Add helpers to manage the full lifecycle of HDMI 2.0 SCDC scrambling on both source and sink sides:
- drm_scdc_start_scrambling(): configures SCDC scrambling and high TMDS clock ratio and starts a periodic work item that monitors the sink's SCDC scrambling status, retrying setup when the sink loses state - drm_scdc_stop_scrambling(): tears down scrambling on both sides and cancels the monitoring work - drm_scdc_sync_status(): triggers a CRTC reset on reconnection to restore SCDC state lost during sink disconnects within an active display pipeline Signed-off-by: Cristian Ciocaltea <[email protected]> --- drivers/gpu/drm/display/drm_scdc_helper.c | 245 +++++++++++++++++++++++++++++- include/drm/display/drm_scdc_helper.h | 6 +- 2 files changed, 244 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/display/drm_scdc_helper.c b/drivers/gpu/drm/display/drm_scdc_helper.c index cb6632346aad..f71728e5ca81 100644 --- a/drivers/gpu/drm/display/drm_scdc_helper.c +++ b/drivers/gpu/drm/display/drm_scdc_helper.c @@ -21,15 +21,22 @@ * DEALINGS IN THE SOFTWARE. */ +#include <linux/delay.h> #include <linux/export.h> #include <linux/i2c.h> +#include <linux/minmax.h> #include <linux/slab.h> -#include <linux/delay.h> + +#include <drm/drm_atomic.h> +#include <drm/drm_atomic_helper.h> +#include <drm/drm_bridge_helper.h> +#include <drm/drm_connector.h> +#include <drm/drm_crtc.h> +#include <drm/drm_device.h> +#include <drm/drm_modeset_lock.h> +#include <drm/drm_print.h> #include <drm/display/drm_scdc_helper.h> -#include <drm/drm_connector.h> -#include <drm/drm_device.h> -#include <drm/drm_print.h> /** * DOC: scdc helpers @@ -50,10 +57,14 @@ * has to track the connector status changes using interrupts and * restore the SCDC status. The typical solution for this is to trigger an * empty modeset in drm_connector_helper_funcs.detect_ctx(), like what vc4 does - * in vc4_hdmi_reset_link(). + * in vc4_hdmi_reset_link(). Alternatively, use the HDMI connector framework + * which ensures drm_scdc_sync_status() is called in the context of + * drm_atomic_helper_connector_hdmi_hotplug_ctx(). */ -#define SCDC_I2C_SLAVE_ADDRESS 0x54 +#define SCDC_I2C_SLAVE_ADDRESS 0x54 +#define SCDC_MAX_SOURCE_VERSION 0x1 +#define SCDC_STATUS_POLL_DELAY_MS 1000 #define drm_scdc_dbg(connector, fmt, ...) \ drm_dbg_kms((connector)->dev, "[CONNECTOR:%d:%s] " fmt, \ @@ -270,3 +281,225 @@ bool drm_scdc_set_high_tmds_clock_ratio(struct drm_connector *connector, return true; } EXPORT_SYMBOL(drm_scdc_set_high_tmds_clock_ratio); + +static int drm_scdc_try_scrambling_setup(struct drm_connector *connector) +{ + bool done; + + done = drm_scdc_set_high_tmds_clock_ratio(connector, true); + if (!done) + return -EIO; + + done = drm_scdc_set_scrambling(connector, true); + if (!done) + return -EIO; + + if (READ_ONCE(connector->hdmi.scrambler_enabled)) + schedule_delayed_work(&connector->hdmi.scdc_work, + msecs_to_jiffies(SCDC_STATUS_POLL_DELAY_MS)); + + return 0; +} + +static void drm_scdc_monitor_scrambler(struct drm_connector *connector) +{ + if (READ_ONCE(connector->hdmi.scrambler_enabled) && + !drm_scdc_get_scrambling_status(connector)) + drm_scdc_try_scrambling_setup(connector); +} + +static int drm_scdc_reset_crtc(struct drm_connector *connector, + struct drm_modeset_acquire_ctx *ctx) +{ + struct drm_device *dev = connector->dev; + struct drm_crtc *crtc; + u8 config; + int ret; + + if (!ctx) + return 0; + + /* + * This is normally part of .detect_ctx() call path, which already holds + * connection_mutex through @ctx. However, re-acquiring it with the + * same context is a no-op and makes the helper safe under any caller. + */ + ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx); + if (ret) + return ret; + + if (!connector->state) + return 0; + + crtc = connector->state->crtc; + if (!crtc) + return 0; + + ret = drm_scdc_readb(connector->ddc, SCDC_TMDS_CONFIG, &config); + if (ret) { + drm_scdc_dbg(connector, "Failed to read TMDS config: %d\n", ret); + return ret; + } + + if ((config & SCDC_SCRAMBLING_ENABLE) && + (config & SCDC_TMDS_BIT_CLOCK_RATIO_BY_40)) + return 0; + + /* + * Reset the CRTC to suspend TMDS transmission, conforming to HDMI 2.0 + * spec which requires scrambled data not to be sent before the sink is + * configured, and TMDS clock to be suspended while changing the clock + * ratio. The disable/re-enable cycle triggered by the reset should + * call drm_scdc_start_scrambling() during re-enable, properly + * configuring the sink before data transmission resumes. + */ + + drm_scdc_dbg(connector, "Resetting CRTC to restore SCDC status\n"); + + ret = drm_atomic_helper_reset_crtc(crtc, ctx); + if (ret && ret != -EDEADLK) + drm_scdc_dbg(connector, "Failed to reset CRTC: %d\n", ret); + + return ret; +} + +/** + * drm_scdc_start_scrambling - activate scrambling and monitor SCDC status + * @connector: connector + * + * Enables scrambling and high TMDS clock ratio on both source and sink sides. + * Additionally, use a delayed work item to monitor the scrambling status on + * the sink side and retry the operation, as some displays refuse to set the + * scrambling bit right away. + * + * Returns: + * Zero if scrambling is set successfully, an error code otherwise. + */ +int drm_scdc_start_scrambling(struct drm_connector *connector) +{ + struct drm_display_info *info = &connector->display_info; + struct drm_connector_hdmi *hdmi = &connector->hdmi; + int ret; + u8 ver; + + if (!hdmi->scrambler_supported) { + drm_scdc_dbg(connector, "Scrambler not supported, bailing.\n"); + return -EINVAL; + } + + if (!info->is_hdmi || + !info->hdmi.scdc.supported || + !info->hdmi.scdc.scrambling.supported) { + drm_scdc_dbg(connector, "Sink doesn't support scrambling.\n"); + return -EINVAL; + } + + drm_scdc_dbg(connector, "Enabling scrambling\n"); + + ret = drm_scdc_readb(connector->ddc, SCDC_SINK_VERSION, &ver); + if (ret) { + drm_scdc_dbg(connector, "Failed to read SCDC_SINK_VERSION: %d\n", ret); + return ret; + } + + ret = drm_scdc_writeb(connector->ddc, SCDC_SOURCE_VERSION, + min_t(u8, ver, SCDC_MAX_SOURCE_VERSION)); + if (ret) { + drm_scdc_dbg(connector, "Failed to write SCDC_SOURCE_VERSION: %d\n", ret); + return ret; + } + + hdmi->scdc_cb = drm_scdc_monitor_scrambler; + WRITE_ONCE(hdmi->scrambler_enabled, true); + + ret = drm_scdc_try_scrambling_setup(connector); + if (!ret) + ret = hdmi->funcs->scrambler_enable(connector); + + if (ret) { + WRITE_ONCE(hdmi->scrambler_enabled, false); + cancel_delayed_work_sync(&hdmi->scdc_work); + hdmi->scdc_cb = NULL; + + drm_scdc_set_scrambling(connector, false); + drm_scdc_set_high_tmds_clock_ratio(connector, false); + } + + return ret; +} +EXPORT_SYMBOL(drm_scdc_start_scrambling); + +/** + * drm_scdc_stop_scrambling - deactivate scrambling and SCDC status monitor + * @connector: connector + * + * Disables scrambling and high TMDS clock ratio on both source and sink sides. + * Also cancels the SCDC status monitoring work item, if it is still pending. + * + * Returns: + * Zero if scrambling is reset successfully, an error code otherwise. + */ +int drm_scdc_stop_scrambling(struct drm_connector *connector) +{ + struct drm_display_info *info = &connector->display_info; + struct drm_connector_hdmi *hdmi = &connector->hdmi; + + if (!hdmi->scrambler_supported) { + drm_scdc_dbg(connector, "Scrambler not supported, bailing.\n"); + return -EINVAL; + } + + if (!READ_ONCE(hdmi->scrambler_enabled)) + return 0; + + drm_scdc_dbg(connector, "Disabling scrambling\n"); + + WRITE_ONCE(hdmi->scrambler_enabled, false); + cancel_delayed_work_sync(&hdmi->scdc_work); + hdmi->scdc_cb = NULL; + + if (connector->status == connector_status_connected && + info->is_hdmi && info->hdmi.scdc.supported && + info->hdmi.scdc.scrambling.supported) { + drm_scdc_set_scrambling(connector, false); + drm_scdc_set_high_tmds_clock_ratio(connector, false); + } + + return hdmi->funcs->scrambler_disable(connector); +} +EXPORT_SYMBOL(drm_scdc_stop_scrambling); + +/** + * drm_scdc_sync_status - resync the sink-side SCDC upon reconnect + * @connector: connector + * @plugged: connector plugged status event + * @ctx: initialized lock acquisition context + * + * When receiving hotplug disconnect/reconnect event, while the display is + * still active (CRTC enabled), the SCDC status on the sink side is reset + * and must be explicitly restored. + * + * The typical solution for this is to trigger an empty modeset in + * drm_connector_helper_funcs.detect_ctx(), which is what this helper does + * by triggering a CRTC reset on reconnection. + * + * When making use of the HDMI connector framework, this is automatically + * triggered via drm_atomic_helper_connector_hdmi_hotplug_ctx(). + * + * Returns: + * Zero on success, an error code otherwise, including -EDEADLK. + */ +int drm_scdc_sync_status(struct drm_connector *connector, bool plugged, + struct drm_modeset_acquire_ctx *ctx) +{ + struct drm_connector_hdmi *hdmi = &connector->hdmi; + + if (hdmi->scrambler_supported && plugged && + READ_ONCE(hdmi->scrambler_enabled)) + return drm_scdc_reset_crtc(connector, ctx); + + /* TODO: Also handle HDMI 2.1 FRL link training */ + + return 0; +} +EXPORT_SYMBOL(drm_scdc_sync_status); diff --git a/include/drm/display/drm_scdc_helper.h b/include/drm/display/drm_scdc_helper.h index 34600476a1b9..5d9a37bbb362 100644 --- a/include/drm/display/drm_scdc_helper.h +++ b/include/drm/display/drm_scdc_helper.h @@ -29,6 +29,7 @@ #include <drm/display/drm_scdc.h> struct drm_connector; +struct drm_modeset_acquire_ctx; struct i2c_adapter; ssize_t drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer, @@ -76,5 +77,8 @@ bool drm_scdc_get_scrambling_status(struct drm_connector *connector); bool drm_scdc_set_scrambling(struct drm_connector *connector, bool enable); bool drm_scdc_set_high_tmds_clock_ratio(struct drm_connector *connector, bool set); - +int drm_scdc_start_scrambling(struct drm_connector *connector); +int drm_scdc_stop_scrambling(struct drm_connector *connector); +int drm_scdc_sync_status(struct drm_connector *connector, bool plugged, + struct drm_modeset_acquire_ctx *ctx); #endif -- 2.54.0
