On Thu, 2020-11-26 at 12:51 +0200, Jani Nikula wrote:
On Wed, 16 Sep 2020, Lyude Paul lyude@redhat.com wrote:
Since we're about to start adding support for Intel's magic HDR backlight interface over DPCD, we need to ensure we're properly programming this field so that Intel specific sink services are exposed. Otherwise, 0x300-0x3ff will just read zeroes.
We also take care not to reprogram the source OUI if it already matches what we expect. This is just to be careful so that we don't accidentally take the panel out of any backlight control modes we found it in.
v2:
- Add careful parameter to intel_edp_init_source_oui() to avoid
re-writing the source OUI if it's already been set during driver initialization
Signed-off-by: Lyude Paul lyude@redhat.com Cc: thaytan@noraisin.net Cc: Vasily Khoruzhick anarsoul@gmail.com
drivers/gpu/drm/i915/display/intel_dp.c | 33 +++++++++++++++++++++++++ 1 file changed, 33 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 4bd10456ad188..7db2b6a3cd52e 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -3424,6 +3424,29 @@ void intel_dp_sink_set_decompression_state(struct intel_dp *intel_dp, enable ? "enable" : "disable"); } +static void +intel_edp_init_source_oui(struct intel_dp *intel_dp, bool careful) +{ + struct drm_i915_private *i915 = dp_to_i915(intel_dp); + u8 oui[] = { 0x00, 0xaa, 0x01 };
Nitpick, could be static const.
+ u8 buf[3] = { 0 };
+ /* + * During driver init, we want to be careful and avoid changing the source OUI if it's + * already set to what we want, so as to avoid clearing any state by accident + */
Did you actually observe any ill behaviour with unconditionally writing the source OUI?
I mean it's easy to add the "careful" mode afterwards if there are concrete issues, but it'll be hard to remove because it'll be a functional change potentially causing regressions.
I haven't yet, although I'll give a test on some of the other machines I've got lying around.
FWIW, relevant spec info:
A Sink device that does not support the Source-device specified behavior specified by the owner of the IEEE OUI written to in DPCD Addresses 00300h through 00302h as being associated with the Source Identification shall AUX_ACK all writes, but take no other action, and shall respond to reads with an AUX_ACK and the value 00h.
+ if (careful) { + if (drm_dp_dpcd_read(&intel_dp->aux, DP_SOURCE_OUI, buf, sizeof(buf)) < 0) + drm_err(&i915->drm, "Failed to read source OUI\n");
+ if (memcmp(oui, buf, sizeof(oui)) == 0) + return; + }
+ if (drm_dp_dpcd_write(&intel_dp->aux, DP_SOURCE_OUI, oui, sizeof(oui)) < 0) + drm_err(&i915->drm, "Failed to write source OUI\n"); +}
/* If the sink supports it, try to set the power state appropriately */ void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode) { @@ -3443,6 +3466,10 @@ void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode) } else { struct intel_lspcon *lspcon = dp_to_lspcon(intel_dp); + /* Write the source OUI as early as possible */ + if (intel_dp_is_edp(intel_dp)) + intel_edp_init_source_oui(intel_dp, false);
This hunk conflicts, will need a rebase.
BR, Jani.
/* * When turning on, we need to retry for 1ms to give the sink * time to wake up. @@ -4607,6 +4634,12 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp) if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv)) intel_dp_get_dsc_sink_cap(intel_dp); + /* + * If needed, program our source OUI so we can make various Intel- specific AUX services + * available (such as HDR backlight controls) + */ + intel_edp_init_source_oui(intel_dp, true);
return true; }