Re: [PATCH] drm/i915/icl: Fix AUX-B HW not done issue w/o AUX-A

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, May 24, 2019 at 08:35:32PM +0300, Imre Deak wrote:
> Atm AUX-B transfers can fail with the following error if AUX-A is not
> enabled:
> 
> [  594.594108] [drm:intel_dp_aux_xfer [i915]] dp_aux_ch timeout status 0x7c2003ff
> [  594.615854] [drm:intel_dp_aux_xfer [i915]] *ERROR* dp aux hw did not signal timeout!
> [  594.632851] [drm:intel_dp_aux_xfer [i915]] *ERROR* dp aux hw did not signal timeout!
> [  594.632915] [drm:intel_dp_aux_xfer [i915]] *ERROR* dp_aux_ch not done status 0xac2003ff
> [  594.641786] ------------[ cut here ]------------
> [  594.641790] dp_aux_ch not started status 0xac2003ff
> [  594.641874] WARNING: CPU: 4 PID: 1366 at drivers/gpu/drm/i915/intel_dp.c:1268 intel_dp_aux_xfer+0x232/0x890 [i915]
> 
> Ville noticed this issue already earlier and managed to work around it
> by keeping AUX-A always powered whenever AUX-B was used. He also
> reported the issue to HW folks and they have now root caused the problem
> and updated BSpec with a fix (see internal BSpec/Index/21257,
> HSD/1607152412).
> 
> I noticed the same error - even with the WA being applied - while doing
> AUX transfers with Chamelium being connected with a DP cable to the
> source but letting Chamelium imitate an unplug. This is probably some
> unstandard way on Chamelium's behalf of disconnecting itself from the
> AUX pins. For instance it could still pull on the AUX pins which would
> prevent the source from detecting AUX timeouts in the proper way,
> leading to the ERRORs or WARNs seen in the logs in the Reference: bug
> below.
> 
> In case I disconnect the sink properly (the cable itself, not via the
> Chamelium unplug xmlrpc command) then the AUX timeout signaling works
> properly and so there won't be any ERRORs/WARNs emitted.
> 
> Reference: https://bugs.freedesktop.org/show_bug.cgi?id=110718
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/i915_reg.h        | 3 +++
>  drivers/gpu/drm/i915/intel_combo_phy.c | 6 ++++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 87e8780711d7..bae4a2547eb2 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -1846,6 +1846,9 @@ enum i915_power_well_id {
>  #define   VOLTAGE_INFO_MASK		(3 << 24)
>  #define   VOLTAGE_INFO_SHIFT		24
>  
> +#define ICL_PORT_COMP_DW8(port)		_MMIO(_ICL_PORT_COMP_DW(8, port))
> +#define   IREFGEN			(1 << 24)
> +
>  #define CNL_PORT_COMP_DW9		_MMIO(0x162124)
>  #define ICL_PORT_COMP_DW9(port)		_MMIO(_ICL_PORT_COMP_DW(9, port))
>  
> diff --git a/drivers/gpu/drm/i915/intel_combo_phy.c b/drivers/gpu/drm/i915/intel_combo_phy.c
> index 19a9333b727a..98213cc58736 100644
> --- a/drivers/gpu/drm/i915/intel_combo_phy.c
> +++ b/drivers/gpu/drm/i915/intel_combo_phy.c
> @@ -275,6 +275,12 @@ static void icl_combo_phys_init(struct drm_i915_private *dev_priv)
>  
>  		cnl_set_procmon_ref_values(dev_priv, port);
>  
> +		if (port == PORT_A) {
> +			val = I915_READ(ICL_PORT_COMP_DW8(port));
> +			val |= IREFGEN;
> +			I915_WRITE(ICL_PORT_COMP_DW8(port), val);
> +		}
> +
>  		val = I915_READ(ICL_PORT_COMP_DW0(port));
>  		val |= COMP_INIT;
>  		I915_WRITE(ICL_PORT_COMP_DW0(port), val);
> -- 
> 2.17.1

-- 
Ville Syrjälä
Intel
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