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

[Ludovic BARRE]

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@xxxxxxx>
> > ---
> > 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);