[Intel-gfx] [PATCH] drm/i915/display: Skip state verification with TBT-ALT mode

[Gustavo Sousa]

Quoting Jani Nikula (2023-11-27 13:47:22-03:00)
>On Mon, 27 Nov 2023, Mika Kahola <mika.kahola at intel.com> wrote:
>> With TBT-ALT mode we are not programming C20 chip PLL's and
>> hence we don't need to check state verification. We don't
>> need to program DP link signal levels i.e.pre-emphasis and
>> voltage swing either.
>>
>> This patch fixes dmesg errors like this one
>>
>> "[drm] ERROR PHY F Write 0c06 failed after 3 retries."
>>
>> Signed-off-by: Mika Kahola <mika.kahola at intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_cx0_phy.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_cx0_phy.c b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
>> index a8fa76580802..3a30cffd450c 100644
>> --- a/drivers/gpu/drm/i915/display/intel_cx0_phy.c
>> +++ b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
>> @@ -418,6 +418,10 @@ void intel_cx0_phy_set_signal_levels(struct intel_encoder *encoder,
>>          u8 owned_lane_mask = intel_cx0_get_owned_lane_mask(i915, encoder);
>>          intel_wakeref_t wakeref;
>>          int n_entries, ln;
>> +        struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
>> +
>> +        if (intel_tc_port_in_tbt_alt_mode(dig_port))
>> +                return;
>>  
>>          wakeref = intel_cx0_phy_transaction_begin(encoder);
>>  
>> @@ -3136,6 +3140,9 @@ void intel_cx0pll_state_verify(struct intel_atomic_state *state,
>>          encoder = intel_get_crtc_new_encoder(state, new_crtc_state);
>>          phy = intel_port_to_phy(i915, encoder->port);
>>  
>> +        if (intel_tc_port_in_tbt_alt_mode(enc_to_dig_port(encoder)))
>> +                return;
>> +
>
>Shouldn't we read and ensure it's disabled?

In TBT-alt mode, the PHY is owned by the Thunderbold controller, and it could be
in use.

I guess what we could do is verify that PORT_CLOCK_CTL has the expected bits
depending on the mode. That could done here or in a followup series.

--
Gustavo Sousa

>
>>          intel_cx0pll_readout_hw_state(encoder, &mpll_hw_state);
>>  
>>          if (intel_is_c10phy(i915, phy))
>
>-- 
>Jani Nikula, Intel