspi_wait_cmd() will indicate success in case of
>>   being interrupted. The if condition is incomplete here as
>>   wait_for_copletion_interruptible_timeout can return -ERESTARTSYS but this
>>   is not handled by if(!wait_for_completion_interruptible_timeout()).
>>   While somewhat unlikely it probably would be hard to figure out what went
>>   wrong if the signal case does occur.
>>
>> Fixes: commit 0d43d7ab277a ("mtd: spi-nor: add driver for STM32 quad spi flash controller")
>> Signed-off-by: Nicholas Mc Guire <der.herr@...r.at>
>> ---
>> Problem found by experimental coccinelle script
>>
>> Its not clear if its sufficient to simply treat this case as failure or
>> if it might need some debug output to allow differentiation of signal
>> and timeout case.
>>
>> Patch was compile tested with: stm32_defconfig +CONFIG_MTD=y, CONFIG_MTD_SPI_NOR=y,
>> CONFIG_SPI_STM32_QUADSPI=m
>>
>> Patch is against v4.11-rc8 (localversion-next is next-20170503)
>>
>>   drivers/mtd/spi-nor/stm32-quadspi.c  | 10 ++++++++--
>>   1 files changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/stm32-quadspi.c b/drivers/mtd/spi-nor/stm32-quadspi.c
>> index 1056e74..27147ad 100644
>> --- a/drivers/mtd/spi-nor/stm32-quadspi.c
>> +++ b/drivers/mtd/spi-nor/stm32-quadspi.c
>> @@ -159,6 +159,7 @@ static int stm32_qspi_wait_cmd(struct stm32_qspi *qspi)
>>   {
>>   	u32 cr;
>>   	int err = 0;
>> +	long timeout = 0;
>>   
>>   	if (readl_relaxed(qspi->io_base + QUADSPI_SR) & SR_TCF)
>>   		return 0;
>> @@ -167,8 +168,13 @@ static int stm32_qspi_wait_cmd(struct stm32_qspi *qspi)
>>   	cr = readl_relaxed(qspi->io_base + QUADSPI_CR);
>>   	writel_relaxed(cr | CR_TCIE, qspi->io_base + QUADSPI_CR);
>>   
>> -	if (!wait_for_completion_interruptible_timeout(&qspi->cmd_completion,
>> -						       msecs_to_jiffies(1000)))
> Ludovic, can we just use wait_for_completion_timeout() instead?
exactly, I would use _interruptible extension to allow "user" to
abort a long transfer (without wait the end of command transfert).
But it's not crucial for stm32_qspi, this could be replace by
wait_for_completion_timeout.
sorry to disturb the "mtd pull" :-(

Best regards,
Ludo
> I think so but you surely know better than me :)
> Do you plan to receive signal? maybe to abort the current SPI flash command?
>
> Best regards,
>
> Cyrille
>
>> +	timeout = wait_for_completion_interruptible_timeout(
>> +				&qspi->cmd_completion, msecs_to_jiffies(1000));
>> +
>> +	/* since the calling side only cares about success of failure
>> +	 * returning -ETIMEDOUT even when interrupted should be ok here
>> +	 */
>> +	if (timeout == 0 || timeout == -ERESTARTSYS)
>>   		err = -ETIMEDOUT;
>>   
>>   	writel_relaxed(cr, qspi->io_base + QUADSPI_CR);
>>