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 17:25, Dmitry Baryshkov wrote:
> 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.

After another glance it still looks good to me. Please send the last 
iteration of the series:
- moving all core patches to the first place, as it was asked 
previously. This will help us get them merged to drm core repo first
- dropping the patch 09 as agreed.

-- 
With best wishes
Dmitry