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

On Thursday, September 20, 2018 12:11:48 PM CEST Marek Szyprowski wrote:

Hi All,

On 2018-09-02 14:01, Janusz Krzysztofik wrote:

quoted

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