Re: [PATCH] gpiolib: Fix incorrect use of find_next_zero_bit()

[Marek Szyprowski]

Hi Janusz,

On 2018-09-29 14:20, Janusz Krzysztofik wrote:
> Commit b17566a6b08b ("gpiolib: Implement fast processing path in
> get/set array"), already fixed to some extent with commit 5d581d7e8cdc
> ("gpiolib: Fix missing updates of bitmap index"), introduced a new mode
> of processing bitmaps where bits applicable for fast bitmap processing
> path are supposed to be skipped while iterating bits which don't apply.
> Unfortunately, find_next_zero_bit() function supposed to skip over
> those fast bits is always called with a 'start' argument equal to an
> index of last zero bit found and returns that index value again an
> again, causing an infinite loop.
>
> Fix it by incrementing the index uncoditionally before
> find_next_zero_bit() is optionally called.
>
> Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Signed-off-by: Janusz Krzysztofik <jmkrzyszt@xxxxxxxxx>

Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

> ---
> Marek,
>
> Could you please test it on top of next-20180920 with "gpiolib: Fix
> missing updates of bitmap index" and optionally "mmc: pwrseq_simple:
> Fix incorrect handling of GPIO bitmap" also applied?

This patch finally fixes the boot issue on Samsung Chromebook Snow.
Thanks!

>
> Thanks,
> Janusz
>
>
>  drivers/gpio/gpiolib.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 6ae13e3e05f1..940b543e966d 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -2878,12 +2878,11 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
>  			int hwgpio = gpio_chip_hwgpio(desc);
>  
>  			__set_bit(hwgpio, mask);
> +			i++;
>  
>  			if (array_info)
>  				i = find_next_zero_bit(array_info->get_mask,
>  						       array_size, i);
> -			else
> -				i++;
>  		} while ((i < array_size) &&
>  			 (desc_array[i]->gdev->chip == chip));
>  
> @@ -2903,12 +2902,11 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
>  				value = !value;
>  			__assign_bit(j, value_bitmap, value);
>  			trace_gpio_value(desc_to_gpio(desc), 1, value);
> +			j++;
>  
>  			if (array_info)
>  				j = find_next_zero_bit(array_info->get_mask, i,
>  						       j);
> -			else
> -				j++;
>  		}
>  
>  		if (mask != fastpath)
> @@ -3191,12 +3189,11 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep,
>  					__clear_bit(hwgpio, bits);
>  				count++;
>  			}
> +			i++;
>  
>  			if (array_info)
>  				i = find_next_zero_bit(array_info->set_mask,
>  						       array_size, i);
> -			else
> -				i++;
>  		} while ((i < array_size) &&
>  			 (desc_array[i]->gdev->chip == chip));
>  		/* push collected bits to outputs */

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