Re: [RFC PATCH 03/10] drm/mipi-dsi: add API for manual control over the DSI link power state
From: Neil Armstrong
Date: Mon Oct 23 2023 - 03:35:17 EST
On 16/10/2023 18:53, Dmitry Baryshkov wrote:
The MIPI DSI links do not fully fall into the DRM callbacks model. The
drm_bridge_funcs abstraction. Instead of having just two states (off and
on) the DSI hosts have separate LP-11 state. In this state the host is
on, but the video stream is not yet enabled.
Introduce API that allows DSI bridges / panels to control the DSI host
power up state.
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
drivers/gpu/drm/drm_mipi_dsi.c | 31 +++++++++++++++++++++++++++++++
include/drm/drm_mipi_dsi.h | 29 +++++++++++++++++++++++++----
2 files changed, 56 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index 14201f73aab1..c467162cb7d8 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -428,6 +428,37 @@ int devm_mipi_dsi_attach(struct device *dev,
}
EXPORT_SYMBOL_GPL(devm_mipi_dsi_attach);
+bool mipi_dsi_host_power_control_available(struct mipi_dsi_host *host)
+{
+ const struct mipi_dsi_host_ops *ops = host->ops;
+
+ return ops && ops->power_up;
+}
+EXPORT_SYMBOL_GPL(mipi_dsi_host_power_control_available);
+
+int mipi_dsi_host_power_up(struct mipi_dsi_host *host)
+{
+ const struct mipi_dsi_host_ops *ops = host->ops;
+
+ if (!mipi_dsi_host_power_control_available(host))
+ return -EOPNOTSUPP;
+
+ return ops->power_up ? ops->power_up(host) : 0;
+}
+EXPORT_SYMBOL_GPL(mipi_dsi_host_power_up);
+
+void mipi_dsi_host_power_down(struct mipi_dsi_host *host)
+{
+ const struct mipi_dsi_host_ops *ops = host->ops;
+
+ if (!mipi_dsi_host_power_control_available(host))
+ return;
+
+ if (ops->power_down)
+ ops->power_down(host);
+}
+EXPORT_SYMBOL_GPL(mipi_dsi_host_power_down);
+
static ssize_t mipi_dsi_device_transfer(struct mipi_dsi_device *dsi,
struct mipi_dsi_msg *msg)
{
diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 167742e579e3..e503c3e4d057 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -68,6 +68,8 @@ int mipi_dsi_create_packet(struct mipi_dsi_packet *packet,
* @attach: attach DSI device to DSI host
* @detach: detach DSI device from DSI host
* @transfer: transmit a DSI packet
+ * @power_up: enable DSI link and bring it to the LP-11 state
+ * @power_down: fully disable DSI link
*
* DSI packets transmitted by .transfer() are passed in as mipi_dsi_msg
* structures. This structure contains information about the type of packet
@@ -81,10 +83,18 @@ int mipi_dsi_create_packet(struct mipi_dsi_packet *packet,
* function will seldomly return anything other than the number of bytes
* contained in the transmit buffer on success.
*
- * Also note that those callbacks can be called no matter the state the
- * host is in. Drivers that need the underlying device to be powered to
- * perform these operations will first need to make sure it's been
- * properly enabled.
+ * Note: currently there are two modes of DSI power control. Legacy drivers
+ * will call those callbacks no matter the state the host is in. DSI host
+ * drivers that need the underlying device to be powered to perform these
+ * operations will first need to make sure it's been properly enabled.
+ *
+ * Newer drivers will set the @MIPI_DSI_MANUAL_POWERUP flag to indicate that
+ * they will call @mipi_dsi_power_up() and @mipi_dsi_power_down() to control
+ * the link state of the DSI host or they will set @MIPI_DSI_AUTO_POWERUP to
+ * indicate that the driver is fine with the link being powered up in DSI
+ * host's (atomic_)pre_enable() callback and then being disabled in the
+ * (atomic_)post_disable() callback. The transfer callback must only be called
+ * if the DSI host has been powered up and was not brought down.
*
* Note: some hosts (sunxi) can not send LP commands between HS video
* packets. Thus all DSI transfers sent in LP mode should be limited to the
@@ -97,6 +107,8 @@ struct mipi_dsi_host_ops {
struct mipi_dsi_device *dsi);
ssize_t (*transfer)(struct mipi_dsi_host *host,
const struct mipi_dsi_msg *msg);
+ int (*power_up)(struct mipi_dsi_host *host);
+ void (*power_down)(struct mipi_dsi_host *host);
};
/**
@@ -143,6 +155,10 @@ struct mipi_dsi_host *of_find_mipi_dsi_host_by_node(struct device_node *node);
#define MIPI_DSI_MODE_LPM BIT(11)
/* transmit data ending at the same time for all lanes within one hsync */
#define MIPI_DSI_HS_PKT_END_ALIGNED BIT(12)
+/* DSI peripheral driver manually controls DSI link powerup */
+#define MIPI_DSI_MANUAL_POWERUP BIT(13)
+/* DSI peripheral driver is fine with automatic DSI link power control */
+#define MIPI_DSI_AUTO_POWERUP BIT(14)
What happens if none of the bits are in the flags ?
Can't we implement "opportunistic power-up" on the first DSI command sent?
If a bridge/panel sends a DSI command, and if it happens before the DSI host enable, then
the DSI host will "pre-enable" the host and put the link in LP-11.
This would be simpler and would work whatever the pre_enable order.
But this won't work for the tc358767, except if we add a dummy DSI host command
which powers up the DSI link.
This won't fix the PS8640 either who also needs a disabled DSI link to initialize.
Neil
enum mipi_dsi_pixel_format {
MIPI_DSI_FMT_RGB888,
@@ -235,6 +251,11 @@ void mipi_dsi_device_unregister(struct mipi_dsi_device *dsi);
struct mipi_dsi_device *
devm_mipi_dsi_device_register_full(struct device *dev, struct mipi_dsi_host *host,
const struct mipi_dsi_device_info *info);
+
+bool mipi_dsi_host_power_control_available(struct mipi_dsi_host *host);
+int mipi_dsi_host_power_up(struct mipi_dsi_host *host);
+void mipi_dsi_host_power_down(struct mipi_dsi_host *host);
+
struct mipi_dsi_device *of_find_mipi_dsi_device_by_node(struct device_node *np);
int mipi_dsi_attach(struct mipi_dsi_device *dsi);
int mipi_dsi_detach(struct mipi_dsi_device *dsi);