Re: [PATCH] mmc: pwrseq_simple: Fix incorrect handling of GPIO bitmap

Marek Szyprowski
2018-09-26T08:14:51Z

Hi Janusz,

On 2018-09-25 21:24, Janusz Krzysztofik wrote:
> Commit b9762bebc633 ("gpiolib: Pass bitmaps, not integer arrays, to
> get/set array") changed the way GPIO values are passed to
> gpiod_get/set_array_value() and friends. The updated code of
> mmc_pwrseq_simple_set_gpios_value() incorrectly uses the 'value'
> argument as a bitmap of GPIO values and assigns it directly to the
> 'values' bitmap variable passed to gpiod_set_array_value_cansleep()
> instead of filling that bitmap with bits equal to the 'value' argument.
> As a result, boot hanging caused by incorrectly handled MMC device
> has been observed.
>
> As a side effect of that incorrect interpreation of the 'value'
> argument, wrong assumption is taken about the 'values' bitmap size
> never exceding the number of bits of the 'value' argument type.
>
> Fix it.
>
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
> ---
> Hi,
>
> I hope I've finally identified the root cause of the boot hang reported
> by Marek Szyprowski. I've reviewed the code of other divers updated for
> the modified GPIO API and found no more issues of that kind.
>
> Marek, can you please test this fix on top of next-20180920 with the fix
> "gpiolib: Fix missing updates of bitmap index" also applied?

Yes, I've just did such test (next-20180920 + "gpiolib: Fix missing
updates of bitmap index" + "mmc: pwrseq_simple: Fix incorrect handling
of GPIO bitmap") and sadly it doesn't fix the boot hang.

With some more debugs in mmc_pwrseq_simple I've noticed that
gpiod_set_array_value_cansleep() never ends and busyloops somewhere.
I'm checking this now.

> I've assumed this fix, if tested successfully, will be merged via GPIO
> tree, hence I've selected Linus as the main recipient of this message.
>
> Thanks,
> Janusz
>
> drivers/mmc/core/pwrseq_simple.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/pwrseq_simple.c b/drivers/mmc/core/pwrseq_simple.c
> index 7f882a2bb872..ece34c734693 100644
> --- a/drivers/mmc/core/pwrseq_simple.c
> +++ b/drivers/mmc/core/pwrseq_simple.c
> @@ -40,13 +40,22 @@ static void mmc_pwrseq_simple_set_gpios_value(struct mmc_pwrseq_simple *pwrseq,
> struct gpio_descs *reset_gpios = pwrseq->reset_gpios;
>
> if (!IS_ERR(reset_gpios)) {
> - DECLARE_BITMAP(values, BITS_PER_TYPE(value));
> + unsigned long *values;
> int nvalues = reset_gpios->ndescs;
>
> - values[0] = value;
> + values = bitmap_alloc(nvalues, GFP_KERNEL);
> + if (!values)
> + return;
> +
> + if (value)
> + bitmap_fill(values, nvalues);
> + else
> + bitmap_zero(values, nvalues);
>
> gpiod_set_array_value_cansleep(nvalues, reset_gpios->desc,
> reset_gpios->info, values);
> +
> + kfree(values);
> }
> }
>

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland