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

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Il 19/10/23 11:52, Shawn Sung (宋孝謙) ha scritto:
Hi Angelo,

On Thu, 2023-10-19 at 11:07 +0200, AngeloGioacchino Del Regno wrote:
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.

Not sure if I get your point correctly. We removed this PM API because:

1. mtk_crtc_ddp_hw_init() is called by mtk_drm_crtc_atomic_enable(),
and the new inline function mtk_ddp_comp_power_on() is called before hw
init, we can make sure the power is on before configuring the hardware.

2. The device "crtc->dev->dev" here is assigned by the probe function
of mtk-mmsys, which will be look like "mediatek-drm.auto.13", and this
device is not linked to any power domain.


Thanks for the clarification. In this case:

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>


   	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


Thanks,
Shawn






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