[PATCH v3 0/2] drm: introduce bus_flags for pixel clock polarity

[PATCH v3 0/2] drm: introduce bus_flags for pixel clock polarity

[Stefan Agner]

Hi,

Dropped the first patch in version 3 since that is already applied
in v4.6. Also moved all generic changes (including the changes in
panel-simple) to the first, generic patch.

Instead of using struct drm_display_mode to convey the pixel clock
polarity information, this patchset introduces a new field called
bus_flags stored in struct drm_display_info.

--
Stefan

Changes since v2:
- Rebased to v4.6 and dropped ("drm/fsl-dcu: use mode flags for hsync/vsync
  polarity"), already part of v4.6-rc1
- Moved all generic changes to the first commit

Changes since v1:
- Introduce bus_flags to convey the pixel clock polarity from
  panel-simple.c to the driver.

Stefan Agner (2):
  drm: introduce bus_flags in drm_display_info
  drm/fsl-dcu: use bus_flags for pixel clock polarity

 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c | 5 +++++
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h  | 4 ++--
 drivers/gpu/drm/panel/panel-simple.c       | 5 ++++-
 include/drm/drm_crtc.h                     | 9 +++++++++
 4 files changed, 20 insertions(+), 3 deletions(-)

-- 
2.7.4

[PATCH v3 1/2] drm: introduce bus_flags in drm_display_info

[Stefan Agner]

Introduce bus_flags to specify display bus properties like signal
polarities. This is useful for parallel display buses, e.g. to
specify the pixel clock or data enable polarity.

Suggested-by: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Manfred Schlaegl <manfred.schlaegl@gmx.at>
Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/gpu/drm/panel/panel-simple.c | 2 ++
 include/drm/drm_crtc.h               | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index ceb2048..77ae07f 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -72,6 +72,7 @@ struct panel_desc {
 	} delay;
 
 	u32 bus_format;
+	u32 bus_flags;
 };
 
 struct panel_simple {
@@ -144,6 +145,7 @@ static int panel_simple_get_fixed_modes(struct panel_simple *panel)
 	if (panel->desc->bus_format)
 		drm_display_info_set_bus_formats(&connector->display_info,
 						 &panel->desc->bus_format, 1);
+	connector->display_info.bus_flags = panel->desc->bus_flags;
 
 	return num;
 }
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index e0170bf..f8b37be 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -126,6 +126,14 @@ enum subpixel_order {
 #define DRM_COLOR_FORMAT_RGB444		(1<<0)
 #define DRM_COLOR_FORMAT_YCRCB444	(1<<1)
 #define DRM_COLOR_FORMAT_YCRCB422	(1<<2)
+
+#define DRM_BUS_FLAG_DE_LOW		(1<<0)
+#define DRM_BUS_FLAG_DE_HIGH		(1<<1)
+/* drive data on pos. edge */
+#define DRM_BUS_FLAG_PIXDATA_POSEDGE	(1<<2)
+/* drive data on neg. edge */
+#define DRM_BUS_FLAG_PIXDATA_NEGEDGE	(1<<3)
+
 /*
  * Describes a given display (e.g. CRT or flat panel) and its limitations.
  */
@@ -147,6 +155,7 @@ struct drm_display_info {
 
 	const u32 *bus_formats;
 	unsigned int num_bus_formats;
+	u32 bus_flags;
 
 	/* Mask of supported hdmi deep color modes */
 	u8 edid_hdmi_dc_modes;
-- 
2.7.4

[PATCH v3 2/2] drm/fsl-dcu: use bus_flags for pixel clock polarity

[Stefan Agner]

The drivers current default configuration drives the pixel data
on rising edge of the pixel clock. However, most display sample
data on rising edge... This leads to color shift artefacts visible
especially at edges.

This patch changes the relevant defines to be useful and actually
set the bits, and changes pixel clock polarity to drive the pixel
data on falling edge by default. The patch also adds an explicit
pixel clock polarity flag to the display introduced with the driver
(NEC WQVGA "nec,nl4827hc19-05b") using the new bus_flags field to
retain the initial behavior.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c | 5 +++++
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h  | 4 ++--
 drivers/gpu/drm/panel/panel-simple.c       | 3 ++-
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c
index 4ed7798..1ef437e 100644
--- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c
+++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c
@@ -66,6 +66,7 @@ static void fsl_dcu_drm_crtc_mode_set_nofb(struct drm_crtc *crtc)
 {
 	struct drm_device *dev = crtc->dev;
 	struct fsl_dcu_drm_device *fsl_dev = dev->dev_private;
+	struct drm_connector *con = &fsl_dev->connector.base;
 	struct drm_display_mode *mode = &crtc->state->mode;
 	unsigned int hbp, hfp, hsw, vbp, vfp, vsw, div, index, pol = 0;
 	unsigned long dcuclk;
@@ -82,6 +83,10 @@ static void fsl_dcu_drm_crtc_mode_set_nofb(struct drm_crtc *crtc)
 	vfp = mode->vsync_start - mode->vdisplay;
 	vsw = mode->vsync_end - mode->vsync_start;
 
+	/* INV_PXCK as default (most display sample data on rising edge) */
+	if (!(con->display_info.bus_flags & DRM_BUS_FLAG_PIXDATA_POSEDGE))
+		pol |= DCU_SYN_POL_INV_PXCK;
+
 	if (mode->flags & DRM_MODE_FLAG_NHSYNC)
 		pol |= DCU_SYN_POL_INV_HS_LOW;
 
diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h
index 6413ac9..af3a707 100644
--- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h
+++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h
@@ -47,8 +47,8 @@
 #define DCU_VSYN_PARA_FP(x)		(x)
 
 #define DCU_SYN_POL			0x0024
-#define DCU_SYN_POL_INV_PXCK_FALL	(0 << 6)
-#define DCU_SYN_POL_NEG_REMAIN		(0 << 5)
+#define DCU_SYN_POL_INV_PXCK		BIT(6)
+#define DCU_SYN_POL_NEG			BIT(5)
 #define DCU_SYN_POL_INV_VS_LOW		BIT(1)
 #define DCU_SYN_POL_INV_HS_LOW		BIT(0)
 
diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 77ae07f..b19c88f 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -1053,7 +1053,8 @@ static const struct panel_desc nec_nl4827hc19_05b = {
 		.width = 95,
 		.height = 54,
 	},
-	.bus_format = MEDIA_BUS_FMT_RGB888_1X24
+	.bus_format = MEDIA_BUS_FMT_RGB888_1X24,
+	.bus_flags = DRM_BUS_FLAG_PIXDATA_POSEDGE,
 };
 
 static const struct display_timing okaya_rs800480t_7x0gp_timing = {
-- 
2.7.4

Re: [PATCH v3 1/2] drm: introduce bus_flags in drm_display_info

[Daniel Vetter]

On Mon, Apr 18, 2016 at 01:38:14PM -0700, Stefan Agner wrote:
> Introduce bus_flags to specify display bus properties like signal
> polarities. This is useful for parallel display buses, e.g. to
> specify the pixel clock or data enable polarity.
> 
> Suggested-by: Thierry Reding <thierry.reding@gmail.com>
> Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
> Acked-by: Manfred Schlaegl <manfred.schlaegl@gmx.at>
> Signed-off-by: Stefan Agner <stefan@agner.ch>

Since I bikeshedded the old patches that used the display mode stuff to
death, and I think this makes a lot more sense:

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/panel/panel-simple.c | 2 ++
>  include/drm/drm_crtc.h               | 9 +++++++++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> index ceb2048..77ae07f 100644
> --- a/drivers/gpu/drm/panel/panel-simple.c
> +++ b/drivers/gpu/drm/panel/panel-simple.c
> @@ -72,6 +72,7 @@ struct panel_desc {
>  	} delay;
>  
>  	u32 bus_format;
> +	u32 bus_flags;
>  };
>  
>  struct panel_simple {
> @@ -144,6 +145,7 @@ static int panel_simple_get_fixed_modes(struct panel_simple *panel)
>  	if (panel->desc->bus_format)
>  		drm_display_info_set_bus_formats(&connector->display_info,
>  						 &panel->desc->bus_format, 1);
> +	connector->display_info.bus_flags = panel->desc->bus_flags;
>  
>  	return num;
>  }
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index e0170bf..f8b37be 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -126,6 +126,14 @@ enum subpixel_order {
>  #define DRM_COLOR_FORMAT_RGB444		(1<<0)
>  #define DRM_COLOR_FORMAT_YCRCB444	(1<<1)
>  #define DRM_COLOR_FORMAT_YCRCB422	(1<<2)
> +
> +#define DRM_BUS_FLAG_DE_LOW		(1<<0)
> +#define DRM_BUS_FLAG_DE_HIGH		(1<<1)
> +/* drive data on pos. edge */
> +#define DRM_BUS_FLAG_PIXDATA_POSEDGE	(1<<2)
> +/* drive data on neg. edge */
> +#define DRM_BUS_FLAG_PIXDATA_NEGEDGE	(1<<3)
> +
>  /*
>   * Describes a given display (e.g. CRT or flat panel) and its limitations.
>   */
> @@ -147,6 +155,7 @@ struct drm_display_info {
>  
>  	const u32 *bus_formats;
>  	unsigned int num_bus_formats;
> +	u32 bus_flags;
>  
>  	/* Mask of supported hdmi deep color modes */
>  	u8 edid_hdmi_dc_modes;
> -- 
> 2.7.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch