Re: [Intel-gfx] [PATCH] drm/i915: Fix type1 DVI DP dual mode adapter heuristic for modern platforms

Jani Nikula
2021-10-27T14:19:23Z

On Wed, 27 Oct 2021, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Tue, Oct 26, 2021 at 02:01:15PM +0300, Jani Nikula wrote:
>> On Mon, 25 Oct 2021, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
>> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> >
>> > Looks like we never updated intel_bios_is_port_dp_dual_mode() when
>> > the VBT port mapping became erratic on modern platforms. This
>> > is causing us to look up the wrong child device and thus throwing
>> > the heuristic off (ie. we might end looking at a child device for
>> > a genuine DP++ port when we were supposed to look at one for a
>> > native HDMI port).
>> >
>> > Fix it up by not using the outdated port_mapping[] in
>> > intel_bios_is_port_dp_dual_mode() and rely on
>> > intel_bios_encoder_data_lookup() instead.
>>
>> It's just crazy, we have like 7 port_mapping tables in intel_bios.c,
>> what happened?!
>>
>> I wish we could unify all of this more.
>>
>> >
>> > Cc: stable@vger.kernel.org
>> > Tested-by: Randy Dunlap <rdunlap@infradead.org>
>> > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4138
>> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> > ---
>> > drivers/gpu/drm/i915/display/intel_bios.c | 85 +++++++++++++++++------
>> > 1 file changed, 63 insertions(+), 22 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
>> > index f9776ca85de3..2b1423a43437 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_bios.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_bios.c
>> > @@ -1707,6 +1707,39 @@ static void sanitize_aux_ch(struct intel_bios_encoder_data *devdata,
>> > child->aux_channel = 0;
>> > }
>> >
>> > +static u8 dvo_port_type(u8 dvo_port)
>> > +{
>> > + switch (dvo_port) {
>> > + case DVO_PORT_HDMIA:
>> > + case DVO_PORT_HDMIB:
>> > + case DVO_PORT_HDMIC:
>> > + case DVO_PORT_HDMID:
>> > + case DVO_PORT_HDMIE:
>> > + case DVO_PORT_HDMIF:
>> > + case DVO_PORT_HDMIG:
>> > + case DVO_PORT_HDMIH:
>> > + case DVO_PORT_HDMII:
>> > + return DVO_PORT_HDMIA;
>> > + case DVO_PORT_DPA:
>> > + case DVO_PORT_DPB:
>> > + case DVO_PORT_DPC:
>> > + case DVO_PORT_DPD:
>> > + case DVO_PORT_DPE:
>> > + case DVO_PORT_DPF:
>> > + case DVO_PORT_DPG:
>> > + case DVO_PORT_DPH:
>> > + case DVO_PORT_DPI:
>> > + return DVO_PORT_DPA;
>> > + case DVO_PORT_MIPIA:
>> > + case DVO_PORT_MIPIB:
>> > + case DVO_PORT_MIPIC:
>> > + case DVO_PORT_MIPID:
>> > + return DVO_PORT_MIPIA;
>> > + default:
>> > + return dvo_port;
>> > + }
>> > +}
>> > +
>> > static enum port __dvo_port_to_port(int n_ports, int n_dvo,
>> > const int port_mapping[][3], u8 dvo_port)
>> > {
>> > @@ -2623,35 +2656,17 @@ bool intel_bios_is_port_edp(struct drm_i915_private *i915, enum port port)
>> > return false;
>> > }
>> >
>> > -static bool child_dev_is_dp_dual_mode(const struct child_device_config *child,
>> > - enum port port)
>> > +static bool child_dev_is_dp_dual_mode(const struct child_device_config *child)
>> > {
>> > - static const struct {
>> > - u16 dp, hdmi;
>> > - } port_mapping[] = {
>> > - /*
>> > - * Buggy VBTs may declare DP ports as having
>> > - * HDMI type dvo_port :( So let's check both.
>> > - */
>> > - [PORT_B] = { DVO_PORT_DPB, DVO_PORT_HDMIB, },
>> > - [PORT_C] = { DVO_PORT_DPC, DVO_PORT_HDMIC, },
>> > - [PORT_D] = { DVO_PORT_DPD, DVO_PORT_HDMID, },
>> > - [PORT_E] = { DVO_PORT_DPE, DVO_PORT_HDMIE, },
>> > - [PORT_F] = { DVO_PORT_DPF, DVO_PORT_HDMIF, },
>> > - };
>> > -
>> > - if (port == PORT_A || port >= ARRAY_SIZE(port_mapping))
>> > - return false;
>> > -
>> > if ((child->device_type & DEVICE_TYPE_DP_DUAL_MODE_BITS) !=
>> > (DEVICE_TYPE_DP_DUAL_MODE & DEVICE_TYPE_DP_DUAL_MODE_BITS))
>> > return false;
>> >
>> > - if (child->dvo_port == port_mapping[port].dp)
>> > + if (dvo_port_type(child->dvo_port) == DVO_PORT_DPA)
>> > return true;
>>
>> I wonder, why do we care about dvo_port here, while we ignore the dvo
>> port DP/HDMI/DSI difference in parse_ddi_port()? I'm not really entirely
>> happy about adding another dvo port check method. :/
>
> Because VBTs suck and sometimes a DP++ port is declared as DP (as
> it should) but sometimes it's declared as HDMI instead. Hence the
> additional "do we has aux ch?" check for the dvo_port==HDMI case to
> make it at least try not to match native HDMI ports. I'm not sure
> whether we could just always do the AUX CH check and ignore the
> dvo_port entirely. Would need to look through a bunch of VBTs to
> get some idea I suppose. But that would be too much change for a
> bugfix anyway.
>
> IIRC the other idea of just looking at the device_type bits was a
> bust on at least vlv/chv.

*sad trombone*

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

The bikeshedding is that I think we should convert
child_dev_is_dp_dual_mode() to the same style as the other
intel_bios_encoder_supports_*() functions. And we could add the dual
mode in "Port %c VBT info" logging in parse_ddi_port() too.

In the long run I'd like to ensure encoder->devdata is non-NULL and
valid for more platforms, so we could just call
intel_bios_encoder_supports_dual_mode(encoder->devdata) directly, so we
don't have to loop over ports every time.

Anyway, all of this is just musing for future, can be follow-up.

BR,
Jani.

>
>>
>> >
>> > /* Only accept a HDMI dvo_port as DP++ if it has an AUX channel */
>> > - if (child->dvo_port == port_mapping[port].hdmi &&
>> > + if (dvo_port_type(child->dvo_port) == DVO_PORT_HDMIA &&
>> > child->aux_channel != 0)
>> > return true;
>> >
>> > @@ -2661,10 +2676,36 @@ static bool child_dev_is_dp_dual_mode(const struct child_device_config *child,
>> > bool intel_bios_is_port_dp_dual_mode(struct drm_i915_private *i915,
>> > enum port port)
>> > {
>> > + static const struct {
>> > + u16 dp, hdmi;
>> > + } port_mapping[] = {
>> > + /*
>> > + * Buggy VBTs may declare DP ports as having
>> > + * HDMI type dvo_port :( So let's check both.
>> > + */
>> > + [PORT_B] = { DVO_PORT_DPB, DVO_PORT_HDMIB, },
>> > + [PORT_C] = { DVO_PORT_DPC, DVO_PORT_HDMIC, },
>> > + [PORT_D] = { DVO_PORT_DPD, DVO_PORT_HDMID, },
>> > + [PORT_E] = { DVO_PORT_DPE, DVO_PORT_HDMIE, },
>> > + [PORT_F] = { DVO_PORT_DPF, DVO_PORT_HDMIF, },
>> > + };
>> > const struct intel_bios_encoder_data *devdata;
>> >
>> > + if (HAS_DDI(i915)) {
>> > + const struct intel_bios_encoder_data *devdata;
>> > +
>> > + devdata = intel_bios_encoder_data_lookup(i915, port);
>> > +
>> > + return devdata && child_dev_is_dp_dual_mode(&devdata->child);
>> > + }
>> > +
>> > + if (port == PORT_A || port >= ARRAY_SIZE(port_mapping))
>> > + return false;
>> > +
>> > list_for_each_entry(devdata, &i915->vbt.display_devices, node) {
>> > - if (child_dev_is_dp_dual_mode(&devdata->child, port))
>> > + if ((devdata->child.dvo_port == port_mapping[port].dp ||
>> > + devdata->child.dvo_port == port_mapping[port].hdmi) &&
>> > + child_dev_is_dp_dual_mode(&devdata->child))
>> > return true;
>> > }
>>
>> --
>> Jani Nikula, Intel Open Source Graphics Center

--
Jani Nikula, Intel Open Source Graphics Center