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Subject[PATCH v2 3/8] drm/bridge: simplify bridge timing info
Date
Bridges are typically connected to a parallel display signal with
pixel clock, sync signals and data lines. Parallel display signals
are also used in lower-end embedded display panels. For parallel
display panels we currently do not specify setup/hold times. From
discussions on the mailing list it seems not convincing that this
is currently really required for bridges either.

Remove setup/hold timings again to better align timing information
of displays and briges.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
drivers/gpu/drm/bridge/dumb-vga-dac.c | 17 +++++------------
include/drm/drm_bridge.h | 14 --------------
2 files changed, 5 insertions(+), 26 deletions(-)

diff --git a/drivers/gpu/drm/bridge/dumb-vga-dac.c b/drivers/gpu/drm/bridge/dumb-vga-dac.c
index d5aa0f931ef2..b2309ad228cf 100644
--- a/drivers/gpu/drm/bridge/dumb-vga-dac.c
+++ b/drivers/gpu/drm/bridge/dumb-vga-dac.c
@@ -229,14 +229,14 @@ static int dumb_vga_remove(struct platform_device *pdev)
/*
* We assume the ADV7123 DAC is the "default" for historical reasons
* Information taken from the ADV7123 datasheet, revision D.
- * NOTE: the ADV7123EP seems to have other timings and need a new timings
- * set if used.
*/
static const struct drm_bridge_timings default_dac_timings = {
- /* Timing specifications, datasheet page 7 */
+ /*
+ * From Timing diagram, datasheet page 7. The bridge samples
+ * on pixel clocks positive edge, hence the display controller
+ * should drive signals on the negative edge.
+ */
.input_bus_flags = DRM_BUS_FLAG_PIXDATA_NEGEDGE,
- .setup_time_ps = 500,
- .hold_time_ps = 1500,
};

/*
@@ -246,10 +246,6 @@ static const struct drm_bridge_timings default_dac_timings = {
static const struct drm_bridge_timings ti_ths8134_dac_timings = {
/* From timing diagram, datasheet page 9 */
.input_bus_flags = DRM_BUS_FLAG_PIXDATA_NEGEDGE,
- /* From datasheet, page 12 */
- .setup_time_ps = 3000,
- /* I guess this means latched input */
- .hold_time_ps = 0,
};

/*
@@ -259,9 +255,6 @@ static const struct drm_bridge_timings ti_ths8134_dac_timings = {
static const struct drm_bridge_timings ti_ths8135_dac_timings = {
/* From timing diagram, datasheet page 14 */
.input_bus_flags = DRM_BUS_FLAG_PIXDATA_NEGEDGE,
- /* From datasheet, page 16 */
- .setup_time_ps = 2000,
- .hold_time_ps = 500,
};

static const struct of_device_id dumb_vga_match[] = {
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 45e90f4b46c3..1a1d08350eaf 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -251,20 +251,6 @@ struct drm_bridge_timings {
* &drm_display_info->bus_flags.
*/
u32 input_bus_flags;
- /**
- * @setup_time_ps:
- *
- * Defines the time in picoseconds the input data lines must be
- * stable before the clock edge.
- */
- u32 setup_time_ps;
- /**
- * @hold_time_ps:
- *
- * Defines the time in picoseconds taken for the bridge to sample the
- * input signal after the clock edge.
- */
- u32 hold_time_ps;
};

/**
--
2.18.0
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