Hi
The platform-driver-x86 maintainers should've probably been
CCd. You may or may not know, but the `scripts/get_maintainers.pl`
script can be used to determine the appropriate recipients.
2022. március 16., szerda 2:25 keltezéssel, Daniel Dadap írta:
> Some notebook systems with EC-driven backlight control appear to have a
> firmware bug which causes the system to use GPU-driven backlight control
> upon a fresh boot, but then switches to EC-driven backlight control
> after completing a suspend/resume cycle. All the while, the firmware
> reports that the backlight is under EC control, regardless of what is
> actually controlling the backlight brightness.
>
> This leads to the following behavior:
>
> * nvidia-wmi-ec-backlight gets probed on a fresh boot, due to the
> WMI-wrapped ACPI method erroneously reporting EC control.
> * nvidia-wmi-ec-backlight does not work until after a suspend/resume
> cycle, due to the backlight control actually being GPU-driven.
> * GPU drivers also register their own backlight handlers: in the case
> of the notebook system where this behavior has been observed, both
> amdgpu and the NVIDIA proprietary driver register backlight handlers.
> * The GPU which has backlight control upon a fresh boot (amdgpu in the
> case observed so far) can successfully control the backlight through
> its backlight driver's sysfs interface, but stops working after the
> first suspend/resume cycle.
> * nvidia-wmi-ec-backlight is unable to control the backlight upon a
> fresh boot, but begins to work after the first suspend/resume cycle.
> * The GPU which does not have backlight control (NVIDIA in this case)
> is not able to control the backlight at any point while the system
> is in operation. On similar hybrid systems with an EC-controlled
> backlight, and AMD/NVIDIA iGPU/dGPU, the NVIDIA proprietary driver
> does not register its backlight handler. It has not been determined
> whether the non-functional handler registered by the NVIDIA driver
> is due to another firmware bug, or a bug in the NVIDIA driver.
>
> Since nvidia-wmi-ec-backlight registers as a BACKLIGHT_FIRMWARE type
> device, it takes precedence over the BACKLIGHT_RAW devices registered
> by the GPU drivers. This in turn leads to backlight control appearing
> to be non-functional until after completing a suspend/resume cycle.
> However, it is still possible to control the backlight through direct
> interaction with the working GPU driver's backlight sysfs interface.
>
> These systems also appear to have a second firmware bug which resets
> the EC's brightness level to 100% on resume, but leaves the state in
> the kernel at the pre-suspend level. This causes attempts to save
> and restore the backlight level across the suspend/resume cycle to
> fail, due to the level appearing not to change even though it did.
>
> In order to work around these issue, add quirk tables to detect
> systems that are known to show these behaviors. So far, there is
> only one known system that requires these workarounds, and both
> issues are present on that system, but the quirks are tracked in
> separate tables to make it easier to add them to other systems which
> may exhibit one of the bugs, but not the other. The original systems
> that this driver was tested on during development do not exhibit
> either of these quirks.
>
> If a system with the "GPU driver has backlight control" quirk is
> detected, nvidia-wmi-ec-backlight will grab a reference to the working
> (when freshly booted) GPU backlight handler and relays any backlight
> brightness level change requests directed at the EC to also be applied
> to the GPU backlight interface. This leads to redundant updates
> directed at the GPU backlight driver after a suspend/resume cycle, but
> it does allow the EC backlight control to work when the system is
> freshly booted.
>
> If a system with the "backlight level reset to full on resume" quirk
> is detected, nvidia-wmi-ec-backlight will register a PM notifier to
> reset the backlight to the previous level upon resume.
>
> These workarounds are also plumbed through to kernel module parameters,
> to make it easier for users who suspect they may be affected by one or
> both of these bugs to test whether these workarounds are effective on
> their systems as well.
>
> Signed-off-by: Daniel Dadap <ddadap@xxxxxxxxxx>
> Tested-by: Alexandru Dinu <alex.dinu07@xxxxxxxxx>
> ---
> .../platform/x86/nvidia-wmi-ec-backlight.c | 181 +++++++++++++++++-
> 1 file changed, 179 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/platform/x86/nvidia-wmi-ec-backlight.c b/drivers/platform/x86/nvidia-wmi-ec-backlight.c
> index 61e37194df70..ccb3b506c12c 100644
> --- a/drivers/platform/x86/nvidia-wmi-ec-backlight.c
> +++ b/drivers/platform/x86/nvidia-wmi-ec-backlight.c
> @@ -3,8 +3,11 @@
> * Copyright (c) 2020, NVIDIA CORPORATION. All rights reserved.
> */
>
> +#define pr_fmt(f) "%s: " f "\n", KBUILD_MODNAME
`KBUILD_MODNAME` is a string literal, so you can do e.g.
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> #include <linux/acpi.h>
> #include <linux/backlight.h>
> +#include <linux/dmi.h>
> #include <linux/mod_devicetable.h>
> #include <linux/module.h>
> #include <linux/types.h>
> @@ -75,6 +78,69 @@ struct wmi_brightness_args {
> u32 ignored[3];
> };
>
> +/**
> + * struct nvidia_wmi_ec_backlight_priv - driver private data
> + * @bl_dev: the associated backlight device
> + * @proxy_target: backlight device which receives relayed brightness changes
> + * @notifier: notifier block for resume callback
> + */
> +struct nvidia_wmi_ec_backlight_priv {
> + struct backlight_device *bl_dev;
> + struct backlight_device *proxy_target;
> + struct notifier_block nb;
> +};
> +
> +static char *backlight_proxy_target;
> +module_param(backlight_proxy_target, charp, 0);
It seems these module parameters are neither readable nor writable,
is that intentional?
> +MODULE_PARM_DESC(backlight_proxy_target, "Relay brightness change requests to the named backlight driver, on systems which erroneously report EC backlight control.");
> +
> +static int max_reprobe_attempts = 128;
Can you elaborate how this number was arrived at?
> +module_param(max_reprobe_attempts, int, 0);
> +MODULE_PARM_DESC(max_reprobe_attempts, "Limit of reprobe attempts when relaying brightness change requests.");
> +
> +static bool restore_level_on_resume;
> +module_param(restore_level_on_resume, bool, 0);
> +MODULE_PARM_DESC(restore_level_on_resume, "Restore the backlight level when resuming from suspend, on systems which reset the EC's backlight level on resume.");
> +
> +static int assign_relay_quirk(const struct dmi_system_id *id)
> +{
> + backlight_proxy_target = id->driver_data;
> + return true;
> +}
> +
> +#define PROXY_QUIRK_ENTRY(vendor, product, quirk_data) { \
> + .callback = assign_relay_quirk, \
> + .matches = { \
> + DMI_MATCH(DMI_SYS_VENDOR, vendor), \
> + DMI_MATCH(DMI_PRODUCT_VERSION, product) \
> + }, \
> + .driver_data = quirk_data \
> +}
> +
> +static const struct dmi_system_id proxy_quirk_table[] = {
> + PROXY_QUIRK_ENTRY("LENOVO", "Legion S7 15ACH6", "amdgpu_bl1"),
> + { }
> +};
> +
> +static int assign_restore_quirk(const struct dmi_system_id *id)
> +{
> + restore_level_on_resume = true;
> + return true;
> +}
> +
> +#define RESTORE_QUIRK_ENTRY(vendor, product) { \
> + .callback = assign_restore_quirk, \
> + .matches = { \
> + DMI_MATCH(DMI_SYS_VENDOR, vendor), \
> + DMI_MATCH(DMI_PRODUCT_VERSION, product), \
> + } \
> +}
> +
> +static const struct dmi_system_id restore_quirk_table[] = {
> + RESTORE_QUIRK_ENTRY("LENOVO", "Legion S7 15ACH6"),
> + { }
> +};
> +
> /**
> * wmi_brightness_notify() - helper function for calling WMI-wrapped ACPI method
> * @w: Pointer to the struct wmi_device identified by %WMI_BRIGHTNESS_GUID
> @@ -119,9 +185,30 @@ static int wmi_brightness_notify(struct wmi_device *w, enum wmi_brightness_metho
> return 0;
> }
>
> +static int scale_backlight_level(struct backlight_device *a,
> + struct backlight_device *b)
> +{
> + /* because floating point math in the kernel is annoying */
> + const int scaling_factor = 65536;
> + int level = a->props.brightness;
> + int relative_level = level * scaling_factor / a->props.max_brightness;
> +
> + return relative_level * b->props.max_brightness / scaling_factor;
> +}
Maybe
fixp_linear_interpolate(0, 0, a->props.max_brightness, b->props.max_brightness, a->props.brightness);
? (from `linux/fixp-arith.h`)
> +
> static int nvidia_wmi_ec_backlight_update_status(struct backlight_device *bd)
> {
> struct wmi_device *wdev = bl_get_data(bd);
> + struct nvidia_wmi_ec_backlight_priv *priv = dev_get_drvdata(&wdev->dev);
> + struct backlight_device *proxy_target = priv->proxy_target;
> +
> + if (proxy_target) {
> + int level = scale_backlight_level(bd, proxy_target);
> +
> + if (backlight_device_set_brightness(proxy_target, level))
> + pr_warn("Failed to relay backlight update to \"%s\"",
> + backlight_proxy_target);
> + }
>
> return wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_LEVEL,
> WMI_BRIGHTNESS_MODE_SET,
> @@ -147,13 +234,65 @@ static const struct backlight_ops nvidia_wmi_ec_backlight_ops = {
> .get_brightness = nvidia_wmi_ec_backlight_get_brightness,
> };
>
> +static int nvidia_wmi_ec_backlight_pm_notifier(struct notifier_block *nb, unsigned long event, void *d)
> +{
> +
> + /*
> + * On some systems, the EC backlight level gets reset to 100% when
> + * resuming from suspend, but the backlight device state still reflects
> + * the pre-suspend value. Refresh the existing state to sync the EC's
> + * state back up with the kernel's.
> + */
> + if (event == PM_POST_SUSPEND) {
> + struct nvidia_wmi_ec_backlight_priv *p;
> +
> + p = container_of(nb, struct nvidia_wmi_ec_backlight_priv, nb);
> + return backlight_update_status(p->bl_dev);
`backlight_update_status()` returns a negative errno while the notifier chain
expects something else. It would probably be better to return `NOTIFY_DONE`
in all cases. Currently a suitable error from `backlight_update_status()` will
stop the notifier chain.
> + }
> +
> + return 0;
> +}
> +
> static int nvidia_wmi_ec_backlight_probe(struct wmi_device *wdev, const void *ctx)
> {
> + struct backlight_device *bdev, *target = NULL;
> + struct nvidia_wmi_ec_backlight_priv *priv;
> struct backlight_properties props = {};
> - struct backlight_device *bdev;
> u32 source;
> int ret;
>
> + /*
> + * Check quirks tables to see if this system needs any of the firmware
> + * bug workarounds.
> + */
> +
> + /* User-set quirks from the module parameters take precedence */
> + if (!backlight_proxy_target)
> + dmi_check_system(proxy_quirk_table);
> +
> + dmi_check_system(restore_quirk_table);
> +
> + if (backlight_proxy_target && backlight_proxy_target[0]) {
> + static int num_reprobe_attempts;
> +
> + target = backlight_device_get_by_name(backlight_proxy_target);
> +
> + if (!target) {
> + /*
> + * The target backlight device might not be ready;
> + * try again and disable backlight proxying if it
> + * fails too many times.
> + */
> + if (num_reprobe_attempts < max_reprobe_attempts) {
> + num_reprobe_attempts++;
> + return -EPROBE_DEFER;
> + }
> +
> + pr_warn("Unable to acquire %s after %d attempts. Disabling backlight proxy.",
> + backlight_proxy_target, max_reprobe_attempts);
> + }
> + }
I think `target` is not put in case of error. You probably need to add something like:
if (target) {
ret = devm_add_action_or_reset(&wdev->dev, put_device_wrapper, target);
if (ret < 0)
return ret;
}
> +
> ret = wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_SOURCE,
> WMI_BRIGHTNESS_MODE_GET, &source);
> if (ret)
> @@ -188,7 +327,44 @@ static int nvidia_wmi_ec_backlight_probe(struct wmi_device *wdev, const void *ct
> &wdev->dev, wdev,
> &nvidia_wmi_ec_backlight_ops,
> &props);
> - return PTR_ERR_OR_ZERO(bdev);
> +
> + if (IS_ERR(bdev))
> + return PTR_ERR(bdev);
> +
> + priv = kzalloc(sizeof(*priv), GFP_KERNEL);
`devm_kzalloc()` would probably be better and you should check if `!priv`.
> + priv->bl_dev = bdev;
> +
> + dev_set_drvdata(&wdev->dev, priv);
> +
> + if (target) {
> + int level = scale_backlight_level(target, bdev);
> +
> + if (backlight_device_set_brightness(bdev, level))
> + pr_warn("Unable to import initial brightness level from %s.",
> + backlight_proxy_target);
> + priv->proxy_target = target;
> + }
> +
> + if (restore_level_on_resume) {
> + priv->nb.notifier_call = nvidia_wmi_ec_backlight_pm_notifier;
> + register_pm_notifier(&priv->nb);
> + }
> +
> + return 0;
> +}
> +
> +static void nvidia_wmi_ec_backlight_remove(struct wmi_device *wdev)
> +{
> + struct nvidia_wmi_ec_backlight_priv *priv = dev_get_drvdata(&wdev->dev);
> + struct backlight_device *proxy_target = priv->proxy_target;
> +
> + if (proxy_target)
> + put_device(&proxy_target->dev);
If you switch to `devm_add_action_or_reset()`, this will not be needed.
> +
> + if (priv->nb.notifier_call)
> + unregister_pm_notifier(&priv->nb);
> +
> + kfree(priv);
If you switch to `devm_kzalloc()`, this won't be needed.
> }
>
> #define WMI_BRIGHTNESS_GUID "603E9613-EF25-4338-A3D0-C46177516DB7"
> @@ -204,6 +380,7 @@ static struct wmi_driver nvidia_wmi_ec_backlight_driver = {
> .name = "nvidia-wmi-ec-backlight",
> },
> .probe = nvidia_wmi_ec_backlight_probe,
> + .remove = nvidia_wmi_ec_backlight_remove,
> .id_table = nvidia_wmi_ec_backlight_id_table,
> };
> module_wmi_driver(nvidia_wmi_ec_backlight_driver);
> --
> 2.27.0
>
Lastly, is it expected that these bugs will be properly fixed?
Regards,
Barnabás Pőcze
