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SubjectRe: [PATCH v4] drm/msm/dsi: don't powerup at modeset time for parade-ps8640
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On 13/05/2022 01:00, Douglas Anderson wrote:
> Commit 7d8e9a90509f ("drm/msm/dsi: move DSI host powerup to modeset
> time") caused sc7180 Chromebooks that use the parade-ps8640 bridge
> chip to fail to turn the display back on after it turns off.
>
> Unfortunately, it doesn't look easy to fix the parade-ps8640 driver to
> handle the new power sequence. The Linux driver has almost nothing in
> it and most of the logic for this bridge chip is in black-box firmware
> that the bridge chip uses.
>
> Also unfortunately, reverting the patch will break "tc358762".
>
> The long term solution here is probably Dave Stevenson's series [1]
> that would give more flexibility. However, that is likely not a quick
> fix.
>
> For the short term, we'll look at the compatible of the next bridge in
> the chain and go back to the old way for the Parade PS8640 bridge
> chip. If it's found that other bridge chips also need this workaround
> then we can add them to the list or consider inverting the condition.
>
> [1] https://lore.kernel.org/r/cover.1646406653.git.dave.stevenson@raspberrypi.com
>
> Fixes: 7d8e9a90509f ("drm/msm/dsi: move DSI host powerup to modeset time")
> Suggested-by: Rob Clark <robdclark@gmail.com>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

> ---
> Note that, unlike `struct device`, `struct drm_bridge` still has a
> `#ifdef` around the `of_node`. The extra stub function in this patch
> is to make sure that we can pass COMPILE_TEST, not because I expect
> that we'll actually run into real users who are running this driver
> without device tree.
>
> Changes in v4:
> - Use the compatible string of the next bridge as per Rob.
>
> Changes in v3:
> - No longer a revert; now a module parameter.
>
> Changes in v2:
> - Remove the mud from my face.
>
> drivers/gpu/drm/msm/dsi/dsi_manager.c | 26 +++++++++++++++++++++++++-
> 1 file changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> index 50b987658b1f..2cabba65a8f1 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> @@ -34,6 +34,26 @@ 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.
> + */
> + 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];
> @@ -389,6 +409,9 @@ static void dsi_mgr_bridge_pre_enable(struct drm_bridge *bridge)
> if (is_bonded_dsi && !IS_MASTER_DSI_LINK(id))
> return;
>
> + if (!dsi_mgr_power_on_early(bridge))
> + dsi_mgr_bridge_power_on(bridge);
> +
> /* Always call panel functions once, because even for dual panels,
> * there is only one drm_panel instance.
> */
> @@ -570,7 +593,8 @@ static void dsi_mgr_bridge_mode_set(struct drm_bridge *bridge,
> if (is_bonded_dsi && other_dsi)
> msm_dsi_host_set_display_mode(other_dsi->host, adjusted_mode);
>
> - dsi_mgr_bridge_power_on(bridge);
> + if (dsi_mgr_power_on_early(bridge))
> + dsi_mgr_bridge_power_on(bridge);
> }
>
> static enum drm_mode_status dsi_mgr_bridge_mode_valid(struct drm_bridge *bridge,


--
With best wishes
Dmitry

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