On Mon, 14 Aug 2017, Manasi Navare <manasi.d.navare@xxxxxxxxx> wrote: > On Fri, Aug 11, 2017 at 02:39:07PM +0300, Jani Nikula wrote: >> Ever since we've parsed VBT child devices, starting from 6acab15a7b0d >> ("drm/i915: use the HDMI DDI buffer translations from VBT"), we've >> ignored the child device information if more than one child device >> references the same port. The rationale for this seems lost in time. >> >> Since commit 311a20949f04 ("drm/i915: don't init DP or HDMI when not >> supported by DDI port") we started using this information more to skip >> HDMI/DP init if the port wasn't there per VBT child devices. However, at >> the same time it added port defaults without further explanation. >> >> Thus, if the child device info was skipped due to multiple child devices >> referencing the same port, the device info would be retrieved from the >> somewhat arbitrary defaults. >> >> Finally, when commit bb1d132935c2 ("drm/i915/vbt: split out defaults >> that are set when there is no VBT") stopped initializing the defaults >> whenever VBT is present, thus trusting the VBT more, we stopped >> initializing ports which were referenced by more than one child device. >> >> Apparently at least Asus UX305UA, UX305U, and UX306U laptops have VBT >> child device blocks which cause this behaviour. Arguably they were >> shipped with a broken VBT. >> >> Relax the rules for multiple references to the same port, and use the >> first child device info to reference a port. Retain the logic to debug >> log about this, though. >> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101745 >> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196233 >> Fixes: bb1d132935c2 ("drm/i915/vbt: split out defaults that are set when there is no VBT") >> Tested-by: Oliver Weißbarth <mail@xxxxxxxxxxxxxx> >> Reported-by: Oliver Weißbarth <mail@xxxxxxxxxxxxxx> >> Reported-by: Didier G <didierg-divers@xxxxxxxxx> >> Reported-by: Giles Anderson <agander@xxxxxxxxx> >> Cc: Manasi Navare <manasi.d.navare@xxxxxxxxx> >> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >> Cc: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx> >> Cc: <stable@xxxxxxxxxxxxxxx> # v4.12+ >> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> >> --- >> drivers/gpu/drm/i915/intel_bios.c | 15 +++++++++------ >> 1 file changed, 9 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c >> index 82b144cdfa1d..183e87e8ea31 100644 >> --- a/drivers/gpu/drm/i915/intel_bios.c >> +++ b/drivers/gpu/drm/i915/intel_bios.c >> @@ -1120,8 +1120,8 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port, >> bool is_dvi, is_hdmi, is_dp, is_edp, is_crt; >> uint8_t aux_channel, ddc_pin; >> /* Each DDI port can have more than one value on the "DVO Port" field, >> - * so look for all the possible values for each port and abort if more >> - * than one is found. */ >> + * so look for all the possible values for each port. >> + */ >> int dvo_ports[][3] = { >> {DVO_PORT_HDMIA, DVO_PORT_DPA, -1}, >> {DVO_PORT_HDMIB, DVO_PORT_DPB, -1}, >> @@ -1130,7 +1130,10 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port, >> {DVO_PORT_CRT, DVO_PORT_HDMIE, DVO_PORT_DPE}, >> }; >> >> - /* Find the child device to use, abort if more than one found. */ >> + /* >> + * Find the first child device to reference the port, report if more >> + * than one found. >> + */ >> for (i = 0; i < dev_priv->vbt.child_dev_num; i++) { >> it = dev_priv->vbt.child_dev + i; >> >> @@ -1140,11 +1143,11 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port, >> >> if (it->common.dvo_port == dvo_ports[port][j]) { >> if (child) { >> - DRM_DEBUG_KMS("More than one child device for port %c in VBT.\n", >> + DRM_DEBUG_KMS("More than one child device for port %c in VBT, using the first.\n", >> port_name(port)); >> - return; > > So the bug here was that in case of port referenced by multiple child devices because it would return from the function, > it would skip the initialization of flags like is_dp/is_hdmi? > It almost feels like they meant to have a break; here instead of return. > Now that this patch removes return it will still iterate through all the chile devices even > after finding second refernce to the same port, isnt that unnecessary? > Would adding a break there instead optimize it? The commit message explicitly says I want to retain the behaviour of flagging the duplicates. There is nothing particularly slow about the loop that needs optimization; debugging machines out the there in the wild is the slow part eating developer time. BR, Jani. > > Regards > Manasi > >> + } else { >> + child = it; >> } >> - child = it; >> } >> } >> } >> -- >> 2.11.0 >> -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx