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

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

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