Messages in this thread | | | Date | Thu, 2 Feb 2023 12:10:04 -0800 | Subject | Re: [RFT PATCH v2 2/3] drm/msm/dsi: Stop unconditionally powering up DSI hosts at modeset | From | Abhinav Kumar <> |
| |
On 2/1/2023 6:33 AM, Doug Anderson wrote: > Hi, > > On Tue, Jan 31, 2023 at 3:32 PM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: >> >> On 1/31/2023 2:18 PM, Douglas Anderson wrote: >>> In commit 7d8e9a90509f ("drm/msm/dsi: move DSI host powerup to modeset >>> time"), we moved powering up DSI hosts to modeset time. This wasn't >>> because it was an elegant design, but there were no better options. >>> >>> That commit actually ended up breaking ps8640, and thus was born >>> commit ec7981e6c614 ("drm/msm/dsi: don't powerup at modeset time for >>> parade-ps8640") as a temporary hack to un-break ps8640 by moving it to >>> the old way of doing things. It turns out that ps8640 _really_ doesn't >>> like its pre_enable() function to be called after >>> dsi_mgr_bridge_power_on(). Specifically (from experimentation, not >>> because I have any inside knowledge), it looks like the assertion of >>> "RST#" in the ps8640 runtime resume handler seems like it's not >>> allowed to happen after dsi_mgr_bridge_power_on() >>> >>> Recently, Dave Stevenson's series landed allowing bridges some control >>> over pre_enable ordering. The meaty commit for our purposes is commit >>> 4fb912e5e190 ("drm/bridge: Introduce pre_enable_prev_first to alter >>> bridge init order"). As documented by that series, if a bridge doesn't >>> set "pre_enable_prev_first" then we should use the old ordering. >>> >>> Now that we have the commit ("drm/bridge: tc358762: Set >>> pre_enable_prev_first") we can go back to the old ordering, which also >>> allows us to remove the ps8640 special case. >>> >>> One last note is that even without reverting commit 7d8e9a90509f >>> ("drm/msm/dsi: move DSI host powerup to modeset time"), if you _just_ >>> revert the ps8640 special case and try it out then it doesn't seem to >>> fail anymore. I spent time bisecting / debugging this and it turns out >>> to be mostly luck, so we still want this patch to make sure it's >>> solid. Specifically the reason it sorta works these days is because >>> we implemented wait_hpd_asserted() in ps8640 now, plus the magic of >>> "pm_runtime" autosuspend. The fact that we have wait_hpd_asserted() >>> implemented means that we actually power the bridge chip up just a wee >>> bit earlier and then the bridge happens to stay on because of >>> autosuspend and thus ends up powered before dsi_mgr_bridge_power_on(). >>> >>> Cc: Dave Stevenson <dave.stevenson@raspberrypi.com> >>> Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> >>> Cc: Abhinav Kumar <quic_abhinavk@quicinc.com> >>> Signed-off-by: Douglas Anderson <dianders@chromium.org> >>> --- >>> >>> Changes in v2: >>> - Don't fold dsi_mgr_bridge_power_on() back into dsi_mgr_bridge_pre_enable() >>> >>> drivers/gpu/drm/msm/dsi/dsi_manager.c | 38 +-------------------------- >>> 1 file changed, 1 insertion(+), 37 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c >>> index 1bbac72dad35..2197a54b9b96 100644 >>> --- a/drivers/gpu/drm/msm/dsi/dsi_manager.c >>> +++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c >>> @@ -34,32 +34,6 @@ static struct msm_dsi_manager msm_dsim_glb; >>> #define IS_SYNC_NEEDED() (msm_dsim_glb.is_sync_needed) >>> #define IS_MASTER_DSI_LINK(id) (msm_dsim_glb.master_dsi_link_id == id) >>> >>> -#ifdef CONFIG_OF >>> -static bool dsi_mgr_power_on_early(struct drm_bridge *bridge) >>> -{ >>> - struct drm_bridge *next_bridge = drm_bridge_get_next_bridge(bridge); >>> - >>> - /* >>> - * If the next bridge in the chain is the Parade ps8640 bridge chip >>> - * then don't power on early since it seems to violate the expectations >>> - * of the firmware that the bridge chip is running. >>> - * >>> - * NOTE: this is expected to be a temporary special case. It's expected >>> - * that we'll eventually have a framework that allows the next level >>> - * bridge to indicate whether it needs us to power on before it or >>> - * after it. When that framework is in place then we'll use it and >>> - * remove this special case. >>> - */ >>> - return !(next_bridge && next_bridge->of_node && >>> - of_device_is_compatible(next_bridge->of_node, "parade,ps8640")); >>> -} >>> -#else >>> -static inline bool dsi_mgr_power_on_early(struct drm_bridge *bridge) >>> -{ >>> - return true; >>> -} >>> -#endif >>> - >>> static inline struct msm_dsi *dsi_mgr_get_dsi(int id) >>> { >>> return msm_dsim_glb.dsi[id]; >>> @@ -265,12 +239,6 @@ static void dsi_mgr_bridge_power_on(struct drm_bridge *bridge) >>> int ret; >>> >>> DBG("id=%d", id); >>> - if (!msm_dsi_device_connected(msm_dsi)) >>> - return; >>> - >>> - /* Do nothing with the host if it is slave-DSI in case of bonded DSI */ >>> - if (is_bonded_dsi && !IS_MASTER_DSI_LINK(id)) >>> - return; >>> >> >> Why are these two checks removed? > > After this patch there is now one caller to this function and the one > caller does those exact same two checks immediately before calling > this function. Thus, they no longer do anything useful. > > -Doug
Ack, understood. dsi_mgr_bridge_pre_enable() has the same checks. Hence,
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
| |