Panel in my Dell XPS 7590, that uses Intel's HDR backlight interface to control brightness, apparently needs a delay before setting brightness after power on. Without this delay the panel does accept the setting and may come up with some arbitrary brightness (sometimes it's too dark, sometimes it's too bright, I wasn't able to find a system).
I don't have access to the spec, so I'm not sure if it's expected behavior or a quirk for particular device.
Delay was chosen by experiment: it works with 100ms, but fails with anything lower than 75ms.
Signed-off-by: Vasily Khoruzhick anarsoul@gmail.com --- drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c index 4f8337c7fd2e..c4f35e1b5870 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -210,6 +210,10 @@ intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state,
ctrl = old_ctrl; if (panel->backlight.edp.intel.sdr_uses_aux) { + /* Wait 100ms to ensure that panel is ready otherwise it may not + * set chosen backlight level + */ + msleep(100); ctrl |= INTEL_EDP_HDR_TCON_BRIGHTNESS_AUX_ENABLE; intel_dp_aux_hdr_set_aux_backlight(conn_state, level); } else {
On Mon, 13 Sep 2021, Vasily Khoruzhick anarsoul@gmail.com wrote:
Panel in my Dell XPS 7590, that uses Intel's HDR backlight interface to control brightness, apparently needs a delay before setting brightness after power on. Without this delay the panel does accept the setting and may come up with some arbitrary brightness (sometimes it's too dark, sometimes it's too bright, I wasn't able to find a system).
I don't have access to the spec, so I'm not sure if it's expected behavior or a quirk for particular device.
Delay was chosen by experiment: it works with 100ms, but fails with anything lower than 75ms.
Looks like we don't respect the panel delays for DPCD backlight. The values are used for setting up the panel power sequencer, and thus PWM based backlight, but we should probably use the delays in DPCD backlight code too.
BR, Jani.
Signed-off-by: Vasily Khoruzhick anarsoul@gmail.com
drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c index 4f8337c7fd2e..c4f35e1b5870 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -210,6 +210,10 @@ intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state,
ctrl = old_ctrl; if (panel->backlight.edp.intel.sdr_uses_aux) {
/* Wait 100ms to ensure that panel is ready otherwise it may not* set chosen backlight level*/msleep(100);
On Tue, 2021-09-14 at 12:09 +0300, Jani Nikula wrote:
On Mon, 13 Sep 2021, Vasily Khoruzhick anarsoul@gmail.com wrote:
Panel in my Dell XPS 7590, that uses Intel's HDR backlight interface to control brightness, apparently needs a delay before setting brightness after power on. Without this delay the panel does accept the setting and may come up with some arbitrary brightness (sometimes it's too dark, sometimes it's too bright, I wasn't able to find a system).
I don't have access to the spec, so I'm not sure if it's expected behavior or a quirk for particular device.
Delay was chosen by experiment: it works with 100ms, but fails with anything lower than 75ms.
Looks like we don't respect the panel delays for DPCD backlight. The values are used for setting up the panel power sequencer, and thus PWM based backlight, but we should probably use the delays in DPCD backlight code too.
This makes sense to me, you're referring to the panel delays in the VBT correct?
BR, Jani.
Signed-off-by: Vasily Khoruzhick anarsoul@gmail.com
drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c index 4f8337c7fd2e..c4f35e1b5870 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -210,6 +210,10 @@ intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state, ctrl = old_ctrl; if (panel->backlight.edp.intel.sdr_uses_aux) { + /* Wait 100ms to ensure that panel is ready otherwise it may not + * set chosen backlight level + */ + msleep(100); ctrl |= INTEL_EDP_HDR_TCON_BRIGHTNESS_AUX_ENABLE; intel_dp_aux_hdr_set_aux_backlight(conn_state, level); } else {
On Tue, 14 Sep 2021, Lyude Paul lyude@redhat.com wrote:
On Tue, 2021-09-14 at 12:09 +0300, Jani Nikula wrote:
On Mon, 13 Sep 2021, Vasily Khoruzhick anarsoul@gmail.com wrote:
Panel in my Dell XPS 7590, that uses Intel's HDR backlight interface to control brightness, apparently needs a delay before setting brightness after power on. Without this delay the panel does accept the setting and may come up with some arbitrary brightness (sometimes it's too dark, sometimes it's too bright, I wasn't able to find a system).
I don't have access to the spec, so I'm not sure if it's expected behavior or a quirk for particular device.
Delay was chosen by experiment: it works with 100ms, but fails with anything lower than 75ms.
Looks like we don't respect the panel delays for DPCD backlight. The values are used for setting up the panel power sequencer, and thus PWM based backlight, but we should probably use the delays in DPCD backlight code too.
This makes sense to me, you're referring to the panel delays in the VBT correct?
Yes. See pps_init_delays() and intel_pps_backlight_on(). The delays aren't applied to DPCD backlight, I think it would make sense if they were.
BR, Jani.
BR, Jani.
Signed-off-by: Vasily Khoruzhick anarsoul@gmail.com
drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c index 4f8337c7fd2e..c4f35e1b5870 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -210,6 +210,10 @@ intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state, ctrl = old_ctrl; if (panel->backlight.edp.intel.sdr_uses_aux) { + /* Wait 100ms to ensure that panel is ready otherwise it may not + * set chosen backlight level + */ + msleep(100); ctrl |= INTEL_EDP_HDR_TCON_BRIGHTNESS_AUX_ENABLE; intel_dp_aux_hdr_set_aux_backlight(conn_state, level); } else {
On Tue, Sep 14, 2021 at 3:31 PM Jani Nikula jani.nikula@linux.intel.com wrote:
On Tue, 14 Sep 2021, Lyude Paul lyude@redhat.com wrote:
On Tue, 2021-09-14 at 12:09 +0300, Jani Nikula wrote:
On Mon, 13 Sep 2021, Vasily Khoruzhick anarsoul@gmail.com wrote:
Panel in my Dell XPS 7590, that uses Intel's HDR backlight interface to control brightness, apparently needs a delay before setting brightness after power on. Without this delay the panel does accept the setting and may come up with some arbitrary brightness (sometimes it's too dark, sometimes it's too bright, I wasn't able to find a system).
I don't have access to the spec, so I'm not sure if it's expected behavior or a quirk for particular device.
Delay was chosen by experiment: it works with 100ms, but fails with anything lower than 75ms.
Looks like we don't respect the panel delays for DPCD backlight. The values are used for setting up the panel power sequencer, and thus PWM based backlight, but we should probably use the delays in DPCD backlight code too.
This makes sense to me, you're referring to the panel delays in the VBT correct?
Yes. See pps_init_delays() and intel_pps_backlight_on(). The delays aren't applied to DPCD backlight, I think it would make sense if they were.
I guess it explains why it usually stops working after suspend. Probably BIOS doesn't re-init the power sequencer on resume.
BR, Jani.
BR, Jani.
Signed-off-by: Vasily Khoruzhick anarsoul@gmail.com
drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c index 4f8337c7fd2e..c4f35e1b5870 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -210,6 +210,10 @@ intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state,
ctrl = old_ctrl; if (panel->backlight.edp.intel.sdr_uses_aux) {
/* Wait 100ms to ensure that panel is ready otherwise itmay not
* set chosen backlight level*/msleep(100); ctrl |= INTEL_EDP_HDR_TCON_BRIGHTNESS_AUX_ENABLE; intel_dp_aux_hdr_set_aux_backlight(conn_state, level); } else {-- Jani Nikula, Intel Open Source Graphics Center
On Tue, 14 Sep 2021, Vasily Khoruzhick anarsoul@gmail.com wrote:
On Tue, Sep 14, 2021 at 3:31 PM Jani Nikula jani.nikula@linux.intel.com wrote:
On Tue, 14 Sep 2021, Lyude Paul lyude@redhat.com wrote:
On Tue, 2021-09-14 at 12:09 +0300, Jani Nikula wrote:
On Mon, 13 Sep 2021, Vasily Khoruzhick anarsoul@gmail.com wrote:
Panel in my Dell XPS 7590, that uses Intel's HDR backlight interface to control brightness, apparently needs a delay before setting brightness after power on. Without this delay the panel does accept the setting and may come up with some arbitrary brightness (sometimes it's too dark, sometimes it's too bright, I wasn't able to find a system).
I don't have access to the spec, so I'm not sure if it's expected behavior or a quirk for particular device.
Delay was chosen by experiment: it works with 100ms, but fails with anything lower than 75ms.
Looks like we don't respect the panel delays for DPCD backlight. The values are used for setting up the panel power sequencer, and thus PWM based backlight, but we should probably use the delays in DPCD backlight code too.
This makes sense to me, you're referring to the panel delays in the VBT correct?
Yes. See pps_init_delays() and intel_pps_backlight_on(). The delays aren't applied to DPCD backlight, I think it would make sense if they were.
I guess it explains why it usually stops working after suspend. Probably BIOS doesn't re-init the power sequencer on resume.
The point is, the DPCD backlight isn't driven via the power sequencer, while the PWM pin would be.
Please file a bug at [1], and attach /sys/kernel/debug/dri/0/i915_vbt as well as dmesg from boot with drm.debug=14 module parameter set.
Thanks, Jani.
[1] https://gitlab.freedesktop.org/drm/intel/issues/new
BR, Jani.
BR, Jani.
Signed-off-by: Vasily Khoruzhick anarsoul@gmail.com
drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c index 4f8337c7fd2e..c4f35e1b5870 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -210,6 +210,10 @@ intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state,
ctrl = old_ctrl; if (panel->backlight.edp.intel.sdr_uses_aux) {
/* Wait 100ms to ensure that panel is ready otherwise itmay not
* set chosen backlight level*/msleep(100); ctrl |= INTEL_EDP_HDR_TCON_BRIGHTNESS_AUX_ENABLE; intel_dp_aux_hdr_set_aux_backlight(conn_state, level); } else {-- Jani Nikula, Intel Open Source Graphics Center
On Wed, Sep 15, 2021 at 1:47 AM Jani Nikula jani.nikula@linux.intel.com wrote:
On Tue, 14 Sep 2021, Vasily Khoruzhick anarsoul@gmail.com wrote:
On Tue, Sep 14, 2021 at 3:31 PM Jani Nikula jani.nikula@linux.intel.com wrote:
On Tue, 14 Sep 2021, Lyude Paul lyude@redhat.com wrote:
On Tue, 2021-09-14 at 12:09 +0300, Jani Nikula wrote:
On Mon, 13 Sep 2021, Vasily Khoruzhick anarsoul@gmail.com wrote:
Panel in my Dell XPS 7590, that uses Intel's HDR backlight interface to control brightness, apparently needs a delay before setting brightness after power on. Without this delay the panel does accept the setting and may come up with some arbitrary brightness (sometimes it's too dark, sometimes it's too bright, I wasn't able to find a system).
I don't have access to the spec, so I'm not sure if it's expected behavior or a quirk for particular device.
Delay was chosen by experiment: it works with 100ms, but fails with anything lower than 75ms.
Looks like we don't respect the panel delays for DPCD backlight. The values are used for setting up the panel power sequencer, and thus PWM based backlight, but we should probably use the delays in DPCD backlight code too.
This makes sense to me, you're referring to the panel delays in the VBT correct?
Yes. See pps_init_delays() and intel_pps_backlight_on(). The delays aren't applied to DPCD backlight, I think it would make sense if they were.
I guess it explains why it usually stops working after suspend. Probably BIOS doesn't re-init the power sequencer on resume.
The point is, the DPCD backlight isn't driven via the power sequencer, while the PWM pin would be.
Please file a bug at [1], and attach /sys/kernel/debug/dri/0/i915_vbt as well as dmesg from boot with drm.debug=14 module parameter set.
Done, see https://gitlab.freedesktop.org/drm/intel/-/issues/4170
Thanks, Jani.
[1] https://gitlab.freedesktop.org/drm/intel/issues/new
BR, Jani.
BR, Jani.
Signed-off-by: Vasily Khoruzhick anarsoul@gmail.com
drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c index 4f8337c7fd2e..c4f35e1b5870 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -210,6 +210,10 @@ intel_dp_aux_hdr_enable_backlight(const struct intel_crtc_state *crtc_state,
ctrl = old_ctrl; if (panel->backlight.edp.intel.sdr_uses_aux) {
/* Wait 100ms to ensure that panel is ready otherwise itmay not
* set chosen backlight level*/msleep(100); ctrl |= INTEL_EDP_HDR_TCON_BRIGHTNESS_AUX_ENABLE; intel_dp_aux_hdr_set_aux_backlight(conn_state, level); } else {-- Jani Nikula, Intel Open Source Graphics Center
-- Jani Nikula, Intel Open Source Graphics Center
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