Date:	Wed, 30 Apr 2014 10:19:49 +0200
From:	Hans de Goede <hdegoede@...hat.com>
To:	Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
	platform-driver-x86@...r.kernel.org
CC:	linux-kernel@...r.kernel.org, matthew.garrett@...ula.com
Subject: Re: [PATCH v2] mba6x_bl: Backlight driver for mid 2013 MacBook Air

Hi,

On 04/29/2014 04:21 PM, Patrik Jakobsson wrote:
> This driver takes control over the LP8550 backlight driver chip found
> in the mid 2013 and newer MacBook Air (6,1 and 6,2). The i915 GPU driver
> cannot properly restore the backlight after resume, but with this driver
> we can hijack the LP8550 and get fully functional backlight support.
> 
> v2: - Dropped "if ACPI" in Kconfig since we already depend on it
>     - Added comment about brightness mapping
>     - Removed lp8550_init() from set_brightness()
>     - Always write to dev_ctl when setting brightness
>     - Change %Ld to standard C %lld
>     - Constify the backlight_ops struct
> 
> Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@...il.com>

Thanks for working on this, looks good:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

Regards,

Hans


> ---
>  MAINTAINERS                     |   6 +
>  drivers/platform/x86/Kconfig    |  13 ++
>  drivers/platform/x86/Makefile   |   1 +
>  drivers/platform/x86/mba6x_bl.c | 353 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 373 insertions(+)
>  create mode 100644 drivers/platform/x86/mba6x_bl.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e67ea24..cad3e82 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5576,6 +5576,12 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next.git
>  S:	Maintained
>  F:	net/mac80211/rc80211_pid*
>  
> +MACBOOK AIR 6,X BACKLIGHT DRIVER
> +M:	Patrik Jakobsson <patrik.r.jakobsson@...il.com>
> +L:	platform-driver-x86@...r.kernel.org
> +S:	Maintained
> +F:	drivers/platform/x86/mba6x_bl.c
> +
>  MACVLAN DRIVER
>  M:	Patrick McHardy <kaber@...sh.net>
>  L:	netdev@...r.kernel.org
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 27df2c5..10ac918 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -795,6 +795,19 @@ config APPLE_GMUX
>  	  graphics as well as the backlight. Currently only backlight
>  	  control is supported by the driver.
>  
> +config MBA6X_BL
> +	tristate "MacBook Air 6,x backlight driver"
> +	depends on ACPI
> +	depends on BACKLIGHT_CLASS_DEVICE
> +	select ACPI_VIDEO
> +	help
> +	 This driver takes control over the LP8550 backlight driver found in
> +	 some MacBook Air models. Say Y here if you have a MacBook Air from mid
> +	 2013 or newer.
> +
> +	 To compile this driver as a module, choose M here: the module will
> +	 be called mba6x_bl.
> +
>  config INTEL_RST
>          tristate "Intel Rapid Start Technology Driver"
>  	depends on ACPI
> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> index 1a2eafc..9a182fe 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -56,3 +56,4 @@ obj-$(CONFIG_INTEL_SMARTCONNECT)	+= intel-smartconnect.o
>  
>  obj-$(CONFIG_PVPANIC)           += pvpanic.o
>  obj-$(CONFIG_ALIENWARE_WMI)	+= alienware-wmi.o
> +obj-$(CONFIG_MBA6X_BL)		+= mba6x_bl.o
> diff --git a/drivers/platform/x86/mba6x_bl.c b/drivers/platform/x86/mba6x_bl.c
> new file mode 100644
> index 0000000..c549667
> --- /dev/null
> +++ b/drivers/platform/x86/mba6x_bl.c
> @@ -0,0 +1,353 @@
> +/*
> + * MacBook Air 6,1 and 6,2 (mid 2013) backlight driver
> + *
> + * Copyright (C) 2014 Patrik Jakobsson (patrik.r.jakobsson@...il.com)
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/backlight.h>
> +#include <linux/acpi.h>
> +#include <acpi/acpi.h>
> +#include <acpi/video.h>
> +
> +#define LP8550_SMBUS_ADDR	(0x58 >> 1)
> +#define LP8550_REG_BRIGHTNESS	0
> +#define LP8550_REG_DEV_CTL	1
> +#define LP8550_REG_FAULT	2
> +#define LP8550_REG_IDENT	3
> +#define LP8550_REG_DIRECT_CTL	4
> +#define LP8550_REG_TEMP_MSB	5 /* Must be read before TEMP_LSB */
> +#define LP8550_REG_TEMP_LSB	6
> +
> +#define INIT_BRIGHTNESS		150
> +
> +static struct {
> +	u8 brightness;	/* Brightness control */
> +	u8 dev_ctl;	/* Device control */
> +	u8 fault;	/* Fault indication */
> +	u8 ident;	/* Identification */
> +	u8 direct_ctl;	/* Direct control */
> +	u8 temp_msb;	/* Temperature MSB  */
> +	u8 temp_lsb;	/* Temperature LSB */
> +} lp8550_regs;
> +
> +static struct platform_device *platform_device;
> +static struct backlight_device *backlight_device;
> +
> +static int lp8550_reg_read(u8 reg, u8 *val)
> +{
> +	acpi_status status;
> +	acpi_handle handle;
> +	struct acpi_object_list arg_list;
> +	struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
> +	union acpi_object args[2];
> +	union acpi_object *result;
> +	int ret = 0;
> +
> +	status = acpi_get_handle(NULL, "\\_SB.PCI0.SBUS.SRDB", &handle);
> +	if (ACPI_FAILURE(status)) {
> +		pr_debug("mba6x_bl: Failed to get acpi handle\n");
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	args[0].type = ACPI_TYPE_INTEGER;
> +	args[0].integer.value = (LP8550_SMBUS_ADDR << 1) | 1;
> +
> +	args[1].type = ACPI_TYPE_INTEGER;
> +	args[1].integer.value = reg;
> +
> +	arg_list.count = 2;
> +	arg_list.pointer = args;
> +
> +	status = acpi_evaluate_object(handle, NULL, &arg_list, &buffer);
> +	if (ACPI_FAILURE(status)) {
> +		pr_debug("mba6x_bl: Failed to read reg: 0x%x\n", reg);
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	result = buffer.pointer;
> +
> +	if (result->type != ACPI_TYPE_INTEGER) {
> +		pr_debug("mba6x_bl: Invalid response in reg: 0x%x (len: %Ld)\n",
> +			 reg, buffer.length);
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	*val = (u8)result->integer.value;
> +out:
> +	kfree(buffer.pointer);
> +	return ret;
> +}
> +
> +static int lp8550_reg_write(u8 reg, u8 val)
> +{
> +	acpi_status status;
> +	acpi_handle handle;
> +	struct acpi_object_list arg_list;
> +	struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
> +	union acpi_object args[3];
> +	union acpi_object *result;
> +	int ret = 0;
> +
> +	status = acpi_get_handle(NULL, "\\_SB.PCI0.SBUS.SWRB", &handle);
> +	if (ACPI_FAILURE(status)) {
> +		pr_debug("mba6x_bl: Failed to get acpi handle\n");
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	args[0].type = ACPI_TYPE_INTEGER;
> +	args[0].integer.value = (LP8550_SMBUS_ADDR << 1) & ~1;
> +
> +	args[1].type = ACPI_TYPE_INTEGER;
> +	args[1].integer.value = reg;
> +
> +	args[2].type = ACPI_TYPE_INTEGER;
> +	args[2].integer.value = val;
> +
> +	arg_list.count = 3;
> +	arg_list.pointer = args;
> +
> +	status = acpi_evaluate_object(handle, NULL, &arg_list, &buffer);
> +	if (ACPI_FAILURE(status)) {
> +		pr_debug("mba6x_bl: Failed to write reg: 0x%x\n", reg);
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	result = buffer.pointer;
> +
> +	if (result->type != ACPI_TYPE_INTEGER || result->integer.value != 1) {
> +		pr_debug("mba6x_bl: Invalid response at reg: 0x%x (len: %lld)\n",
> +			 reg, buffer.length);
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +out:
> +	kfree(buffer.pointer);
> +	return ret;
> +}
> +
> +/*
> + * Map the brightness value to an exponential curve. This makes the perceived
> + * brightness more linear and allows to make better use of the available
> + * brightness range.
> + */
> +static inline int map_brightness(int b)
> +{
> +	return ((b * b + 254) / 255);
> +}
> +
> +static int set_brightness(int brightness)
> +{
> +	int ret;
> +
> +	if (brightness < 0 || brightness > 255)
> +		return -EINVAL;
> +
> +	brightness = map_brightness(brightness);
> +	ret = lp8550_reg_write(LP8550_REG_BRIGHTNESS, (u8)brightness);
> +	if (ret)
> +		return ret;
> +
> +	ret = lp8550_reg_write(LP8550_REG_DEV_CTL, 0x05);
> +	return ret;
> +}
> +
> +static int get_brightness(struct backlight_device *bdev)
> +{
> +	return bdev->props.brightness;
> +}
> +
> +static int update_status(struct backlight_device *bdev)
> +{
> +	return set_brightness(bdev->props.brightness);
> +}
> +
> +static int lp8550_probe(void)
> +{
> +	u8 val;
> +	int ret;
> +
> +	ret = lp8550_reg_read(LP8550_REG_IDENT, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val != 0xfc)
> +		return -ENODEV;
> +
> +	pr_info("mba6x_bl: Found LP8550 backlight driver\n");
> +	return 0;
> +}
> +
> +static int lp8550_save(void)
> +{
> +	int ret;
> +
> +	ret = lp8550_reg_read(LP8550_REG_DEV_CTL, &lp8550_regs.dev_ctl);
> +	if (ret)
> +		return ret;
> +
> +	ret = lp8550_reg_read(LP8550_REG_BRIGHTNESS, &lp8550_regs.brightness);
> +	return ret;
> +}
> +
> +
> +static int lp8550_restore(void)
> +{
> +	int ret;
> +
> +	ret = lp8550_reg_write(LP8550_REG_BRIGHTNESS, lp8550_regs.brightness);
> +	if (ret)
> +		return ret;
> +
> +	ret = lp8550_reg_write(LP8550_REG_DEV_CTL, lp8550_regs.dev_ctl);
> +	return ret;
> +}
> +
> +static int lp8550_init(void)
> +{
> +	int ret, i;
> +
> +	for (i = 0; i < 10; i++) {
> +		ret = lp8550_reg_write(LP8550_REG_BRIGHTNESS, INIT_BRIGHTNESS);
> +		if (!ret)
> +			break;
> +	}
> +
> +	if (i > 0)
> +		pr_err("mba6x_bl: Init retries: %d\n", i);
> +
> +	if (ret)
> +		return ret;
> +
> +	ret = lp8550_reg_write(LP8550_REG_DEV_CTL, 0x05);
> +	return ret;
> +}
> +
> +static const struct backlight_ops backlight_ops = {
> +	.update_status = update_status,
> +	.get_brightness = get_brightness,
> +};
> +
> +static struct platform_driver drv;
> +
> +static int platform_probe(struct platform_device *dev)
> +{
> +	struct backlight_properties props;
> +	int ret;
> +
> +	ret = lp8550_probe();
> +	if (ret)
> +		return ret;
> +
> +	ret = lp8550_save();
> +	if (ret)
> +		return ret;
> +
> +	ret = lp8550_init();
> +	if (ret)
> +		return ret;
> +
> +	memset(&props, 0, sizeof(struct backlight_properties));
> +	props.max_brightness = 255;
> +	props.brightness = INIT_BRIGHTNESS;
> +	props.type = BACKLIGHT_FIRMWARE;
> +
> +	backlight_device = backlight_device_register("mba6x_backlight",
> +						     NULL, NULL,
> +						     &backlight_ops, &props);
> +	if (IS_ERR(backlight_device)) {
> +		pr_err("mba6x_bl: Failed to register backlight device\n");
> +		return PTR_ERR(backlight_device);
> +	}
> +
> +	acpi_video_dmi_promote_vendor();
> +	acpi_video_unregister();
> +
> +	backlight_update_status(backlight_device);
> +
> +	return 0;
> +}
> +
> +static int platform_remove(struct platform_device *dev)
> +{
> +	backlight_device_unregister(backlight_device);
> +	lp8550_restore();
> +	pr_info("mba6x_bl: Restored old configuration\n");
> +
> +	return 0;
> +}
> +
> +static int platform_resume(struct platform_device *dev)
> +{
> +	/*
> +	 * Firmware restores the LP8550 for us but we might need some tweaking
> +	 * in the future if firmware behaviour is changed.
> +	 */
> +	return 0;
> +}
> +
> +static void platform_shutdown(struct platform_device *dev)
> +{
> +	/* We must restore or screen might go black on reboot */
> +	lp8550_restore();
> +}
> +
> +static struct platform_driver drv = {
> +	.probe		= platform_probe,
> +	.remove		= platform_remove,
> +	.resume		= platform_resume,
> +	.shutdown	= platform_shutdown,
> +	.driver	= {
> +		.name = "mba6x_bl",
> +		.owner = THIS_MODULE,
> +	},
> +};
> +
> +static int __init mba6x_bl_init(void)
> +{
> +	int ret;
> +
> +	ret = platform_driver_register(&drv);
> +	if (ret) {
> +		pr_err("Failed to register platform driver\n");
> +		return ret;
> +	}
> +
> +	platform_device = platform_device_register_simple("mba6x_bl", -1, NULL,
> +							  0);
> +	return 0;
> +}
> +
> +static void __exit mba6x_bl_exit(void)
> +{
> +	platform_device_unregister(platform_device);
> +	platform_driver_unregister(&drv);
> +}
> +
> +module_init(mba6x_bl_init);
> +module_exit(mba6x_bl_exit);
> +
> +MODULE_AUTHOR("Patrik Jakobsson <patrik.r.jakobsson@...il.com>");
> +MODULE_DESCRIPTION("MacBook Air 6,1 and 6,2 backlight driver");
> +MODULE_LICENSE("GPL");
> +
> +MODULE_ALIAS("dmi:*:pnMacBookAir6*");
> 
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