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    SubjectRe: [PATCH v12 13/14] drm/msm/disp/dpu: add PSR support for eDP interface in dpu driver
    From
    On 07/02/2023 16:26, Vinod Polimera wrote:
    >
    >
    >> -----Original Message-----
    >> From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
    >> Sent: Tuesday, January 31, 2023 6:29 PM
    >> To: Vinod Polimera (QUIC) <quic_vpolimer@quicinc.com>; dri-
    >> devel@lists.freedesktop.org; linux-arm-msm@vger.kernel.org;
    >> freedreno@lists.freedesktop.org; devicetree@vger.kernel.org
    >> Cc: linux-kernel@vger.kernel.org; robdclark@gmail.com;
    >> dianders@chromium.org; swboyd@chromium.org; Kalyan Thota (QUIC)
    >> <quic_kalyant@quicinc.com>; Kuogee Hsieh (QUIC)
    >> <quic_khsieh@quicinc.com>; Vishnuvardhan Prodduturi (QUIC)
    >> <quic_vproddut@quicinc.com>; Bjorn Andersson (QUIC)
    >> <quic_bjorande@quicinc.com>; Abhinav Kumar (QUIC)
    >> <quic_abhinavk@quicinc.com>; Sankeerth Billakanti (QUIC)
    >> <quic_sbillaka@quicinc.com>
    >> 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@quicinc.com>
    >>> Signed-off-by: Vinod Polimera <quic_vpolimer@quicinc.com>
    >>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
    >>> ---
    >>> 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

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