Re: [PATCH v10 15/24] drm/mediatek: Remove ineffectual power management codes

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Il 19/10/23 07:56, Hsiao Chien Sung ha scritto:
Display modules will be powered on when .atomic_enable(),
there is no need to do it again in mtk_crtc_ddp_hw_init().
Besides, the DRM devices are created manually when mtk-mmsys
is probed and there is no power domain linked to it.

Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")

Signed-off-by: Hsiao Chien Sung <shawn.sung@xxxxxxxxxxxx>
---
  drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 18 +++---------------
  1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
index bc4cc75cca18..c7edd80be428 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
@@ -6,7 +6,6 @@
  #include <linux/clk.h>
  #include <linux/dma-mapping.h>
  #include <linux/mailbox_controller.h>
-#include <linux/pm_runtime.h>
  #include <linux/soc/mediatek/mtk-cmdq.h>
  #include <linux/soc/mediatek/mtk-mmsys.h>
  #include <linux/soc/mediatek/mtk-mutex.h>
@@ -362,22 +361,16 @@ static int mtk_crtc_ddp_hw_init(struct mtk_drm_crtc *mtk_crtc, struct drm_atomic
  		drm_connector_list_iter_end(&conn_iter);
  	}
- ret = pm_runtime_resume_and_get(crtc->dev->dev);
-	if (ret < 0) {
-		DRM_ERROR("Failed to enable power domain: %d\n", ret);
-		return ret;
-	}
-

Are you really sure that writes to DISP_REG_OVL_xxx and others in other modules,
called by the .layer_config() callback, can be successfully done on an unpowered
and/or unclocked module, on all MediaTek SoCs?
This looks a bit odd.

  	ret = mtk_mutex_prepare(mtk_crtc->mutex);
  	if (ret < 0) {
  		DRM_ERROR("Failed to enable mutex clock: %d\n", ret);
-		goto err_pm_runtime_put;
+		goto error;
  	}
ret = mtk_crtc_ddp_clk_enable(mtk_crtc);
  	if (ret < 0) {
  		DRM_ERROR("Failed to enable component clocks: %d\n", ret);
-		goto err_mutex_unprepare;
+		goto error;
  	}
for (i = 0; i < mtk_crtc->ddp_comp_nr - 1; i++) {
@@ -426,16 +419,13 @@ static int mtk_crtc_ddp_hw_init(struct mtk_drm_crtc *mtk_crtc, struct drm_atomic

...because you could otherwise just call pm_runtime_put() here, instead of removing
the pm_runtime_resume_and_get() call, which is something I would advise to do.

Regards,
Angelo

  	return 0;
-err_mutex_unprepare:
+error:
  	mtk_mutex_unprepare(mtk_crtc->mutex);
-err_pm_runtime_put:
-	pm_runtime_put(crtc->dev->dev);
  	return ret;
  }
static void mtk_crtc_ddp_hw_fini(struct mtk_drm_crtc *mtk_crtc)
  {
-	struct drm_device *drm = mtk_crtc->base.dev;
  	struct drm_crtc *crtc = &mtk_crtc->base;
  	int i;
@@ -465,8 +455,6 @@ static void mtk_crtc_ddp_hw_fini(struct mtk_drm_crtc *mtk_crtc)
  	mtk_crtc_ddp_clk_disable(mtk_crtc);
  	mtk_mutex_unprepare(mtk_crtc->mutex);
- pm_runtime_put(drm->dev);
-
  	if (crtc->state->event && !crtc->state->active) {
  		spin_lock_irq(&crtc->dev->event_lock);
  		drm_crtc_send_vblank_event(crtc, crtc->state->event);






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