[PATCH v2 19/23] drm/amd/display: Add debug flags for USB4 DP link training

[Lin, Wayne]

[Public]

> -----Original Message-----
> From: Wentland, Harry <Harry.Wentland at amd.com>
> Sent: Wednesday, October 6, 2021 1:11 AM
> To: Lin, Wayne <Wayne.Lin at amd.com>; amd-gfx at lists.freedesktop.org
> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Kazlauskas, Nicholas <Nicholas.Kazlauskas at amd.com>; Siqueira, Rodrigo
> <Rodrigo.Siqueira at amd.com>; Wang, Chao-kai (Stylon) <Stylon.Wang at amd.com>; Shih, Jude <Jude.Shih at amd.com>; Kizito, Jimmy
> <Jimmy.Kizito at amd.com>; Somasundaram, Meenakshikumar <Meenakshikumar.Somasundaram at amd.com>; Lei, Jun <Jun.Lei at amd.com>
> Subject: Re: [PATCH v2 19/23] drm/amd/display: Add debug flags for USB4 DP link training
>
>
>
> On 2021-10-05 03:52, Wayne Lin wrote:
> > From: Jimmy Kizito <Jimmy.Kizito at amd.com>
> >
> > [Why & How]
> > Additional debug flags that can be useful for testing USB4 DP link
> > training.
> >
> > Add flags:
> > - 0x2 : Forces USB4 DP link to non-LTTPR mode
> > - 0x4 : Extends status read intervals to about 60s.
> >
> > Reviewed-by: Meenakshikumar Somasundaram
> > <meenakshikumar.somasundaram at amd.com>
> > Reviewed-by: Jun Lei <Jun.Lei at amd.com>
> > Acked-by: Wayne Lin <Wayne.Lin at amd.com>
> > Acked-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
> > Signed-off-by: Jimmy Kizito <Jimmy.Kizito at amd.com>
> > ---
> >  drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c   | 6 ++++++
> >  drivers/gpu/drm/amd/display/dc/core/dc_link_dpia.c | 6 ++++++
> >  drivers/gpu/drm/amd/display/dc/dc.h                | 4 +++-
> >  drivers/gpu/drm/amd/display/dc/inc/dc_link_dpia.h  | 3 +++
> >  4 files changed, 18 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> > b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> > index bfba1d2c6a18..423fbd2b9b39 100644
> > --- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> > +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> > @@ -4528,6 +4528,12 @@ bool dp_retrieve_lttpr_cap(struct dc_link *link)
> >             else
> >                     link->lttpr_mode = LTTPR_MODE_NON_TRANSPARENT;
> >     }
> > +#if defined(CONFIG_DRM_AMD_DC_DCN)
>
> Why is this guarded with DC_DCN when all other DPIA code isn't?
> It looks like it might be unnecessary.
Thanks Harry.

Since declaration of dpia_debug variable is guarded by CONFIG_DRM_AMD_DC_DCN,
we should keep this here.

Thanks!
>
> > +   /* Check DP tunnel LTTPR mode debug option. */
> > +   if (link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA &&
> > +       link->dc->debug.dpia_debug.bits.force_non_lttpr)
> > +           link->lttpr_mode = LTTPR_MODE_NON_LTTPR; #endif
> >
> >     if (link->lttpr_mode == LTTPR_MODE_NON_TRANSPARENT || link->lttpr_mode == LTTPR_MODE_TRANSPARENT) {
> >             /* By reading LTTPR capability, RX assumes that we will enable diff
> > --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dpia.c
> > b/drivers/gpu/drm/amd/display/dc/core/dc_link_dpia.c
> > index 7407c755a73e..ce15a38c2aea 100644
> > --- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dpia.c
> > +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dpia.c
> > @@ -528,6 +528,12 @@ static uint32_t dpia_get_eq_aux_rd_interval(const struct dc_link *link,
> >                             dp_translate_training_aux_read_interval(
> >                                     link->dpcd_caps.lttpr_caps.aux_rd_interval[hop - 1]);
> >
> > +#if defined(CONFIG_DRM_AMD_DC_DCN)
>
> Same here. Please drop this guard if we don't need it.
>
> Harry
>
> > +   /* Check debug option for extending aux read interval. */
> > +   if (link->dc->debug.dpia_debug.bits.extend_aux_rd_interval)
> > +           wait_time_microsec = DPIA_DEBUG_EXTENDED_AUX_RD_INTERVAL_US;
> > +#endif
> > +
> >     return wait_time_microsec;
> >  }
> >
> > diff --git a/drivers/gpu/drm/amd/display/dc/dc.h
> > b/drivers/gpu/drm/amd/display/dc/dc.h
> > index e3f884942e04..86fa94a2ef48 100644
> > --- a/drivers/gpu/drm/amd/display/dc/dc.h
> > +++ b/drivers/gpu/drm/amd/display/dc/dc.h
> > @@ -499,7 +499,9 @@ union root_clock_optimization_options {  union
> > dpia_debug_options {
> >     struct {
> >             uint32_t disable_dpia:1;
> > -           uint32_t reserved:31;
> > +           uint32_t force_non_lttpr:1;
> > +           uint32_t extend_aux_rd_interval:1;
> > +           uint32_t reserved:29;
> >     } bits;
> >     uint32_t raw;
> >  };
> > diff --git a/drivers/gpu/drm/amd/display/dc/inc/dc_link_dpia.h
> > b/drivers/gpu/drm/amd/display/dc/inc/dc_link_dpia.h
> > index 790b904e37e1..e3dfe4c89ce0 100644
> > --- a/drivers/gpu/drm/amd/display/dc/inc/dc_link_dpia.h
> > +++ b/drivers/gpu/drm/amd/display/dc/inc/dc_link_dpia.h
> > @@ -34,6 +34,9 @@ struct dc_link_settings;
> >  /* The approximate time (us) it takes to transmit 9 USB4 DP clock
> > sync packets. */  #define DPIA_CLK_SYNC_DELAY 16000
> >
> > +/* Extend interval between training status checks for manual testing.
> > +*/ #define DPIA_DEBUG_EXTENDED_AUX_RD_INTERVAL_US 60000000
> > +
> >  /** @note Can remove once DP tunneling registers in upstream
> > include/drm/drm_dp_helper.h */
> >  /* DPCD DP Tunneling over USB4 */
> >  #define DP_TUNNELING_CAPABILITIES_SUPPORT 0xe000d
> >
--
Regards,
Wayne