Re: [PATCH 2/6] drm: rcar-du: lvds: Add reset control

Tomi Valkeinen <tomi.valkeinen+renesas@xxxxxxxxxxxxxxxx> · Thu, 19 Jan 2023 10:38:55 +0200

On 18/01/2023 23:06, Laurent Pinchart wrote:
Hi Tomi,

Thank you for the patch.

On Tue, Jan 17, 2023 at 03:51:50PM +0200, Tomi Valkeinen wrote:
From: Koji Matsuoka <koji.matsuoka.xm@xxxxxxxxxxx>

Reset LVDS using the reset control as CPG reset/release is required in
H/W manual sequence.

s@H/W@the hardware@

Signed-off-by: Koji Matsuoka <koji.matsuoka.xm@xxxxxxxxxxx>
Signed-off-by: LUU HOAI <hoai.luu.ub@xxxxxxxxxxx>
[tomi.valkeinen: Rewrite the patch description]
Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@xxxxxxxxxxxxxxxx>
---
  drivers/gpu/drm/rcar-du/Kconfig     |  1 +
  drivers/gpu/drm/rcar-du/rcar_lvds.c | 15 +++++++++++++++
  2 files changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/rcar-du/Kconfig b/drivers/gpu/drm/rcar-du/Kconfig
index a8f862c68b4f..151e400b996d 100644
--- a/drivers/gpu/drm/rcar-du/Kconfig
+++ b/drivers/gpu/drm/rcar-du/Kconfig
@@ -43,6 +43,7 @@ config DRM_RCAR_LVDS
  	select DRM_PANEL
  	select OF_FLATTREE
  	select OF_OVERLAY
+	select RESET_CONTROLLER
  
  config DRM_RCAR_USE_MIPI_DSI
  	bool "R-Car DU MIPI DSI Encoder Support"
diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
index 81a060c2fe3f..674b727cdaa2 100644
--- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
+++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
@@ -16,6 +16,7 @@
  #include <linux/of_device.h>
  #include <linux/of_graph.h>
  #include <linux/platform_device.h>
+#include <linux/reset.h>
  #include <linux/slab.h>
  #include <linux/sys_soc.h>
  
@@ -60,6 +61,7 @@ struct rcar_lvds_device_info {
  struct rcar_lvds {
  	struct device *dev;
  	const struct rcar_lvds_device_info *info;
+	struct reset_control *rstc;
  
  	struct drm_bridge bridge;
  
@@ -316,6 +318,8 @@ int rcar_lvds_pclk_enable(struct drm_bridge *bridge, unsigned long freq)
  
  	dev_dbg(lvds->dev, "enabling LVDS PLL, freq=%luHz\n", freq);
  
+	reset_control_deassert(lvds->rstc);

Can this fail ? Same in __rcar_lvds_atomic_enable().

Yes. Too hasty in picking a patch from the BSP =).

+
  	ret = clk_prepare_enable(lvds->clocks.mod);

It would be nice to switch this driver to runtime PM and move reset and
clock handling to the suspend/resume handlers. A candidate for a future
patch.

I have the runtime PM patch in my work branch, but on top. I'll pick 
that into this series, before adding the reset control. Makes error 
handling a bit simpler.

  	if (ret < 0)

Missing reset_control_assert(). Same in other error paths if applicable,
here and in __rcar_lvds_atomic_enable().

Yep.

 Tomi







