I recently got a ThinkPad X1 Extreme 2nd Generation for fixing some
issues on, and noticed that out of the box the backlight doesn't work.
Along the way of fixing that, I found a few issues with how i915 handles
DPCD AUX backlight control and fixed them. Now I've got working
backlight controls, hooray!
Note that this patch series enables DPCD backlight controls by default.
This time however, we ignore the backlight type advertised in the VBT
(unless it's a custom backlight interface that doesn't use the standard
VESA interface over AUX) and just trust the DPCD.
Lyude Paul (5):
drm/i915: Fix eDP DPCD aux max backlight calculations
drm/i915: Assume 100% brightness when not in DPCD control mode
drm/i915: Fix DPCD register order in intel_dp_aux_enable_backlight()
drm/i915: Don't use VBT for detecting DPCD backlight controls
drm/i915: Auto detect DPCD backlight support by default
.../drm/i915/display/intel_display_types.h | 3 +
.../drm/i915/display/intel_dp_aux_backlight.c | 175 ++++++++++++------
drivers/gpu/drm/i915/i915_params.c | 2 +-
drivers/gpu/drm/i915/i915_params.h | 2 +-
4 files changed, 126 insertions(+), 56 deletions(-)
--
2.24.1
Currently we always determine the initial panel brightness level by
simply reading the value from DP_EDP_BACKLIGHT_BRIGHTNESS_MSB/LSB. This
seems wrong though, because if the panel is not currently in DPCD
control mode there's not really any reason why there would be any
brightness value programmed in the first place.
This appears to be the case on the Lenovo ThinkPad X1 Extreme 2nd
Generation, where the default value in these registers is always 0 on
boot despite the fact the panel runs at max brightness by default.
Getting the initial brightness value correct here is important as well,
since the panel on this laptop doesn't behave well if it's ever put into
DPCD control mode while the brightness level is programmed to 0.
So, let's fix this by checking what the current backlight control mode
is before reading the brightness level. If it's in DPCD control mode, we
return the programmed brightness level. Otherwise we assume 100%
brightness and return the highest possible brightness level. This also
prevents us from accidentally programming a brightness level of 0.
This is one of the many fixes that gets backlight controls working on
the ThinkPad X1 Extreme 2nd Generation with optional 4K AMOLED screen.
Changes since v1:
* s/DP_EDP_DISPLAY_CONTROL_REGISTER/DP_EDP_BACKLIGHT_MODE_SET_REGISTER/
- Jani
Tested-by: AceLan Kao <[email protected]>
Tested-by: Perry Yuan <[email protected]>
Signed-off-by: Lyude Paul <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
---
.../drm/i915/display/intel_dp_aux_backlight.c | 17 +++++++++++++++++
1 file changed, 17 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 345eed641455..5d4db5f8a165 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -59,8 +59,25 @@ static u32 intel_dp_aux_get_backlight(struct intel_connector *connector)
{
struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
u8 read_val[2] = { 0x0 };
+ u8 mode_reg;
u16 level = 0;
+ if (drm_dp_dpcd_readb(&intel_dp->aux,
+ DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
+ &mode_reg) != 1) {
+ DRM_DEBUG_KMS("Failed to read the DPCD register 0x%x\n",
+ DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
+ return 0;
+ }
+
+ /*
+ * If we're not in DPCD control mode yet, the programmed brightness
+ * value is meaningless and we should assume max brightness
+ */
+ if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
+ DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD)
+ return connector->panel.backlight.max;
+
if (drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
&read_val, sizeof(read_val)) < 0) {
DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
--
2.24.1
Max backlight value for the panel was being calculated using byte
count i.e. 0xffff if 2 bytes are supported for backlight brightness
and 0xff if 1 byte is supported. However, EDP_PWMGEN_BIT_COUNT
determines the number of active control bits used for the brightness
setting. Thus, even if the panel uses 2 byte setting, it might not use
all the control bits. Thus, max backlight should be set based on the
value of EDP_PWMGEN_BIT_COUNT instead of assuming 65535 or 255.
Additionally, EDP_PWMGEN_BIT_COUNT was being updated based on the VBT
frequency which results in a different max backlight value. Thus,
setting of EDP_PWMGEN_BIT_COUNT is moved to setup phase instead of
enable so that max backlight can be calculated correctly. Only the
frequency divider is set during the enable phase using the value of
EDP_PWMGEN_BIT_COUNT.
This is based off the original patch series from Furquan Shaikh
<[email protected]>:
https://patchwork.freedesktop.org/patch/317255/?series=62326&rev=3
Changes since original patch:
* Remove unused intel_dp variable in intel_dp_aux_setup_backlight()
* Fix checkpatch issues
* Make sure that we rewrite the pwmgen bit count whenever we bring the
panel out of D3 mode
v2 by Jani:
* rebase
* fix readb return value check
Cc: Furquan Shaikh <[email protected]>
Tested-by: AceLan Kao <[email protected]>
Tested-by: Perry Yuan <[email protected]>
Signed-off-by: Lyude Paul <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
---
.../drm/i915/display/intel_display_types.h | 3 +
.../drm/i915/display/intel_dp_aux_backlight.c | 139 ++++++++++++------
2 files changed, 95 insertions(+), 47 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index fdd943a17de3..155ce49ae764 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -214,6 +214,9 @@ struct intel_panel {
u8 controller; /* bxt+ only */
struct pwm_device *pwm;
+ /* DPCD backlight */
+ u8 pwmgen_bit_count;
+
struct backlight_device *device;
/* Connector and platform specific backlight functions */
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 7c653f8c307f..345eed641455 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -111,61 +111,28 @@ static bool intel_dp_aux_set_pwm_freq(struct intel_connector *connector)
{
struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
- int freq, fxp, fxp_min, fxp_max, fxp_actual, f = 1;
- u8 pn, pn_min, pn_max;
+ const u8 pn = connector->panel.backlight.pwmgen_bit_count;
+ int freq, fxp, f, fxp_actual, fxp_min, fxp_max;
- /* Find desired value of (F x P)
- * Note that, if F x P is out of supported range, the maximum value or
- * minimum value will applied automatically. So no need to check that.
- */
freq = dev_priv->vbt.backlight.pwm_freq_hz;
- DRM_DEBUG_KMS("VBT defined backlight frequency %u Hz\n", freq);
if (!freq) {
DRM_DEBUG_KMS("Use panel default backlight frequency\n");
return false;
}
fxp = DIV_ROUND_CLOSEST(KHz(DP_EDP_BACKLIGHT_FREQ_BASE_KHZ), freq);
+ f = clamp(DIV_ROUND_CLOSEST(fxp, 1 << pn), 1, 255);
+ fxp_actual = f << pn;
- /* Use highest possible value of Pn for more granularity of brightness
- * adjustment while satifying the conditions below.
- * - Pn is in the range of Pn_min and Pn_max
- * - F is in the range of 1 and 255
- * - FxP is within 25% of desired value.
- * Note: 25% is arbitrary value and may need some tweak.
- */
- if (drm_dp_dpcd_readb(&intel_dp->aux,
- DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &pn_min) != 1) {
- DRM_DEBUG_KMS("Failed to read pwmgen bit count cap min\n");
- return false;
- }
- if (drm_dp_dpcd_readb(&intel_dp->aux,
- DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &pn_max) != 1) {
- DRM_DEBUG_KMS("Failed to read pwmgen bit count cap max\n");
- return false;
- }
- pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
- pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
-
+ /* Ensure frequency is within 25% of desired value */
fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4);
fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4);
- if (fxp_min < (1 << pn_min) || (255 << pn_max) < fxp_max) {
- DRM_DEBUG_KMS("VBT defined backlight frequency out of range\n");
- return false;
- }
- for (pn = pn_max; pn >= pn_min; pn--) {
- f = clamp(DIV_ROUND_CLOSEST(fxp, 1 << pn), 1, 255);
- fxp_actual = f << pn;
- if (fxp_min <= fxp_actual && fxp_actual <= fxp_max)
- break;
- }
-
- if (drm_dp_dpcd_writeb(&intel_dp->aux,
- DP_EDP_PWMGEN_BIT_COUNT, pn) < 0) {
- DRM_DEBUG_KMS("Failed to write aux pwmgen bit count\n");
+ if (fxp_min > fxp_actual || fxp_actual > fxp_max) {
+ DRM_DEBUG_KMS("Actual frequency out of range\n");
return false;
}
+
if (drm_dp_dpcd_writeb(&intel_dp->aux,
DP_EDP_BACKLIGHT_FREQ_SET, (u8) f) < 0) {
DRM_DEBUG_KMS("Failed to write aux backlight freq\n");
@@ -179,6 +146,7 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st
{
struct intel_connector *connector = to_intel_connector(conn_state->connector);
struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
+ struct intel_panel *panel = &connector->panel;
u8 dpcd_buf, new_dpcd_buf, edp_backlight_mode;
if (drm_dp_dpcd_readb(&intel_dp->aux,
@@ -197,6 +165,12 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st
case DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT:
new_dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
new_dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
+
+ if (drm_dp_dpcd_writeb(&intel_dp->aux,
+ DP_EDP_PWMGEN_BIT_COUNT,
+ panel->backlight.pwmgen_bit_count) < 0)
+ DRM_DEBUG_KMS("Failed to write aux pwmgen bit count\n");
+
break;
/* Do nothing when it is already DPCD mode */
@@ -226,20 +200,91 @@ static void intel_dp_aux_disable_backlight(const struct drm_connector_state *old
false);
}
+static u32 intel_dp_aux_calc_max_backlight(struct intel_connector *connector)
+{
+ struct drm_i915_private *i915 = to_i915(connector->base.dev);
+ struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
+ struct intel_panel *panel = &connector->panel;
+ u32 max_backlight = 0;
+ int freq, fxp, fxp_min, fxp_max, fxp_actual, f = 1;
+ u8 pn, pn_min, pn_max;
+
+ if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_PWMGEN_BIT_COUNT, &pn) == 1) {
+ pn &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
+ max_backlight = (1 << pn) - 1;
+ }
+
+ /* Find desired value of (F x P)
+ * Note that, if F x P is out of supported range, the maximum value or
+ * minimum value will applied automatically. So no need to check that.
+ */
+ freq = i915->vbt.backlight.pwm_freq_hz;
+ DRM_DEBUG_KMS("VBT defined backlight frequency %u Hz\n", freq);
+ if (!freq) {
+ DRM_DEBUG_KMS("Use panel default backlight frequency\n");
+ return max_backlight;
+ }
+
+ fxp = DIV_ROUND_CLOSEST(KHz(DP_EDP_BACKLIGHT_FREQ_BASE_KHZ), freq);
+
+ /* Use highest possible value of Pn for more granularity of brightness
+ * adjustment while satifying the conditions below.
+ * - Pn is in the range of Pn_min and Pn_max
+ * - F is in the range of 1 and 255
+ * - FxP is within 25% of desired value.
+ * Note: 25% is arbitrary value and may need some tweak.
+ */
+ if (drm_dp_dpcd_readb(&intel_dp->aux,
+ DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &pn_min) != 1) {
+ DRM_DEBUG_KMS("Failed to read pwmgen bit count cap min\n");
+ return max_backlight;
+ }
+ if (drm_dp_dpcd_readb(&intel_dp->aux,
+ DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &pn_max) != 1) {
+ DRM_DEBUG_KMS("Failed to read pwmgen bit count cap max\n");
+ return max_backlight;
+ }
+ pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
+ pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
+
+ fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4);
+ fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4);
+ if (fxp_min < (1 << pn_min) || (255 << pn_max) < fxp_max) {
+ DRM_DEBUG_KMS("VBT defined backlight frequency out of range\n");
+ return max_backlight;
+ }
+
+ for (pn = pn_max; pn >= pn_min; pn--) {
+ f = clamp(DIV_ROUND_CLOSEST(fxp, 1 << pn), 1, 255);
+ fxp_actual = f << pn;
+ if (fxp_min <= fxp_actual && fxp_actual <= fxp_max)
+ break;
+ }
+
+ DRM_DEBUG_KMS("Using eDP pwmgen bit count of %d\n", pn);
+ if (drm_dp_dpcd_writeb(&intel_dp->aux,
+ DP_EDP_PWMGEN_BIT_COUNT, pn) < 0) {
+ DRM_DEBUG_KMS("Failed to write aux pwmgen bit count\n");
+ return max_backlight;
+ }
+ panel->backlight.pwmgen_bit_count = pn;
+
+ max_backlight = (1 << pn) - 1;
+
+ return max_backlight;
+}
+
static int intel_dp_aux_setup_backlight(struct intel_connector *connector,
enum pipe pipe)
{
- struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
struct intel_panel *panel = &connector->panel;
- if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
- panel->backlight.max = 0xFFFF;
- else
- panel->backlight.max = 0xFF;
+ panel->backlight.max = intel_dp_aux_calc_max_backlight(connector);
+ if (!panel->backlight.max)
+ return -ENODEV;
panel->backlight.min = 0;
panel->backlight.level = intel_dp_aux_get_backlight(connector);
-
panel->backlight.enabled = panel->backlight.level != 0;
return 0;
--
2.24.1
Turns out we actually already have some companies, such as Lenovo,
shipping machines with AMOLED screens that don't allow controlling the
backlight through the usual PWM interface and only allow controlling it
through the standard EDP DPCD interface. One example of one of these
laptops is the X1 Extreme 2nd Generation.
Since we've got systems that need this turned on by default now to have
backlight controls working out of the box, let's start auto-detecting it
for systems by default based on what the VBT tells us. We do this by
changing the default value for the enable_dpcd_backlight module param
from 0 to -1.
Tested-by: AceLan Kao <[email protected]>
Tested-by: Perry Yuan <[email protected]>
Signed-off-by: Lyude Paul <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
---
drivers/gpu/drm/i915/i915_params.c | 2 +-
drivers/gpu/drm/i915/i915_params.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 64009e99073d..905decc36e53 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -172,7 +172,7 @@ i915_param_named_unsafe(inject_probe_failure, uint, 0400,
i915_param_named(enable_dpcd_backlight, int, 0600,
"Enable support for DPCD backlight control"
- "(-1=use per-VBT LFP backlight type setting, 0=disabled [default], 1=enabled)");
+ "(-1=use per-VBT LFP backlight type setting [default], 0=disabled, 1=enabled)");
#if IS_ENABLED(CONFIG_DRM_I915_GVT)
i915_param_named(enable_gvt, bool, 0400,
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index be6089e4f9e6..947d0a38fa3c 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -66,7 +66,7 @@ struct drm_printer;
param(int, reset, 3, 0600) \
param(unsigned int, inject_probe_failure, 0, 0600) \
param(int, fastboot, -1, 0600) \
- param(int, enable_dpcd_backlight, 0, 0600) \
+ param(int, enable_dpcd_backlight, -1, 0600) \
param(char *, force_probe, CONFIG_DRM_I915_FORCE_PROBE, 0400) \
param(unsigned long, fake_lmem_start, 0, 0400) \
/* leave bools at the end to not create holes */ \
--
2.24.1
For eDP panels, it appears it's expected that so long as the panel is in
DPCD control mode that the brightness value is never set to 0. Instead,
if the desired effect is to set the panel's backlight to 0 we're
expected to simply turn off the backlight through the
DP_EDP_DISPLAY_CONTROL_REGISTER.
We already do the latter correctly in intel_dp_aux_disable_backlight().
But, we make the mistake of writing the DPCD registers in the wrong
order when enabling the backlight in intel_dp_aux_enable_backlight()
since we currently enable the backlight through
DP_EDP_DISPLAY_CONTROL_REGISTER before writing the brightness level. On
the X1 Extreme 2nd Generation, this appears to have the potential of
confusing the panel in such a way that further attempts to set the
brightness don't actually change the backlight as expected and leave it
off. Presumably, this happens because the incorrect register writing
order briefly leaves the panel with DPCD mode enabled and a 0 brightness
level set.
So, reverse the order we write the DPCD registers when enabling the
panel backlight so that we write the brightness value first, and enable
the backlight second. This fix appears to be the final bit needed to get
the backlight on the ThinkPad X1 Extreme 2nd Generation's AMOLED screen
working.
Tested-by: AceLan Kao <[email protected]>
Tested-by: Perry Yuan <[email protected]>
Signed-off-by: Lyude Paul <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
---
drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
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 5d4db5f8a165..77a759361c5c 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -207,8 +207,9 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st
}
}
+ intel_dp_aux_set_backlight(conn_state,
+ connector->panel.backlight.level);
set_aux_backlight_enable(intel_dp, true);
- intel_dp_aux_set_backlight(conn_state, connector->panel.backlight.level);
}
static void intel_dp_aux_disable_backlight(const struct drm_connector_state *old_conn_state)
--
2.24.1
Despite the fact that the VBT appears to have a field for specifying
that a system is equipped with a panel that supports standard VESA
backlight controls over the DP AUX channel, so far every system we've
spotted DPCD backlight control support on doesn't actually set this
field correctly and all have it set to INTEL_BACKLIGHT_DISPLAY_DDI.
While we don't know the exact reason for this VBT misuse, talking with
some vendors indicated that there's a good number of laptop panels out
there that supposedly support both PWM backlight controls and DPCD
backlight controls as a workaround until Intel supports DPCD backlight
controls across platforms universally. This being said, the X1 Extreme
2nd Gen that I have here (note that Lenovo is not the hardware vendor
that informed us of this) PWM backlight controls are advertised, but
only DPCD controls actually function. I'm going to make an educated
guess here and say that on systems like this one, it's likely that PWM
backlight controls might have been intended to work but were never
really tested by QA.
Since we really need backlights to work without any extra module
parameters, let's take the risk here and rely on the standard DPCD caps
to tell us whether AUX backlight controls are supported or not. We still
check the VBT, but only to make sure that we don't enable DPCD backlight
controls on a panel that uses something other then the standard VESA
interfaces over AUX. Since panels using such non-standard interfaces
should probably have support added to i915, we'll print a warning when
seeing this in the VBT. We can remove this warning later if we end up
adding support for any custom backlight interfaces.
Signed-off-by: Lyude Paul <[email protected]>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112376
Cc: Jani Nikula <[email protected]>
Cc: Perry Yuan <[email protected]>
Cc: AceLan Kao <[email protected]>
---
.../drm/i915/display/intel_dp_aux_backlight.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
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 77a759361c5c..3002b600635f 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -330,13 +330,17 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
struct intel_panel *panel = &intel_connector->panel;
struct drm_i915_private *dev_priv = to_i915(intel_connector->base.dev);
- if (i915_modparams.enable_dpcd_backlight == 0 ||
- (i915_modparams.enable_dpcd_backlight == -1 &&
- dev_priv->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
- return -ENODEV;
-
- if (!intel_dp_aux_display_control_capable(intel_connector))
+ if (i915_modparams.enable_dpcd_backlight == 0)
return -ENODEV;
+ if (i915_modparams.enable_dpcd_backlight == -1) {
+ if (dev_priv->vbt.backlight.type
+ == INTEL_BACKLIGHT_PANEL_DRIVER_INTERFACE) {
+ DRM_WARN("VBT says panel uses custom panel driver interface, not using DPCD backlight controls\n");
+ return -ENODEV;
+ }
+ if (!intel_dp_aux_display_control_capable(intel_connector))
+ return -ENODEV;
+ }
panel->backlight.setup = intel_dp_aux_setup_backlight;
panel->backlight.enable = intel_dp_aux_enable_backlight;
--
2.24.1
On Thu, 16 Jan 2020, Lyude Paul <[email protected]> wrote:
> Despite the fact that the VBT appears to have a field for specifying
> that a system is equipped with a panel that supports standard VESA
> backlight controls over the DP AUX channel, so far every system we've
> spotted DPCD backlight control support on doesn't actually set this
> field correctly and all have it set to INTEL_BACKLIGHT_DISPLAY_DDI.
>
> While we don't know the exact reason for this VBT misuse, talking with
> some vendors indicated that there's a good number of laptop panels out
> there that supposedly support both PWM backlight controls and DPCD
> backlight controls as a workaround until Intel supports DPCD backlight
> controls across platforms universally. This being said, the X1 Extreme
> 2nd Gen that I have here (note that Lenovo is not the hardware vendor
> that informed us of this) PWM backlight controls are advertised, but
> only DPCD controls actually function. I'm going to make an educated
> guess here and say that on systems like this one, it's likely that PWM
> backlight controls might have been intended to work but were never
> really tested by QA.
>
> Since we really need backlights to work without any extra module
> parameters, let's take the risk here and rely on the standard DPCD caps
> to tell us whether AUX backlight controls are supported or not. We still
> check the VBT, but only to make sure that we don't enable DPCD backlight
> controls on a panel that uses something other then the standard VESA
> interfaces over AUX. Since panels using such non-standard interfaces
> should probably have support added to i915, we'll print a warning when
> seeing this in the VBT. We can remove this warning later if we end up
> adding support for any custom backlight interfaces.
>
> Signed-off-by: Lyude Paul <[email protected]>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112376
> Cc: Jani Nikula <[email protected]>
> Cc: Perry Yuan <[email protected]>
> Cc: AceLan Kao <[email protected]>
> ---
> .../drm/i915/display/intel_dp_aux_backlight.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> 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 77a759361c5c..3002b600635f 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -330,13 +330,17 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
> struct intel_panel *panel = &intel_connector->panel;
> struct drm_i915_private *dev_priv = to_i915(intel_connector->base.dev);
>
> - if (i915_modparams.enable_dpcd_backlight == 0 ||
> - (i915_modparams.enable_dpcd_backlight == -1 &&
> - dev_priv->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
> - return -ENODEV;
> -
> - if (!intel_dp_aux_display_control_capable(intel_connector))
> + if (i915_modparams.enable_dpcd_backlight == 0)
> return -ENODEV;
> + if (i915_modparams.enable_dpcd_backlight == -1) {
> + if (dev_priv->vbt.backlight.type
> + == INTEL_BACKLIGHT_PANEL_DRIVER_INTERFACE) {
> + DRM_WARN("VBT says panel uses custom panel driver interface, not using DPCD backlight controls\n");
> + return -ENODEV;
> + }
> + if (!intel_dp_aux_display_control_capable(intel_connector))
> + return -ENODEV;
Functionally, I'm fine with trying this. But perhaps we should check aux
and early return first, and then check what vbt says, to reduce the
dmesg noise.
I'll probably want to see a debug message if we're enabling aux
backlight even if dev_priv->vbt.backlight.type !=
INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE. It's the kind of debug trace
you'll really want to get first.
BR,
Jani.
> + }
>
> panel->backlight.setup = intel_dp_aux_setup_backlight;
> panel->backlight.enable = intel_dp_aux_enable_backlight;
--
Jani Nikula, Intel Open Source Graphics Center
On Fri, 17 Jan 2020, Jani Nikula <[email protected]> wrote:
> On Thu, 16 Jan 2020, Lyude Paul <[email protected]> wrote:
>> Despite the fact that the VBT appears to have a field for specifying
>> that a system is equipped with a panel that supports standard VESA
>> backlight controls over the DP AUX channel, so far every system we've
>> spotted DPCD backlight control support on doesn't actually set this
>> field correctly and all have it set to INTEL_BACKLIGHT_DISPLAY_DDI.
>>
>> While we don't know the exact reason for this VBT misuse, talking with
>> some vendors indicated that there's a good number of laptop panels out
>> there that supposedly support both PWM backlight controls and DPCD
>> backlight controls as a workaround until Intel supports DPCD backlight
>> controls across platforms universally. This being said, the X1 Extreme
>> 2nd Gen that I have here (note that Lenovo is not the hardware vendor
>> that informed us of this) PWM backlight controls are advertised, but
>> only DPCD controls actually function. I'm going to make an educated
>> guess here and say that on systems like this one, it's likely that PWM
>> backlight controls might have been intended to work but were never
>> really tested by QA.
>>
>> Since we really need backlights to work without any extra module
>> parameters, let's take the risk here and rely on the standard DPCD caps
>> to tell us whether AUX backlight controls are supported or not. We still
>> check the VBT, but only to make sure that we don't enable DPCD backlight
>> controls on a panel that uses something other then the standard VESA
>> interfaces over AUX. Since panels using such non-standard interfaces
>> should probably have support added to i915, we'll print a warning when
>> seeing this in the VBT. We can remove this warning later if we end up
>> adding support for any custom backlight interfaces.
>>
>> Signed-off-by: Lyude Paul <[email protected]>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112376
>> Cc: Jani Nikula <[email protected]>
>> Cc: Perry Yuan <[email protected]>
>> Cc: AceLan Kao <[email protected]>
>> ---
>> .../drm/i915/display/intel_dp_aux_backlight.c | 16 ++++++++++------
>> 1 file changed, 10 insertions(+), 6 deletions(-)
>>
>> 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 77a759361c5c..3002b600635f 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>> @@ -330,13 +330,17 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
>> struct intel_panel *panel = &intel_connector->panel;
>> struct drm_i915_private *dev_priv = to_i915(intel_connector->base.dev);
>>
>> - if (i915_modparams.enable_dpcd_backlight == 0 ||
>> - (i915_modparams.enable_dpcd_backlight == -1 &&
>> - dev_priv->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
>> - return -ENODEV;
>> -
>> - if (!intel_dp_aux_display_control_capable(intel_connector))
>> + if (i915_modparams.enable_dpcd_backlight == 0)
>> return -ENODEV;
>> + if (i915_modparams.enable_dpcd_backlight == -1) {
>> + if (dev_priv->vbt.backlight.type
>> + == INTEL_BACKLIGHT_PANEL_DRIVER_INTERFACE) {
>> + DRM_WARN("VBT says panel uses custom panel driver interface, not using DPCD backlight controls\n");
>> + return -ENODEV;
>> + }
>> + if (!intel_dp_aux_display_control_capable(intel_connector))
>> + return -ENODEV;
>
> Functionally, I'm fine with trying this. But perhaps we should check aux
> and early return first, and then check what vbt says, to reduce the
> dmesg noise.
>
> I'll probably want to see a debug message if we're enabling aux
> backlight even if dev_priv->vbt.backlight.type !=
> INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE. It's the kind of debug trace
> you'll really want to get first.
So I've gone ahead and pushed patches 1-3 and 5 in this series, as they
were tested as part of the series I posted.
BR,
Jani.
>
> BR,
> Jani.
>
>
>
>> + }
>>
>> panel->backlight.setup = intel_dp_aux_setup_backlight;
>> panel->backlight.enable = intel_dp_aux_enable_backlight;
--
Jani Nikula, Intel Open Source Graphics Center
On Fri, 2020-01-17 at 13:36 +0200, Jani Nikula wrote:
> On Thu, 16 Jan 2020, Lyude Paul <[email protected]> wrote:
> > Despite the fact that the VBT appears to have a field for specifying
> > that a system is equipped with a panel that supports standard VESA
> > backlight controls over the DP AUX channel, so far every system we've
> > spotted DPCD backlight control support on doesn't actually set this
> > field correctly and all have it set to INTEL_BACKLIGHT_DISPLAY_DDI.
> >
> > While we don't know the exact reason for this VBT misuse, talking with
> > some vendors indicated that there's a good number of laptop panels out
> > there that supposedly support both PWM backlight controls and DPCD
> > backlight controls as a workaround until Intel supports DPCD backlight
> > controls across platforms universally. This being said, the X1 Extreme
> > 2nd Gen that I have here (note that Lenovo is not the hardware vendor
> > that informed us of this) PWM backlight controls are advertised, but
> > only DPCD controls actually function. I'm going to make an educated
> > guess here and say that on systems like this one, it's likely that PWM
> > backlight controls might have been intended to work but were never
> > really tested by QA.
> >
> > Since we really need backlights to work without any extra module
> > parameters, let's take the risk here and rely on the standard DPCD caps
> > to tell us whether AUX backlight controls are supported or not. We still
> > check the VBT, but only to make sure that we don't enable DPCD backlight
> > controls on a panel that uses something other then the standard VESA
> > interfaces over AUX. Since panels using such non-standard interfaces
> > should probably have support added to i915, we'll print a warning when
> > seeing this in the VBT. We can remove this warning later if we end up
> > adding support for any custom backlight interfaces.
> >
> > Signed-off-by: Lyude Paul <[email protected]>
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112376
> > Cc: Jani Nikula <[email protected]>
> > Cc: Perry Yuan <[email protected]>
> > Cc: AceLan Kao <[email protected]>
> > ---
> > .../drm/i915/display/intel_dp_aux_backlight.c | 16 ++++++++++------
> > 1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > 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 77a759361c5c..3002b600635f 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > @@ -330,13 +330,17 @@ int intel_dp_aux_init_backlight_funcs(struct
> > intel_connector *intel_connector)
> > struct intel_panel *panel = &intel_connector->panel;
> > struct drm_i915_private *dev_priv = to_i915(intel_connector-
> > >base.dev);
> >
> > - if (i915_modparams.enable_dpcd_backlight == 0 ||
> > - (i915_modparams.enable_dpcd_backlight == -1 &&
> > - dev_priv->vbt.backlight.type !=
> > INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
> > - return -ENODEV;
> > -
> > - if (!intel_dp_aux_display_control_capable(intel_connector))
> > + if (i915_modparams.enable_dpcd_backlight == 0)
> > return -ENODEV;
> > + if (i915_modparams.enable_dpcd_backlight == -1) {
> > + if (dev_priv->vbt.backlight.type
> > + == INTEL_BACKLIGHT_PANEL_DRIVER_INTERFACE) {
> > + DRM_WARN("VBT says panel uses custom panel driver
> > interface, not using DPCD backlight controls\n");
> > + return -ENODEV;
> > + }
> > + if (!intel_dp_aux_display_control_capable(intel_connector))
> > + return -ENODEV;
>
> Functionally, I'm fine with trying this. But perhaps we should check aux
> and early return first, and then check what vbt says, to reduce the
> dmesg noise.
>
> I'll probably want to see a debug message if we're enabling aux
> backlight even if dev_priv->vbt.backlight.type !=
> INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE. It's the kind of debug trace
> you'll really want to get first.
Good point, I'll send a respin of this patch with those changes
>
> BR,
> Jani.
>
>
>
> > + }
> >
> > panel->backlight.setup = intel_dp_aux_setup_backlight;
> > panel->backlight.enable = intel_dp_aux_enable_backlight;
--
Cheers,
Lyude Paul
Despite the fact that the VBT appears to have a field for specifying
that a system is equipped with a panel that supports standard VESA
backlight controls over the DP AUX channel, so far every system we've
spotted DPCD backlight control support on doesn't actually set this
field correctly and all have it set to INTEL_BACKLIGHT_DISPLAY_DDI.
While we don't know the exact reason for this VBT misuse, talking with
some vendors indicated that there's a good number of laptop panels out
there that supposedly support both PWM backlight controls and DPCD
backlight controls as a workaround until Intel supports DPCD backlight
controls across platforms universally. This being said, the X1 Extreme
2nd Gen that I have here (note that Lenovo is not the hardware vendor
that informed us of this) PWM backlight controls are advertised, but
only DPCD controls actually function. I'm going to make an educated
guess here and say that on systems like this one, it's likely that PWM
backlight controls might have been intended to work but were never
really tested by QA.
Since we really need backlights to work without any extra module
parameters, let's take the risk here and rely on the standard DPCD caps
to tell us whether AUX backlight controls are supported or not. We still
check the VBT, just so we can print a debugging message on systems that
advertise DPCD backlight support on the panel but not in the VBT.
Changes since v3:
* Print a debugging message if we enable DPCD backlight control on a
device which doesn't report DPCD backlight controls in it's VBT,
instead of warning on custom panel backlight interfaces.
Signed-off-by: Lyude Paul <[email protected]>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112376
Cc: Jani Nikula <[email protected]>
Cc: Perry Yuan <[email protected]>
Cc: AceLan Kao <[email protected]>
---
drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
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 77a759361c5c..0f8edc775375 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -328,15 +328,16 @@ intel_dp_aux_display_control_capable(struct intel_connector *connector)
int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
{
struct intel_panel *panel = &intel_connector->panel;
- struct drm_i915_private *dev_priv = to_i915(intel_connector->base.dev);
+ enum intel_backlight_type type =
+ to_i915(intel_connector->base.dev)->vbt.backlight.type;
if (i915_modparams.enable_dpcd_backlight == 0 ||
(i915_modparams.enable_dpcd_backlight == -1 &&
- dev_priv->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
+ !intel_dp_aux_display_control_capable(intel_connector)))
return -ENODEV;
- if (!intel_dp_aux_display_control_capable(intel_connector))
- return -ENODEV;
+ if (type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE)
+ DRM_DEBUG_DRIVER("Ignoring VBT backlight type\n");
panel->backlight.setup = intel_dp_aux_setup_backlight;
panel->backlight.enable = intel_dp_aux_enable_backlight;
--
2.24.1
On Fri, 17 Jan 2020, Lyude Paul <[email protected]> wrote:
> Despite the fact that the VBT appears to have a field for specifying
> that a system is equipped with a panel that supports standard VESA
> backlight controls over the DP AUX channel, so far every system we've
> spotted DPCD backlight control support on doesn't actually set this
> field correctly and all have it set to INTEL_BACKLIGHT_DISPLAY_DDI.
>
> While we don't know the exact reason for this VBT misuse, talking with
> some vendors indicated that there's a good number of laptop panels out
> there that supposedly support both PWM backlight controls and DPCD
> backlight controls as a workaround until Intel supports DPCD backlight
> controls across platforms universally. This being said, the X1 Extreme
> 2nd Gen that I have here (note that Lenovo is not the hardware vendor
> that informed us of this) PWM backlight controls are advertised, but
> only DPCD controls actually function. I'm going to make an educated
> guess here and say that on systems like this one, it's likely that PWM
> backlight controls might have been intended to work but were never
> really tested by QA.
>
> Since we really need backlights to work without any extra module
> parameters, let's take the risk here and rely on the standard DPCD caps
> to tell us whether AUX backlight controls are supported or not. We still
> check the VBT, just so we can print a debugging message on systems that
> advertise DPCD backlight support on the panel but not in the VBT.
>
> Changes since v3:
> * Print a debugging message if we enable DPCD backlight control on a
> device which doesn't report DPCD backlight controls in it's VBT,
> instead of warning on custom panel backlight interfaces.
>
> Signed-off-by: Lyude Paul <[email protected]>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112376
> Cc: Jani Nikula <[email protected]>
> Cc: Perry Yuan <[email protected]>
> Cc: AceLan Kao <[email protected]>
Thanks for the patch, pushed to dinq, fingers crossed! ;)
BR,
Jani.
> ---
> drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> 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 77a759361c5c..0f8edc775375 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -328,15 +328,16 @@ intel_dp_aux_display_control_capable(struct intel_connector *connector)
> int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
> {
> struct intel_panel *panel = &intel_connector->panel;
> - struct drm_i915_private *dev_priv = to_i915(intel_connector->base.dev);
> + enum intel_backlight_type type =
> + to_i915(intel_connector->base.dev)->vbt.backlight.type;
>
> if (i915_modparams.enable_dpcd_backlight == 0 ||
> (i915_modparams.enable_dpcd_backlight == -1 &&
> - dev_priv->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
> + !intel_dp_aux_display_control_capable(intel_connector)))
> return -ENODEV;
>
> - if (!intel_dp_aux_display_control_capable(intel_connector))
> - return -ENODEV;
> + if (type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE)
> + DRM_DEBUG_DRIVER("Ignoring VBT backlight type\n");
>
> panel->backlight.setup = intel_dp_aux_setup_backlight;
> panel->backlight.enable = intel_dp_aux_enable_backlight;
--
Jani Nikula, Intel Open Source Graphics Center