Re: [PATCH v7 4/4] gpiolib: Implement fast processing path in get/set array

Janusz Krzysztofik
2018-09-20T15:47:04Z

On Thursday, September 20, 2018 12:11:48 PM CEST Marek Szyprowski wrote:
> Hi All,
>
> On 2018-09-02 14:01, Janusz Krzysztofik wrote:
> > Certain GPIO descriptor arrays returned by gpio_get_array() may contain
> > information on direct mapping of array members to pins of a single GPIO
> > chip in hardware order. In such cases, bitmaps of values can be passed
> > directly from/to the chip's .get/set_multiple() callbacks without
> > wasting time on iterations.
> >
> > Add respective code to gpiod_get/set_array_bitmap_complex() functions.
> > Pins not applicable for fast path are processed as before, skipping
> > over the 'fast' ones.
> >
> > Cc: Jonathan Corbet <corbet@lwn.net>
> > Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
>
> I've just noticed that this patch landed in today's linux-next. Sadly it
> breaks booting of Exynos5250-based Samsung Snow Chromebook (ARM 32bit,
> device-tree source arch/arm/boot/dts/exynos5250-snow.dts).
>
> Booting hangs after detecting MMC cards. Reverting this patch fixes the
> boot. I will try later to add some debugs and investigate it further what
> really happens when booting hangs.

Hi Marek,

Thanks for reporting. Could you please try the following fix?

Thanks,
Janusz

From d7ecd435bfb4972766b63ac383a43875700c7452 Mon Sep 17 00:00:00 2001
From: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Date: Thu, 20 Sep 2018 17:37:21 +0200
Subject: [PATCH] gpiolib: Fix bitmap index not updated

While skipping fast path bits, bitmap index is not updated with next
found zero bit position. Fix it.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
---
drivers/gpio/gpiolib.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index a53d17745d21..5bc3447949c9 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2880,7 +2880,7 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
__set_bit(hwgpio, mask);

if (array_info)
- find_next_zero_bit(array_info->get_mask,
+ i = find_next_zero_bit(array_info->get_mask,
array_size, i);
else
i++;
@@ -2905,7 +2905,8 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
trace_gpio_value(desc_to_gpio(desc), 1, value);

if (array_info)
- find_next_zero_bit(array_info->get_mask, i, j);
+ i = find_next_zero_bit(array_info->get_mask, i,
+ j);
else
j++;
}
@@ -3192,7 +3193,7 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep,
}

if (array_info)
- find_next_zero_bit(array_info->set_mask,
+ i = find_next_zero_bit(array_info->set_mask,
array_size, i);
else
i++;
--
2.16.4