[PATCH 1/1] apple-gmux: Hard Code max brightness for MMIO gmux

[PATCH 1/1] apple-gmux: Hard Code max brightness for MMIO gmux

[Orlando Chamberlain]

The data in the max brightness port for iMacs with MMIO gmux incorrectly
reports 0x03ff, but it should be 0xffff. As all other MMIO gmux models
have 0xffff, hard code this for all MMIO gmux's so they all have the
proper brightness range accessible.

Reported-by: Karsten Leipold <poldi@dfn.de>
Signed-off-by: Orlando Chamberlain <orlandoch.dev@gmail.com>
---
 drivers/platform/x86/apple-gmux.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index cadbb557a108..1417e230edbd 100644
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -105,6 +105,8 @@ struct apple_gmux_config {
 #define GMUX_BRIGHTNESS_MASK		0x00ffffff
 #define GMUX_MAX_BRIGHTNESS		GMUX_BRIGHTNESS_MASK
 
+# define MMIO_GMUX_MAX_BRIGHTNESS	0xffff
+
 static u8 gmux_pio_read8(struct apple_gmux_data *gmux_data, int port)
 {
 	return inb(gmux_data->iostart + port);
@@ -857,7 +859,17 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
 
 	memset(&props, 0, sizeof(props));
 	props.type = BACKLIGHT_PLATFORM;
-	props.max_brightness = gmux_read32(gmux_data, GMUX_PORT_MAX_BRIGHTNESS);
+
+	/*
+	 * All MMIO gmux's have 0xffff as max brightness, but some iMacs incorrectly
+	 * report 0x03ff, despite the firmware being happy to set 0xffff as the brightness
+	 * at boot. Force 0xffff for all MMIO gmux's so they all have the correct brightness
+	 * range.
+	 */
+	if (type == APPLE_GMUX_TYPE_MMIO)
+		props.max_brightness = MMIO_GMUX_MAX_BRIGHTNESS;
+	else
+		props.max_brightness = gmux_read32(gmux_data, GMUX_PORT_MAX_BRIGHTNESS);
 
 #if IS_REACHABLE(CONFIG_ACPI_VIDEO)
 	register_bdev = acpi_video_get_backlight_type() == acpi_backlight_apple_gmux;
-- 
2.42.0

Re: [PATCH 1/1] apple-gmux: Hard Code max brightness for MMIO gmux

[Hans de Goede]

Hi,

On 10/17/23 13:14, Orlando Chamberlain wrote:
> The data in the max brightness port for iMacs with MMIO gmux incorrectly
> reports 0x03ff, but it should be 0xffff. As all other MMIO gmux models
> have 0xffff, hard code this for all MMIO gmux's so they all have the
> proper brightness range accessible.
> 
> Reported-by: Karsten Leipold <poldi@dfn.de>
> Signed-off-by: Orlando Chamberlain <orlandoch.dev@gmail.com>

Thank you for your patch/series, I've applied this patch
(series) to the pdx86 fixes branch:
https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=fixes

I have added the following Fixes: tag while merging this:

Fixes: 0c18184de990 ("platform/x86: apple-gmux: support MMIO gmux on T2 Macs")

I will include this patch in my next fixes pull-req to Linus
for the current kernel development cycle.

Regards,

Hans



> ---
>  drivers/platform/x86/apple-gmux.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
> index cadbb557a108..1417e230edbd 100644
> --- a/drivers/platform/x86/apple-gmux.c
> +++ b/drivers/platform/x86/apple-gmux.c
> @@ -105,6 +105,8 @@ struct apple_gmux_config {
>  #define GMUX_BRIGHTNESS_MASK		0x00ffffff
>  #define GMUX_MAX_BRIGHTNESS		GMUX_BRIGHTNESS_MASK
>  
> +# define MMIO_GMUX_MAX_BRIGHTNESS	0xffff
> +
>  static u8 gmux_pio_read8(struct apple_gmux_data *gmux_data, int port)
>  {
>  	return inb(gmux_data->iostart + port);
> @@ -857,7 +859,17 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
>  
>  	memset(&props, 0, sizeof(props));
>  	props.type = BACKLIGHT_PLATFORM;
> -	props.max_brightness = gmux_read32(gmux_data, GMUX_PORT_MAX_BRIGHTNESS);
> +
> +	/*
> +	 * All MMIO gmux's have 0xffff as max brightness, but some iMacs incorrectly
> +	 * report 0x03ff, despite the firmware being happy to set 0xffff as the brightness
> +	 * at boot. Force 0xffff for all MMIO gmux's so they all have the correct brightness
> +	 * range.
> +	 */
> +	if (type == APPLE_GMUX_TYPE_MMIO)
> +		props.max_brightness = MMIO_GMUX_MAX_BRIGHTNESS;
> +	else
> +		props.max_brightness = gmux_read32(gmux_data, GMUX_PORT_MAX_BRIGHTNESS);
>  
>  #if IS_REACHABLE(CONFIG_ACPI_VIDEO)
>  	register_bdev = acpi_video_get_backlight_type() == acpi_backlight_apple_gmux;