[PATCH] backlight: Delete the OT200 backlight driver
Daniel Thompson
daniel.thompson at linaro.org
Fri Jun 26 11:10:42 UTC 2020
On Fri, Jun 26, 2020 at 12:25:00PM +0200, Linus Walleij wrote:
> This driver has no in-kernel users. The device can only be populated
> by board files since it does not support device tree nor ACPI,
> and nothing in the kernel creates a device named "ot200-backlight".
>
> This driver has been in the kernel since 2012. If it is used by
> out-of-tree code that code should have been upstreamed by now,
> it's been 8 years.
>
> It uses the idiomatic forked GPIO of the CS5535 which combines
> pin control and GPIO into its private custom interface, which
> causes me a headache because that is not how we do things these
> days: we creates separate pin control and GPIO drivers.
>
> Delete this unused driver.
>
> Cc: Christian Gmeiner <christian.gmeiner at gmail.com>
> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
I was curious about this if only because this a driver for an
x86 system and I wondered how the platform device could ever
have been registered.
However I drew a total blank... I can find some tweaks to
coreboot that make this code work better[1] but even after
a careful search of the coreboot code (just in case some
driver I don't know about managed to fetch the
"ot200-backlight" string from the firmware) but I can't find
any code within reach of a search engine (out of tree of not)
that could cause this driver to activate :-(
So, unless we get objections, I've reached the same view
as Linus (and in this post have documented the effort involved):
Reviewed-by: Daniel Thompson <daniel.thompson at linaro.org>
Daniel.
[1]
https://review.coreboot.org/cgit/coreboot.git/commit/?id=4412bc4
> ---
> drivers/video/backlight/Kconfig | 7 --
> drivers/video/backlight/Makefile | 1 -
> drivers/video/backlight/ot200_bl.c | 162 -----------------------------
> 3 files changed, 170 deletions(-)
> delete mode 100644 drivers/video/backlight/ot200_bl.c
>
> diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
> index 7d22d7377606..95c546cc8774 100644
> --- a/drivers/video/backlight/Kconfig
> +++ b/drivers/video/backlight/Kconfig
> @@ -386,13 +386,6 @@ config BACKLIGHT_LP8788
> help
> This supports TI LP8788 backlight driver.
>
> -config BACKLIGHT_OT200
> - tristate "Backlight driver for ot200 visualisation device"
> - depends on CS5535_MFGPT && GPIO_CS5535
> - help
> - To compile this driver as a module, choose M here: the module will be
> - called ot200_bl.
> -
> config BACKLIGHT_PANDORA
> tristate "Backlight driver for Pandora console"
> depends on TWL4030_CORE
> diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
> index 0c1a1524627a..2072d21b60f7 100644
> --- a/drivers/video/backlight/Makefile
> +++ b/drivers/video/backlight/Makefile
> @@ -45,7 +45,6 @@ obj-$(CONFIG_BACKLIGHT_LP8788) += lp8788_bl.o
> obj-$(CONFIG_BACKLIGHT_LV5207LP) += lv5207lp.o
> obj-$(CONFIG_BACKLIGHT_MAX8925) += max8925_bl.o
> obj-$(CONFIG_BACKLIGHT_OMAP1) += omap1_bl.o
> -obj-$(CONFIG_BACKLIGHT_OT200) += ot200_bl.o
> obj-$(CONFIG_BACKLIGHT_PANDORA) += pandora_bl.o
> obj-$(CONFIG_BACKLIGHT_PCF50633) += pcf50633-backlight.o
> obj-$(CONFIG_BACKLIGHT_PWM) += pwm_bl.o
> diff --git a/drivers/video/backlight/ot200_bl.c b/drivers/video/backlight/ot200_bl.c
> deleted file mode 100644
> index 23ee7106c72a..000000000000
> --- a/drivers/video/backlight/ot200_bl.c
> +++ /dev/null
> @@ -1,162 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0-only
> -/*
> - * Copyright (C) 2012 Bachmann electronic GmbH
> - * Christian Gmeiner <christian.gmeiner at gmail.com>
> - *
> - * Backlight driver for ot200 visualisation device from
> - * Bachmann electronic GmbH.
> - */
> -
> -#include <linux/module.h>
> -#include <linux/fb.h>
> -#include <linux/backlight.h>
> -#include <linux/gpio.h>
> -#include <linux/platform_device.h>
> -#include <linux/cs5535.h>
> -
> -static struct cs5535_mfgpt_timer *pwm_timer;
> -
> -/* this array defines the mapping of brightness in % to pwm frequency */
> -static const u8 dim_table[101] = {0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2,
> - 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4,
> - 4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 9,
> - 10, 10, 11, 11, 12, 12, 13, 14, 15, 15, 16,
> - 17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28,
> - 30, 31, 33, 35, 37, 39, 41, 43, 45, 47, 50,
> - 53, 55, 58, 61, 65, 68, 72, 75, 79, 84, 88,
> - 93, 97, 103, 108, 114, 120, 126, 133, 140,
> - 147, 155, 163};
> -
> -struct ot200_backlight_data {
> - int current_brightness;
> -};
> -
> -#define GPIO_DIMM 27
> -#define SCALE 1
> -#define CMP1MODE 0x2 /* compare on GE; output high on compare
> - * greater than or equal */
> -#define PWM_SETUP (SCALE | CMP1MODE << 6 | MFGPT_SETUP_CNTEN)
> -#define MAX_COMP2 163
> -
> -static int ot200_backlight_update_status(struct backlight_device *bl)
> -{
> - struct ot200_backlight_data *data = bl_get_data(bl);
> - int brightness = bl->props.brightness;
> -
> - if (bl->props.state & BL_CORE_FBBLANK)
> - brightness = 0;
> -
> - /* enable or disable PWM timer */
> - if (brightness == 0)
> - cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, 0);
> - else if (data->current_brightness == 0) {
> - cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
> - cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP,
> - MFGPT_SETUP_CNTEN);
> - }
> -
> - /* apply new brightness value */
> - cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,
> - MAX_COMP2 - dim_table[brightness]);
> - data->current_brightness = brightness;
> -
> - return 0;
> -}
> -
> -static int ot200_backlight_get_brightness(struct backlight_device *bl)
> -{
> - struct ot200_backlight_data *data = bl_get_data(bl);
> - return data->current_brightness;
> -}
> -
> -static const struct backlight_ops ot200_backlight_ops = {
> - .update_status = ot200_backlight_update_status,
> - .get_brightness = ot200_backlight_get_brightness,
> -};
> -
> -static int ot200_backlight_probe(struct platform_device *pdev)
> -{
> - struct backlight_device *bl;
> - struct ot200_backlight_data *data;
> - struct backlight_properties props;
> - int retval = 0;
> -
> - /* request gpio */
> - if (devm_gpio_request(&pdev->dev, GPIO_DIMM,
> - "ot200 backlight dimmer") < 0) {
> - dev_err(&pdev->dev, "failed to request GPIO %d\n", GPIO_DIMM);
> - return -ENODEV;
> - }
> -
> - /* request timer */
> - pwm_timer = cs5535_mfgpt_alloc_timer(7, MFGPT_DOMAIN_ANY);
> - if (!pwm_timer) {
> - dev_err(&pdev->dev, "MFGPT 7 not available\n");
> - return -ENODEV;
> - }
> -
> - data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> - if (!data) {
> - retval = -ENOMEM;
> - goto error_devm_kzalloc;
> - }
> -
> - /* setup gpio */
> - cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_ENABLE);
> - cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_AUX1);
> -
> - /* setup timer */
> - cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1, 0);
> - cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP2, MAX_COMP2);
> - cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, PWM_SETUP);
> -
> - data->current_brightness = 100;
> - props.max_brightness = 100;
> - props.brightness = 100;
> - props.type = BACKLIGHT_RAW;
> -
> - bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
> - &pdev->dev, data, &ot200_backlight_ops,
> - &props);
> - if (IS_ERR(bl)) {
> - dev_err(&pdev->dev, "failed to register backlight\n");
> - retval = PTR_ERR(bl);
> - goto error_devm_kzalloc;
> - }
> -
> - platform_set_drvdata(pdev, bl);
> -
> - return 0;
> -
> -error_devm_kzalloc:
> - cs5535_mfgpt_free_timer(pwm_timer);
> - return retval;
> -}
> -
> -static int ot200_backlight_remove(struct platform_device *pdev)
> -{
> - /* on module unload set brightness to 100% */
> - cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
> - cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);
> - cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,
> - MAX_COMP2 - dim_table[100]);
> -
> - cs5535_mfgpt_free_timer(pwm_timer);
> -
> - return 0;
> -}
> -
> -static struct platform_driver ot200_backlight_driver = {
> - .driver = {
> - .name = "ot200-backlight",
> - },
> - .probe = ot200_backlight_probe,
> - .remove = ot200_backlight_remove,
> -};
> -
> -module_platform_driver(ot200_backlight_driver);
> -
> -MODULE_DESCRIPTION("backlight driver for ot200 visualisation device");
> -MODULE_AUTHOR("Christian Gmeiner <christian.gmeiner at gmail.com>");
> -MODULE_LICENSE("GPL");
> -MODULE_ALIAS("platform:ot200-backlight");
> --
> 2.25.4
>
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