> Note: the Tested-by: line above applies to the previous version of this
> patch; an explicit ACK from the tester is required for it to apply to
> the current version.
I compiled and tested v2 on 5.16.14.
Everything works as expected: brightness control & level restore work
both on first boot and on subsequent sleep/resume cycles.
Regards,
Alex
On Wed, 16 Mar 2022 at 23:28, Daniel Dadap <ddadap@xxxxxxxxxx> wrote:
>
> Sorry, just noticed a typo in a comment:
>
> /* This quirk is preset as of firmware revision HACN31WW */
>
> Obviously that is meant to read "present". I'll fix that with the next
> round of changes, assuming there will be additional review feedback.
>
> On 3/16/22 15:33, Daniel Dadap wrote:
> > 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 issues, add a quirk table 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
> > separately 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>
> > ---
> > Note: the Tested-by: line above applies to the previous version of this
> > patch; an explicit ACK from the tester is required for it to apply to
> > the current version.
> >
> > v2:
> > * Add readable sysfs files for module params, use linear interpolation
> > from fixp-arith.h, fix return value of notifier callback, use devm_*()
> > for kzalloc and put_device. (Barnabás Pőcze <pobrn@xxxxxxxxxxxxxx>)
> > * Add comment to denote known firmware versions that exhibit the bugs.
> > (Mario Limonciello <Mario.Limonciello@xxxxxxx>)
> > * Unify separate per-quirk tables. (Hans de Goede <hdegoede@xxxxxxxxxx>)
> >
> > .../platform/x86/nvidia-wmi-ec-backlight.c | 196 +++++++++++++++++-
> > 1 file changed, 194 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..95e1ddf780fc 100644
> > --- a/drivers/platform/x86/nvidia-wmi-ec-backlight.c
> > +++ b/drivers/platform/x86/nvidia-wmi-ec-backlight.c
> > @@ -3,8 +3,12 @@
> > * Copyright (c) 2020, NVIDIA CORPORATION. All rights reserved.
> > */
> >
> > +#define pr_fmt(f) KBUILD_MODNAME ": " f "\n"
> > +
> > #include <linux/acpi.h>
> > #include <linux/backlight.h>
> > +#include <linux/dmi.h>
> > +#include <linux/fixp-arith.h>
> > #include <linux/mod_devicetable.h>
> > #include <linux/module.h>
> > #include <linux/types.h>
> > @@ -75,6 +79,73 @@ 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, 0444);
> > +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;
> > +module_param(max_reprobe_attempts, int, 0444);
> > +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, 0444);
> > +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.");
> > +
> > +/* Bit field values for quirks table */
> > +
> > +#define NVIDIA_WMI_EC_BACKLIGHT_QUIRK_RESTORE_LEVEL_ON_RESUME BIT(0)
> > +
> > +/* bits 1-7: reserved for future quirks; bits 8+: proxy target device names */
> > +
> > +#define NVIDIA_WMI_EC_BACKLIGHT_QUIRK_PROXY_TO_AMDGPU_BL1 BIT(8)
> > +
> > +#define QUIRK(name) NVIDIA_WMI_EC_BACKLIGHT_QUIRK_##name
> > +#define HAS_QUIRK(data, name) (((long) data) & QUIRK(name))
> > +
> > +static int assign_quirks(const struct dmi_system_id *id)
> > +{
> > + if (HAS_QUIRK(id->driver_data, RESTORE_LEVEL_ON_RESUME))
> > + restore_level_on_resume = 1;
> > +
> > + /* If the module parameter is set, override the quirks table */
> > + if (!backlight_proxy_target) {
> > + if (HAS_QUIRK(id->driver_data, PROXY_TO_AMDGPU_BL1))
> > + backlight_proxy_target = "amdgpu_bl1";
> > + }
> > +
> > + return true;
> > +}
> > +
> > +#define QUIRK_ENTRY(vendor, product, quirks) { \
> > + .callback = assign_quirks, \
> > + .matches = { \
> > + DMI_MATCH(DMI_SYS_VENDOR, vendor), \
> > + DMI_MATCH(DMI_PRODUCT_VERSION, product) \
> > + }, \
> > + .driver_data = (void *)(quirks) \
> > +}
> > +
> > +static const struct dmi_system_id quirks_table[] = {
> > + QUIRK_ENTRY(
> > + /* This quirk is preset as of firmware revision HACN31WW */
> > + "LENOVO", "Legion S7 15ACH6",
> > + QUIRK(RESTORE_LEVEL_ON_RESUME) | QUIRK(PROXY_TO_AMDGPU_BL1)
> > + ),
> > + { }
> > +};
> > +
> > /**
> > * 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 +190,30 @@ static int wmi_brightness_notify(struct wmi_device *w, enum wmi_brightness_metho
> > return 0;
> > }
> >
> > +/* Scale the current brightness level of 'from' to the range of 'to'. */
> > +static int scale_backlight_level(const struct backlight_device *from,
> > + const struct backlight_device *to)
> > +{
> > + int from_max = from->props.max_brightness;
> > + int from_level = from->props.brightness;
> > + int to_max = to->props.max_brightness;
> > +
> > + return fixp_linear_interpolate(0, 0, from_max, to_max, from_level);
> > +}
> > +
> > 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 +239,78 @@ 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;
> > + int ret;
> > +
> > + p = container_of(nb, struct nvidia_wmi_ec_backlight_priv, nb);
> > + ret = backlight_update_status(p->bl_dev);
> > +
> > + if (ret)
> > + pr_warn("failed to refresh backlight level: %d", ret);
> > +
> > + return NOTIFY_OK;
> > + }
> > +
> > + return NOTIFY_DONE;
> > +}
> > +
> > +static void putdev(void *data)
> > +{
> > + struct device *dev = data;
> > +
> > + put_device(dev);
> > +}
> > +
> > 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.
> > + */
> > + dmi_check_system(quirks_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) {
> > + ret = devm_add_action_or_reset(&wdev->dev, putdev,
> > + &target->dev);
> > + if (ret)
> > + return ret;
> > + } else {
> > + /*
> > + * 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);
> > + }
> > + }
> > +
> > ret = wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_SOURCE,
> > WMI_BRIGHTNESS_MODE_GET, &source);
> > if (ret)
> > @@ -188,7 +345,41 @@ 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 = devm_kzalloc(&wdev->dev, sizeof(*priv), GFP_KERNEL);
> > + if (!priv)
> > + return -ENOMEM;
> > +
> > + 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);
> > +
> > + if (priv->nb.notifier_call)
> > + unregister_pm_notifier(&priv->nb);
> > }
> >
> > #define WMI_BRIGHTNESS_GUID "603E9613-EF25-4338-A3D0-C46177516DB7"
> > @@ -204,6 +395,7 @@ 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);
