On Fri, Jul 31, 2026 at 07:19:14PM +0300, Cristian Ciocaltea wrote:
> Add the connector-level infrastructure to support HDMI 2.0 scrambling:
>
> - A drm_connector_hdmi_scrambler_supported() helper to report whether
> the source supports the scrambling capability, based on the presence
> of the newly introduced .scrambler_{enable|disable}() callbacks in
> drm_connector_hdmi_funcs are mandatory
> - A scrambler_needed flag to be managed by the hdmi state helpers based
> on the negotiated TMDS character rate and the source/sink scrambling
> capabilities
> - A scrambler_enabled flag to track whether scrambling is currently
> active
> - A delayed work item (scdc_work) to monitor sink-side scrambling status
> and retry the setup if the sink resets it
> - A scdc_work_initialized flag to support lazy initialization of the
> work item on the first scrambling enable and guard the teardown paths
>
> These are intended to be used by SCDC scrambling helpers to coordinate
> scrambling setup and teardown between the source driver and the DRM
> core.
>
> Tested-by: Maud Spierings <[email protected]>
> Tested-by: Diederik de Haas <[email protected]> # NanoPC-T6 LTS, Rock
> 5B
> Signed-off-by: Cristian Ciocaltea <[email protected]>
> ---
> drivers/gpu/drm/drm_connector.c | 31 ++++++++++++---
> include/drm/drm_connector.h | 83
> +++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 109 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 4721cdeafc84..a18410faf040 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -622,12 +622,29 @@ int drmm_connector_hdmi_init(struct drm_device *dev,
> * default with the actual controller capability. A value of zero keeps
> * the limit inferred from supported_hdmi_ver.
> */
> - if (hdmi_funcs->supported_hdmi_ver >= HDMI_VERSION_2_0)
> + if (hdmi_funcs->supported_hdmi_ver >= HDMI_VERSION_2_0) {
> + if (!hdmi_funcs->scrambler_enable ||
> !hdmi_funcs->scrambler_disable) {
> + drm_err(dev, "Scrambler callbacks missing for HDMI
> 2.x\n");
> + return -EINVAL;
> + }
> +
> connector->hdmi.max_tmds_char_rate =
> HDMI_2_0_TMDS_CHAR_RATE_MAX_HZ;
> - else if (hdmi_funcs->supported_hdmi_ver >= HDMI_VERSION_1_3)
> - connector->hdmi.max_tmds_char_rate =
> HDMI_1_3_TMDS_CHAR_RATE_MAX_HZ;
> - else if (hdmi_funcs->supported_hdmi_ver >= HDMI_VERSION_1_0)
> - connector->hdmi.max_tmds_char_rate =
> HDMI_1_0_TMDS_CHAR_RATE_MAX_HZ;
> + } else {
> + /*
> + * Scrambler callbacks are only valid for connectors advertising
> + * HDMI 2.0 capability. drm_connector_hdmi_scrambler_supported()
> + * relies on their presence to report scrambling support.
> + */
> + if (hdmi_funcs->scrambler_enable ||
> hdmi_funcs->scrambler_disable) {
> + drm_err(dev, "Scrambler callbacks unexpected for HDMI
> 1.x\n");
> + return -EINVAL;
> + }
> +
> + if (hdmi_funcs->supported_hdmi_ver >= HDMI_VERSION_1_3)
> + connector->hdmi.max_tmds_char_rate =
> HDMI_1_3_TMDS_CHAR_RATE_MAX_HZ;
> + else if (hdmi_funcs->supported_hdmi_ver >= HDMI_VERSION_1_0)
> + connector->hdmi.max_tmds_char_rate =
> HDMI_1_0_TMDS_CHAR_RATE_MAX_HZ;
> + }
I'd put it into a separate test (possibly earlier). Merging both the
tmds rate default and the scrambler callbacks check makes it messier
than it would be if we had two separate tests.
> if (hdmi_funcs->supported_tmds_char_rate) {
> if (hdmi_funcs->supported_tmds_char_rate >
> connector->hdmi.max_tmds_char_rate) {
> @@ -635,6 +652,7 @@ int drmm_connector_hdmi_init(struct drm_device *dev,
> connector->hdmi.max_tmds_char_rate);
> return -EINVAL;
> }
> +
> connector->hdmi.max_tmds_char_rate =
> hdmi_funcs->supported_tmds_char_rate;
> }
>
> @@ -918,6 +936,9 @@ void drm_connector_cleanup(struct drm_connector
> *connector)
> DRM_CONNECTOR_REGISTERED))
> drm_connector_unregister(connector);
>
> + if (connector->hdmi.scdc_work_initialized)
> + cancel_delayed_work_sync(&connector->hdmi.scdc_work);
> +
> platform_device_unregister(connector->hdmi_audio.codec_pdev);
>
> if (connector->privacy_screen) {
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index a6de3e63b462..89a140d6f064 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -28,6 +28,7 @@
> #include <linux/ctype.h>
> #include <linux/hdmi.h>
> #include <linux/notifier.h>
> +#include <linux/workqueue.h>
> #include <drm/drm_mode_object.h>
> #include <drm/drm_util.h>
> #include <drm/drm_property.h>
> @@ -1131,6 +1132,17 @@ struct drm_connector_hdmi_state {
> * @tmds_char_rate: TMDS Character Rate, in Hz.
> */
> unsigned long long tmds_char_rate;
> +
> + /**
> + * @scrambler_needed: Whether HDMI 2.0 SCDC scrambling is required
> + * for the negotiated mode/bpc/format.
> + *
> + * Computed by drm_atomic_helper_connector_hdmi_check() according to
> + * the HDMI 2.0 specification: scrambling is mandatory above a 340 MHz
> + * TMDS character rate. Optional scrambling at lower rates is
> + * deliberately not requested by the helper.
> + */
> + bool scrambler_needed;
> };
>
> /**
> @@ -1481,6 +1493,36 @@ struct drm_connector_hdmi_funcs {
> */
> const struct drm_edid *(*read_edid)(struct drm_connector *connector);
>
> + /**
> + * @scrambler_enable:
> + *
> + * The callback is invoked via @drm_connector_hdmi_enable_scrambling
> + * during commit to setup SCDC scrambling and high TMDS clock ratio on
> + * the source side.
> + *
> + * The @scrambler_enable callback is mandatory if HDMI 2.0 is to be
> + * supported.
> + *
> + * Returns:
> + * 0 on success, a negative error code otherwise
> + */
> + int (*scrambler_enable)(struct drm_connector *connector);
> +
> + /**
> + * @scrambler_disable:
> + *
> + * The callback is invoked via @drm_connector_hdmi_disable_scrambling
> + * during commit to tear down SCDC scrambling and high TMDS clock ratio
> + * on the source side.
> + *
> + * The @scrambler_disable callback is mandatory if HDMI 2.0 is to be
> + * supported.
> + *
> + * Returns:
> + * 0 on success, a negative error code otherwise
> + */
> + int (*scrambler_disable)(struct drm_connector *connector);
> +
> /**
> * @avi:
> *
> @@ -2111,6 +2153,25 @@ struct drm_connector_hdmi {
> */
> unsigned long long max_tmds_char_rate;
>
> + /**
> + * @scrambler_enabled: Tracks whether HDMI 2.0 scrambler is currently
> enabled.
> + */
> + bool scrambler_enabled;
> +
> + /**
> + * @scdc_work: Work item currently used to monitor sink-side scrambling
> + * status and retry setup if the sink resets it.
> + */
> + struct delayed_work scdc_work;
> +
> + /**
> + * @scdc_work_initialized: Tracks whether @scdc_work has been set up via
> + * INIT_DELAYED_WORK(). The work item is initialized lazily on the first
> + * scrambling enable, so this guards the teardown paths against touching
> + * an uninitialized work item.
> + */
> + bool scdc_work_initialized;
> +
Why should we track whether it's initialized or not? I'd always
initialize it, but only ever schedule something if we're using the
scrambler.
Maxime
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