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

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Date:   Tue, 31 Jan 2023 14:58:47 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Vinod Polimera <quic_vpolimer@...cinc.com>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, robdclark@...il.com,
        dianders@...omium.org, swboyd@...omium.org,
        quic_kalyant@...cinc.com, quic_khsieh@...cinc.com,
        quic_vproddut@...cinc.com, quic_bjorande@...cinc.com,
        quic_abhinavk@...cinc.com, quic_sbillaka@...cinc.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@...cinc.com>
> Signed-off-by: Vinod Polimera <quic_vpolimer@...cinc.com>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.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)?

>   	/* 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?

>   	mutex_lock(&dpu_enc->enc_lock);
>   	dpu_enc->enabled = false;
>   
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index a683bd9..681dd2e 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -491,7 +491,7 @@ static void dpu_kms_wait_for_commit_done(struct msm_kms *kms,
>   		return;
>   	}
>   
> -	if (!crtc->state->active) {
> +	if (!drm_atomic_crtc_effectively_active(crtc->state)) {
>   		DPU_DEBUG("[crtc:%d] not active\n", crtc->base.id);
>   		return;
>   	}

-- 
With best wishes
Dmitry