drm/mcde: Fix display data flow control

Revamp the way that the flow of data to the display is
defined.

I realized that the hardware supports something like
5 different modes of flow: oneshot, command with TE IRQ,
command with BTA (bus turn around) and TE IRQ, video
with TE IRQ and video without TE IRQ instead synchronizing
to the output of the MCDE DSI formatter.

Like before the selection of the type of flow is done
from the DSI driver when we attach it to the MCDE and we
get to know what the display wants.

The new video mode synchronization method from the MCDE DSI
formatter is used on some upstream devices such as Golden.
This is the new default for video mode: stateless panels
do not as a rule generate TE IRQs.

Another semantic change is that we stop sending
a TE request before every command when sending data to
a display in command mode: this should only be explicitly
requested when using BTA, according to the vendor driver.

This has been tested and works fine with the command mode
displays I have. (All that are supported upstream.)

Reported-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Stephan Gerhold <stephan@gerhold.net>
Cc: Stephan Gerhold <stephan@gerhold.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200729090915.252730-2-linus.walleij@linaro.org

1 files changed, 23 insertions, 3 deletions

diff --git a/drivers/gpu/drm/mcde/mcde_drm.h b/drivers/gpu/drm/mcde/mcde_drm.h
index 679c2c4e6d9d..3e406d783465 100644
--- a/drivers/gpu/drm/mcde/mcde_drm.h
+++ b/drivers/gpu/drm/mcde/mcde_drm.h
@@ -9,6 +9,22 @@
 #ifndef _MCDE_DRM_H_
 #define _MCDE_DRM_H_
 
+enum mcde_flow_mode {
+	/* One-shot mode: flow stops after one frame */
+	MCDE_COMMAND_ONESHOT_FLOW,
+	/* Command mode with tearing effect (TE) IRQ sync */
+	MCDE_COMMAND_TE_FLOW,
+	/*
+	 * Command mode with bus turn-around (BTA) and tearing effect
+	 * (TE) IRQ sync.
+	 */
+	MCDE_COMMAND_BTA_TE_FLOW,
+	/* Video mode with tearing effect (TE) sync IRQ */
+	MCDE_VIDEO_TE_FLOW,
+	/* Video mode with the formatter itself as sync source */
+	MCDE_VIDEO_FORMATTER_FLOW,
+};
+
 struct mcde {
 	struct drm_device drm;
 	struct device *dev;
@@ -18,9 +34,7 @@ struct mcde {
 	struct drm_simple_display_pipe pipe;
 	struct mipi_dsi_device *mdsi;
 	s16 stride;
-	bool te_sync;
-	bool video_mode;
-	bool oneshot_mode;
+	enum mcde_flow_mode flow_mode;
 	unsigned int flow_active;
 	spinlock_t flow_lock; /* Locks the channel flow control */
 
@@ -36,6 +50,12 @@ struct mcde {
 
 #define to_mcde(dev) container_of(dev, struct mcde, drm)
 
+static inline bool mcde_flow_is_video(struct mcde *mcde)
+{
+	return (mcde->flow_mode == MCDE_VIDEO_TE_FLOW ||
+		mcde->flow_mode == MCDE_VIDEO_FORMATTER_FLOW);
+}
+
 bool mcde_dsi_irq(struct mipi_dsi_device *mdsi);
 void mcde_dsi_te_request(struct mipi_dsi_device *mdsi);
 extern struct platform_driver mcde_dsi_driver;