linux-kernel - Re: [BUG] SPI broken for SPI based panel drivers

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Message-Id: <4AC29229-9542-4E77-B993-217E29C7E209@goldelico.com>
Date:   Tue, 1 Dec 2020 09:59:43 +0100
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Sven Van Asbroeck <thesven73@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>
Subject: Re: [BUG] SPI broken for SPI based panel drivers

Hi Sven,

> Am 30.11.2020 um 21:13 schrieb Sven Van Asbroeck <thesven73@...il.com>:
> 
> Hi Nikolaus, thank you for reaching out !
> 
> On Mon, Nov 30, 2020 at 2:06 PM H. Nikolaus Schaller <hns@...delico.com> wrote:
>> 
>> But reverting your patch brings back the display. So it appears as if it does not
>> fix a breakage, rather breaks a previously working setup.
> 
> The patch in question fixes an important breakage: before the patch, literally
> hundreds of SPI drivers no longer worked - only if the SPI bus master
> driver was using gpio descriptors.
> 
> We knew that there was a chance that our fix would break something else.
> But hopefully "it fixes more than it breaks"

Then it should not have been applied to mainline but fully worked out and tested.

> 
>> 
>> What should we do?
>> 
> 
> Can you try the following patch ?

Unfortunately it doesn't seem to fix it. And combined with the second proposed fix also not.

BR and thanks,
Nikolaus

my combined change:

diff --git a/drivers/spi/spi-gpio.c b/drivers/spi/spi-gpio.c
index 7ceb0ba27b755c..ec2da62716a279 100644
--- a/drivers/spi/spi-gpio.c
+++ b/drivers/spi/spi-gpio.c
@@ -208,8 +208,8 @@ static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
        if (spi_gpio->cs_gpios) {
                struct gpio_desc *cs = spi_gpio->cs_gpios[spi->chip_select];
 
-               /* SPI chip selects are normally active-low */
-               gpiod_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
+               /* SPI chip select polarity handled by gpiolib*/
+               gpiod_set_value_cansleep(cs, is_active);
        }
 }
 
@@ -226,8 +226,7 @@ static int spi_gpio_setup(struct spi_device *spi)
        if (spi_gpio->cs_gpios) {
                cs = spi_gpio->cs_gpios[spi->chip_select];
                if (!spi->controller_state && cs)
-                       status = gpiod_direction_output(cs,
-                                                 !(spi->mode & SPI_CS_HIGH));
+                       status = gpiod_direction_output(cs, false);
        }
 
        if (!status)