linux-kernel - Re: [PATCH v4 1/4] Input: ads7846

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Date:   Sun, 4 Jun 2023 17:44:39 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Janusz Krzysztofik <jmkrzyszt@...il.com>,
        Tony Lindgren <tony@...mide.com>,
        Russell King <linux@...linux.org.uk>,
        Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Andreas Kemnade <andreas@...nade.info>,
        Helge Deller <deller@....de>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-input@...r.kernel.org, linux-spi@...r.kernel.org,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-mmc@...r.kernel.org
Subject: Re: [PATCH v4 1/4] Input: ads7846 - Convert to use software nodes

Le 08/05/2023 à 23:20, Linus Walleij a écrit :
> The Nokia 770 is using GPIOs from the global numberspace on the
> CBUS node to pass down to the LCD controller. This regresses when we
> let the OMAP GPIO driver use dynamic GPIO base.
> 
> The Nokia 770 now has dynamic allocation of IRQ numbers, so this
> needs to be fixed for it to work.
> 
> As this is the only user of LCD MIPID we can easily augment the
> driver to use a GPIO descriptor instead and resolve the issue.
> 
> The platform data .shutdown() callback wasn't even used in the
> code, but we encode a shutdown asserting RESET in the remove()
> callback for completeness sake.
> 
> The CBUS also has the ADS7846 touchscreen attached.
> 
> Populate the devices on the Nokia 770 CBUS I2C using software
> nodes instead of platform data quirks. This includes the LCD
> and the ADS7846 touchscreen so the conversion just brings the LCD
> along with it as software nodes is an all-or-nothing design
> pattern.
> 
> The ADS7846 has some limited support for using GPIO descriptors,
> let's convert it over completely to using device properties and then
> fix all remaining boardfile users to provide all platform data using
> software nodes.
> 
> Dump the of includes and of_match_ptr() in the ADS7846 driver as part
> of the job.
> 
> Since we have to move ADS7846 over to obtaining the GPIOs it is
> using exclusively from descriptors, we provide descriptor tables
> for the two remaining in-kernel boardfiles using ADS7846:
> 
> - PXA Spitz
> - MIPS Alchemy DB1000 development board
> 
> It was too hard for me to include software node conversion of
> these two remaining users at this time: the spitz is using a
> hscync callback in the platform data that would require further
> GPIO descriptor conversion of the Spitz, and moving the hsync
> callback down into the driver: it will just become too big of
> a job, but it can be done separately.
> 
> The MIPS Alchemy DB1000 is simply something I cannot test, so take
> the easier approach of just providing some GPIO descriptors in
> this case as I don't want the patch to grow too intrusive.
> 
> As we see that several device trees have incorrect polarity flags
> and just expect to bypass the gpiolib polarity handling, fix up
> all device trees too, in a separate patch.
> 
> Suggested-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> Fixes: 92bf78b33b0b ("gpio: omap: use dynamic allocation of base")
> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
> ---

[...]

> diff --git a/drivers/video/fbdev/omap/lcd_mipid.c b/drivers/video/fbdev/omap/lcd_mipid.c
> index 03cff39d392d..e4a7f0b824ff 100644
> --- a/drivers/video/fbdev/omap/lcd_mipid.c
> +++ b/drivers/video/fbdev/omap/lcd_mipid.c
> @@ -7,6 +7,7 @@
>    */
>   #include <linux/device.h>
>   #include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
>   #include <linux/slab.h>
>   #include <linux/workqueue.h>
>   #include <linux/spi/spi.h>
> @@ -41,6 +42,7 @@ struct mipid_device {
>   						   when we can issue the
>   						   next sleep in/out command */
>   	unsigned long	hw_guard_wait;		/* max guard time in jiffies */
> +	struct gpio_desc	*reset;
>   
>   	struct omapfb_device	*fbdev;
>   	struct spi_device	*spi;
> @@ -556,6 +558,12 @@ static int mipid_spi_probe(struct spi_device *spi)
>   		return -ENOMEM;
>   	}
>   
> +	/* This will de-assert RESET if active */
> +	md->reset = gpiod_get(&spi->dev, "reset", GPIOD_OUT_LOW);
> +	if (IS_ERR(md->reset))
> +		return dev_err_probe(&spi->dev, PTR_ERR(md->reset),
> +				     "no reset GPIO line\n");
> +
>   	spi->mode = SPI_MODE_0;
>   	md->spi = spi;
>   	dev_set_drvdata(&spi->dev, md);
> @@ -574,6 +582,8 @@ static void mipid_spi_remove(struct spi_device *spi)
>   {
>   	struct mipid_device *md = dev_get_drvdata(&spi->dev);
>   
> +	/* Asserts RESET */
> +	gpiod_set_value(md->reset, 1);

Hi,

should this also be done in the probe if mipid_detect() fails?

If yes, please also look at [1], that I've just sent, which introduces 
an error handling path in the probe.

CJ

[1]: 
https://lore.kernel.org/all/8b82e34724755b69f34f15dddb288cd373080390.1620505229.git.christophe.jaillet@wanadoo.fr/

>   	mipid_disable(&md->panel);
>   	kfree(md);
>   }

[...]