Re: [PATCH v2 02/38] drm/msm/dp: remove dp_display's dp_mode and use dp_panel's instead

[Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>]

On 27/06/2025 11:40, Yongxing Mou wrote:
> 
> 
> On 2025/6/25 22:03, Dmitry Baryshkov wrote:
>> On Wed, Jun 25, 2025 at 08:34:18PM +0800, Yongxing Mou wrote:
>>>
>>>
>>> On 2025/6/9 20:48, Dmitry Baryshkov wrote:
>>>> On Mon, Jun 09, 2025 at 08:21:21PM +0800, Yongxing Mou wrote:
>>>>> From: Abhinav Kumar <quic_abhinavk@quicinc.com>
>>>>>
>>>>> dp_display caches the current display mode and then passes it onto
>>>>> the panel to be used for programming the panel params. Remove this
>>>>> two level passing and directly populated the panel's dp_display_mode
>>>>> instead.
>>>>
>>>> - Why do we need to cache / copy it anyway? Can't we just pass the
>>>>     corresponding drm_atomic_state / drm_crtc_state / 
>>>> drm_display_mode ?
>>>>
>>> This part works as follows: .mode_set() copies the adjusted_mode into
>>> msm_dp_display_private->msm_dp_display_mode, and also parses and stores
>>> variables such as v_active_low/h_active_low/out_fmt_is_yuv_420 
>>> and ... When
>>> @drm_bridge_funcs.atomic_enable() is called, it copies
>>> msm_dp_display->msm_dp_mode into dp_panel->msm_dp_mode and initializes
>>> panel_info in msm_dp_display_set_mode(). Then when go to
>>> msm_dp_ctrl_on_stream(), the parameters are updated into the 
>>> corresponding
>>> hardware registers.
>>
>> So, if we do everything during .atomic_enable(), there would be no need
>> to store and/or copy anything. All the data is available and can be used
>> as is.
>>
> Got it. Let me confirm—can we keep msm_dp_mode or drm_display_mode in 
> msm_dp_panel? Mabey debug node will use this ..

Please don't. I really dislike storing drm_atomic_state-related 
variables in a non-state structure. I think it makes it easier to 
mistakenly update or to use a stale value.

Debug code already prints modes in debugfs/dri/N/state. If we need any 
other state-related prints, they should go to the same file.

>>>
>>> This design has been in place since the first version of the DP 
>>> driver and
>>> has remained largely unchanged.
>>
>> Yes... The point is that you are touching this piece of code anyway,
>> let's make it nicer.
>>
> Agree with this point.
>>> Originally, the drm_mode would be passed in
>>> two stages: from msm_dp_display->msm_dp_mode to dp_panel- 
>>> >msm_dp_mode. Since
>>> in MST mode each stream requires its own drm_mode and stored in 
>>> dp_panel, we
>>> simplified the two-stage transfer into a single step (.mode_set() do all
>>> things and store in msm_dp_panel). Meanwhile we modified the
>>> msm_dp_display_set_mode function to accept a msm_dp_panel parameter,
>>> allowing the MST bridge funcs' mode_set() to reuse this part code.
>>>
>>> The following patches:
>>> https://patchwork.freedesktop.org/patch/657573/?series=142207&rev=2 and
>>> https://patchwork.freedesktop.org/patch/657593/?series=142207&rev=2,
>>> introduce msm_dp_display_*_helper functions to help reuse common code 
>>> across
>>> MST/SST/eDP drm_bridge_funcs.
>>>
>>> If we drop msm_dp_mode from dp_panel and use drm_display_mode, it might
>>> introduce a large number of changes that are not directly related to 
>>> MST.
>>> Actually i think the presence of msm_dp_display_mode seems to 
>>> simplify the
>>> work in msm_dp_panel_timing_cfg(), this patch series we want to focus 
>>> on MST
>>> parts, so would we consider optimizing them later?
>>
>> Sure... But then you have to change two places. If you optimize it
>> first, you have to touch only place. And it can be even submitted
>> separately.
>>
> Understood, that’s indeed the case. I just want to prioritize the MST 
> patch and have it merged first, since it involves changes to lots of 
> files. Thanks~~
>>>
>>> Thanks~
>>>>>
>>>>> Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
>>>>> Signed-off-by: Yongxing Mou <quic_yongmou@quicinc.com>
>>>>> ---
>>>>>    drivers/gpu/drm/msm/dp/dp_display.c | 76 +++++++++++++ 
>>>>> +-----------------------
>>>>>    1 file changed, 29 insertions(+), 47 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/ 
>>>>> msm/dp/dp_display.c
>>>>> index 
>>>>> 4a9b65647cdef1ed6c3bb851f93df0db8be977af..9d2db9cbd2552470a36a63f70f517c35436f7280 100644
>>>>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>>>>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>>>>> @@ -92,7 +92,6 @@ struct msm_dp_display_private {
>>>>>        struct msm_dp_panel   *panel;
>>>>>        struct msm_dp_ctrl    *ctrl;
>>>>> -    struct msm_dp_display_mode msm_dp_mode;
>>>>>        struct msm_dp msm_dp_display;
>>>>>        /* wait for audio signaling */
>>>>> @@ -806,16 +805,29 @@ static int msm_dp_init_sub_modules(struct 
>>>>> msm_dp_display_private *dp)
>>>>>    }
>>>>>    static int msm_dp_display_set_mode(struct msm_dp *msm_dp_display,
>>>>> -                   struct msm_dp_display_mode *mode)
>>>>> +                   const struct drm_display_mode *adjusted_mode,
>>>>> +                   struct msm_dp_panel *msm_dp_panel)
>>>>>    {
>>>>> -    struct msm_dp_display_private *dp;
>>>>> +    u32 bpp;
>>>>> -    dp = container_of(msm_dp_display, struct 
>>>>> msm_dp_display_private, msm_dp_display);
>>>>> +    drm_mode_copy(&msm_dp_panel->msm_dp_mode.drm_mode, 
>>>>> adjusted_mode);
>>>>> +
>>>>> +    if (msm_dp_display_check_video_test(msm_dp_display))
>>>>> +        bpp = msm_dp_display_get_test_bpp(msm_dp_display);
>>>>> +    else
>>>>> +        bpp = msm_dp_panel->connector->display_info.bpc * 3;
>>>>> +
>>>>> +    msm_dp_panel->msm_dp_mode.bpp = bpp;
>>>>> +
>>>>> +    msm_dp_panel->msm_dp_mode.v_active_low =
>>>>> +        !!(adjusted_mode->flags & DRM_MODE_FLAG_NVSYNC);
>>>>> +    msm_dp_panel->msm_dp_mode.h_active_low =
>>>>> +        !!(adjusted_mode->flags & DRM_MODE_FLAG_NHSYNC);
>>>>> +    msm_dp_panel->msm_dp_mode.out_fmt_is_yuv_420 =
>>>>> +        drm_mode_is_420_only(&msm_dp_panel->connector- 
>>>>> >display_info, adjusted_mode) &&
>>>>> +        msm_dp_panel->vsc_sdp_supported;
>>>>> -    drm_mode_copy(&dp->panel->msm_dp_mode.drm_mode, &mode->drm_mode);
>>>>> -    dp->panel->msm_dp_mode.bpp = mode->bpp;
>>>>> -    dp->panel->msm_dp_mode.out_fmt_is_yuv_420 = mode- 
>>>>> >out_fmt_is_yuv_420;
>>>>> -    msm_dp_panel_init_panel_info(dp->panel);
>>>>> +    msm_dp_panel_init_panel_info(msm_dp_panel);
>>>>>        return 0;
>>>>>    }
>>>>> @@ -1431,10 +1443,13 @@ bool msm_dp_needs_periph_flush(const struct 
>>>>> msm_dp *msm_dp_display,
>>>>>    bool msm_dp_wide_bus_available(const struct msm_dp *msm_dp_display)
>>>>>    {
>>>>>        struct msm_dp_display_private *dp;
>>>>> +    struct msm_dp_panel *dp_panel;
>>>>>        dp = container_of(msm_dp_display, struct 
>>>>> msm_dp_display_private, msm_dp_display);
>>>>> -    if (dp->msm_dp_mode.out_fmt_is_yuv_420)
>>>>> +    dp_panel = dp->panel;
>>>>> +
>>>>> +    if (dp_panel->msm_dp_mode.out_fmt_is_yuv_420)
>>>>>            return false;
>>>>>        return dp->wide_bus_supported;
>>>>> @@ -1496,10 +1511,6 @@ void msm_dp_bridge_atomic_enable(struct 
>>>>> drm_bridge *drm_bridge,
>>>>>        bool force_link_train = false;
>>>>>        msm_dp_display = container_of(dp, struct 
>>>>> msm_dp_display_private, msm_dp_display);
>>>>> -    if (!msm_dp_display->msm_dp_mode.drm_mode.clock) {
>>>>> -        DRM_ERROR("invalid params\n");
>>>>> -        return;
>>>>> -    }
>>>>>        if (dp->is_edp)
>>>>>            msm_dp_hpd_plug_handle(msm_dp_display, 0);
>>>>> @@ -1517,15 +1528,6 @@ void msm_dp_bridge_atomic_enable(struct 
>>>>> drm_bridge *drm_bridge,
>>>>>            return;
>>>>>        }
>>>>> -    rc = msm_dp_display_set_mode(dp, &msm_dp_display->msm_dp_mode);
>>>>> -    if (rc) {
>>>>> -        DRM_ERROR("Failed to perform a mode set, rc=%d\n", rc);
>>>>> -        mutex_unlock(&msm_dp_display->event_mutex);
>>>>> -        return;
>>>>> -    }
>>>>
>>>> It should be done other way around: keep this call and drop
>>>> msm_dp_bridge_mode_set().
>>>>
>>> Emm as reply in last comments..
>>
>> Yep. Drop .mode_set, the callback is even described as deprecated.
>>
> Thanks, the documentation does state that.
>>>>> -
>>>>> -    hpd_state =  msm_dp_display->hpd_state;
>>>>> -
>>>>>        if (hpd_state == ST_CONNECTED && !dp->power_on) {
>>>>>            msm_dp_display_host_phy_init(msm_dp_display);
>>>>>            force_link_train = true;
>>>>> @@ -1604,33 +1606,13 @@ void msm_dp_bridge_mode_set(struct 
>>>>> drm_bridge *drm_bridge,
>>>>>        msm_dp_display = container_of(dp, struct 
>>>>> msm_dp_display_private, msm_dp_display);
>>>>>        msm_dp_panel = msm_dp_display->panel;
>>>>> -    memset(&msm_dp_display->msm_dp_mode, 0x0, sizeof(struct 
>>>>> msm_dp_display_mode));
>>>>> -
>>>>> -    if (msm_dp_display_check_video_test(dp))
>>>>> -        msm_dp_display->msm_dp_mode.bpp = 
>>>>> msm_dp_display_get_test_bpp(dp);
>>>>> -    else /* Default num_components per pixel = 3 */
>>>>> -        msm_dp_display->msm_dp_mode.bpp = dp->connector- 
>>>>> >display_info.bpc * 3;
>>>>> -
>>>>> -    if (!msm_dp_display->msm_dp_mode.bpp)
>>>>> -        msm_dp_display->msm_dp_mode.bpp = 24; /* Default bpp */
>>>>> -
>>>>> -    drm_mode_copy(&msm_dp_display->msm_dp_mode.drm_mode, 
>>>>> adjusted_mode);
>>>>> -
>>>>> -    msm_dp_display->msm_dp_mode.v_active_low =
>>>>> -        !!(msm_dp_display->msm_dp_mode.drm_mode.flags & 
>>>>> DRM_MODE_FLAG_NVSYNC);
>>>>> -
>>>>> -    msm_dp_display->msm_dp_mode.h_active_low =
>>>>> -        !!(msm_dp_display->msm_dp_mode.drm_mode.flags & 
>>>>> DRM_MODE_FLAG_NHSYNC);
>>>>> -
>>>>> -    msm_dp_display->msm_dp_mode.out_fmt_is_yuv_420 =
>>>>> -        drm_mode_is_420_only(&dp->connector->display_info, 
>>>>> adjusted_mode) &&
>>>>> -        msm_dp_panel->vsc_sdp_supported;
>>>>> +    msm_dp_display_set_mode(dp, adjusted_mode, msm_dp_panel);
>>>>>        /* populate wide_bus_support to different layers */
>>>>> -    msm_dp_display->ctrl->wide_bus_en =
>>>>> -        msm_dp_display->msm_dp_mode.out_fmt_is_yuv_420 ? false : 
>>>>> msm_dp_display->wide_bus_supported;
>>>>> -    msm_dp_display->catalog->wide_bus_en =
>>>>> -        msm_dp_display->msm_dp_mode.out_fmt_is_yuv_420 ? false : 
>>>>> msm_dp_display->wide_bus_supported;
>>>>> +    msm_dp_display->ctrl->wide_bus_en = msm_dp_panel- 
>>>>> >msm_dp_mode.out_fmt_is_yuv_420 ?
>>>>> +        false : msm_dp_display->wide_bus_supported;
>>>>> +    msm_dp_display->catalog->wide_bus_en = msm_dp_panel- 
>>>>> >msm_dp_mode.out_fmt_is_yuv_420 ?
>>>>> +        false : msm_dp_display->wide_bus_supported;
>>>>>    }
>>>>>    void msm_dp_bridge_hpd_enable(struct drm_bridge *bridge)
>>>>>
>>>>> -- 
>>>>> 2.34.1
>>>>>
>>>>
>>>
>>
> 


-- 
With best wishes
Dmitry