Re: [PATCH v12 13/14] drm/msm/disp/dpu: add PSR support for eDP interface in dpu driver

[Dmitry Baryshkov]

On 07/02/2023 16:26, Vinod Polimera wrote:
> > -----Original Message-----
> > From: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > Sent: Tuesday, January 31, 2023 6:29 PM
> > To: Vinod Polimera (QUIC) <quic_vpolimer@xxxxxxxxxxx>; dri-
> > devel@xxxxxxxxxxxxxxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx;
> > freedreno@xxxxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx; robdclark@xxxxxxxxx;
> > dianders@xxxxxxxxxxxx; swboyd@xxxxxxxxxxxx; Kalyan Thota (QUIC)
> > <quic_kalyant@xxxxxxxxxxx>; Kuogee Hsieh (QUIC)
> > <quic_khsieh@xxxxxxxxxxx>; Vishnuvardhan Prodduturi (QUIC)
> > <quic_vproddut@xxxxxxxxxxx>; Bjorn Andersson (QUIC)
> > <quic_bjorande@xxxxxxxxxxx>; Abhinav Kumar (QUIC)
> > <quic_abhinavk@xxxxxxxxxxx>; Sankeerth Billakanti (QUIC)
> > <quic_sbillaka@xxxxxxxxxxx>
> > Subject: Re: [PATCH v12 13/14] drm/msm/disp/dpu: add PSR support for eDP
> > interface in dpu driver
> >
> >
> > On 30/01/2023 17:11, Vinod Polimera wrote:
> > > Enable PSR on eDP interface using drm self-refresh librabry.
> > > This patch uses a trigger from self-refresh library to enter/exit
> > > into PSR, when there are no updates from framework.
> > >
> > > Signed-off-by: Kalyan Thota <quic_kalyant@xxxxxxxxxxx>
> > > Signed-off-by: Vinod Polimera <quic_vpolimer@xxxxxxxxxxx>
> > > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > > ---
> > >    drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c    | 13 ++++++++++++-
> > >    drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 14 ++++++++++++++
> > >    drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c     |  2 +-
> > >    3 files changed, 27 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > > index f29a339..60e5984 100644
> > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > > @@ -21,6 +21,7 @@
> > >    #include <drm/drm_probe_helper.h>
> > >    #include <drm/drm_rect.h>
> > >    #include <drm/drm_vblank.h>
> > > +#include <drm/drm_self_refresh_helper.h>
> > >
> > >    #include "dpu_kms.h"
> > >    #include "dpu_hw_lm.h"
> > > @@ -1021,6 +1022,9 @@ static void dpu_crtc_disable(struct drm_crtc *crtc,
> > >
> > >        DRM_DEBUG_KMS("crtc%d\n", crtc->base.id);
> > >
> > > +     if (old_crtc_state->self_refresh_active)
> > > +             return;
> > > +
> >
> > I have been looking at the crtc_needs_disable(). It explicitly mentions
> > that 'We also need to run through the crtc_funcs->disable() function
> > [..] if it's transitioning to self refresh mode...'. Don't we need to
> > perform some cleanup here (like disabling the vblank irq handling,
> > freeing the bandwidth, etc)?
>
> When self refresh active is enabled, then we will clean up irq handling and bandwidth etc.
> The above case is to handle display off commit triggered when we are in psr as all
>   the resources are already cleaned up . we just need to do an early return.
> > >        /* Disable/save vblank irq handling */
> > >        drm_crtc_vblank_off(crtc);
> > >
> > > @@ -1577,7 +1581,7 @@ struct drm_crtc *dpu_crtc_init(struct drm_device
> > *dev, struct drm_plane *plane,
> > >    {
> > >        struct drm_crtc *crtc = NULL;
> > >        struct dpu_crtc *dpu_crtc = NULL;
> > > -     int i;
> > > +     int i, ret;
> > >
> > >        dpu_crtc = kzalloc(sizeof(*dpu_crtc), GFP_KERNEL);
> > >        if (!dpu_crtc)
> > > @@ -1614,6 +1618,13 @@ struct drm_crtc *dpu_crtc_init(struct
> > drm_device *dev, struct drm_plane *plane,
> > >        /* initialize event handling */
> > >        spin_lock_init(&dpu_crtc->event_lock);
> > >
> > > +     ret = drm_self_refresh_helper_init(crtc);
> > > +     if (ret) {
> > > +             DPU_ERROR("Failed to initialize %s with self-refresh helpers %d\n",
> > > +                     crtc->name, ret);
> > > +             return ERR_PTR(ret);
> > > +     }
> > > +
> > >        DRM_DEBUG_KMS("%s: successfully initialized crtc\n", dpu_crtc-
> > > name);
> > >        return crtc;
> > >    }
> > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > > index 01b7509..450abb1 100644
> > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > > @@ -12,6 +12,7 @@
> > >    #include <linux/kthread.h>
> > >    #include <linux/seq_file.h>
> > >
> > > +#include <drm/drm_atomic.h>
> > >    #include <drm/drm_crtc.h>
> > >    #include <drm/drm_file.h>
> > >    #include <drm/drm_probe_helper.h>
> > > @@ -1212,11 +1213,24 @@ static void
> > dpu_encoder_virt_atomic_disable(struct drm_encoder *drm_enc,
> > >                                        struct drm_atomic_state *state)
> > >    {
> > >        struct dpu_encoder_virt *dpu_enc = NULL;
> > > +     struct drm_crtc *crtc;
> > > +     struct drm_crtc_state *old_state = NULL;
> > >        int i = 0;
> > >
> > >        dpu_enc = to_dpu_encoder_virt(drm_enc);
> > >        DPU_DEBUG_ENC(dpu_enc, "\n");
> > >
> > > +     crtc = drm_atomic_get_old_crtc_for_encoder(state, drm_enc);
> > > +     if (crtc)
> > > +             old_state = drm_atomic_get_old_crtc_state(state, crtc);
> > > +
> > > +     /*
> > > +      * The encoder is already disabled if self refresh mode was set earlier,
> > > +      * in the old_state for the corresponding crtc.
> > > +      */
> > > +     if (old_state && old_state->self_refresh_active)
> > > +             return;
> > > +
> >
> > Again the same question here, doesn't crtc_needs_disable() take care of
> > this clause? I might be missing something in the PSR state transitions.
> > Could you please add some explanation here?
> Same usecase as above, applies to encoder disable also when triggered via disable commit
> When driver is in psr state.

Ack, thank you for the explanations. I'd like to take another glance 
later today, but generally it look good to me.

--
With best wishes
Dmitry