[PATCH v4 4/6] drm: scrambling support in drm layer

Shashank Sharma
2017-02-22T13:18:29Z

HDMI 2.0 spec mandates scrambling for modes with pixel clock higher
than 340 MHz. This patch adds few new functions in drm layer for
core drivers to enable/disable scrambling.

This patch adds:
- A function to detect scrambling support parsing HF-VSDB
- A function to check scrambling status runtime using SCDC read.
- Two functions to enable/disable scrambling using SCDC read/write.
- Few new bools to reflect scrambling support and status.

V2: Addressed review comments from Thierry, Ville and Dhinakaran
Thierry:
- Mhz -> MHz in comments and commit message.
- i2c -> I2C in comments.
- Fix the function documentations, keep in sync with drm_scdc_helper.c
- drm_connector -> DRM connector.
- Create structure for SCDC, and save scrambling status inside that,
in a sub-structure.
- Call this sub-structure scrambling instead of scr_info.
- low_rates -> low_clocks in scrambling status structure.
- Store the return value of I2C read/write and print the error code
in case of failure.

Thierry and Ville:
- Move the scrambling enable/disable/query functions in
drm_scdc_helper.c file.
- Add drm_SCDC prefix for the functions.
- Optimize the return statement from function
drm_SCDC_check_scrambling_status.

Ville:
- Dont overwrite saved max TMDS clock value in display_info,
if max tmds clock from HF-VSDB is not > 340 MHz.
- drm_detect_hdmi_scrambling -> drm_parse_hdmi_forum_vsdb.
- Remove dynamic tracking of SCDC status from DRM layer, force bool.
- Program clock ratio bit also, while enabling scrambling.

Dhinakaran:
- Add a comment about *5000 while extracting max clock supported.

V3: Addressed review comments from Jose.
- Create separate functions to enable scrambling and to set TMDS
clock/character rate ratio.

V4: Rebase

Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
---
drivers/gpu/drm/drm_edid.c | 33 +++++++-
drivers/gpu/drm/drm_scdc_helper.c | 164 ++++++++++++++++++++++++++++++++++++++
include/drm/drm_connector.h | 19 +++++
include/drm/drm_edid.h | 6 +-
include/drm/drm_scdc_helper.h | 41 ++++++++++
5 files changed, 261 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 63b79be..1e18c0a 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -37,6 +37,7 @@
#include <drm/drm_edid.h>
#include <drm/drm_encoder.h>
#include <drm/drm_displayid.h>
+#include <drm/drm_scdc_helper.h>

#include "drm_crtc_internal.h"

@@ -3811,13 +3812,43 @@ enum hdmi_quantization_range
static void drm_parse_hdmi_forum_vsdb(struct drm_connector *connector,
const u8 *hf_vsdb)
{
- struct drm_hdmi_info *hdmi = &connector->display_info.hdmi;
+ struct drm_display_info *display = &connector->display_info;
+ struct drm_hdmi_info *hdmi = &display->hdmi;

if (hf_vsdb[6] & 0x80) {
hdmi->scdc.supported = true;
if (hf_vsdb[6] & 0x40)
hdmi->scdc.read_request = true;
}
+
+ /*
+ * All HDMI 2.0 monitors must support scrambling at rates > 340 MHz.
+ * And as per the spec, three factors confirm this:
+ * * Availability of a HF-VSDB block in EDID (check)
+ * * Non zero Max_TMDS_Char_Rate filed in HF-VSDB (let's check)
+ * * SCDC support available (let's check)
+ * Lets check it out.
+ */
+
+ if (hf_vsdb[5]) {
+ /* max clock is 5000 KHz times block value */
+ u32 max_tmds_clock = hf_vsdb[5] * 5000;
+ struct drm_scdc *scdc = &hdmi->scdc;
+
+ if (max_tmds_clock > 340000) {
+ display->max_tmds_clock = max_tmds_clock;
+ DRM_DEBUG_KMS("HF-VSDB: max TMDS clock %d kHz\n",
+ display->max_tmds_clock);
+ }
+
+ if (scdc->supported) {
+ scdc->scrambling.supported = true;
+
+ /* Few sinks support scrambling for cloks < 340M */
+ if ((hf_vsdb[6] & 0x8))
+ scdc->scrambling.low_rates = true;
+ }
+ }
}

static void drm_parse_hdmi_deep_color_info(struct drm_connector *connector,
diff --git a/drivers/gpu/drm/drm_scdc_helper.c b/drivers/gpu/drm/drm_scdc_helper.c
index fe0e121..c0cf82b 100644
--- a/drivers/gpu/drm/drm_scdc_helper.c
+++ b/drivers/gpu/drm/drm_scdc_helper.c
@@ -22,8 +22,10 @@
*/

#include <linux/slab.h>
+#include <linux/delay.h>

#include <drm/drm_scdc_helper.h>
+#include <drm/drmP.h>

/**
* DOC: scdc helpers
@@ -109,3 +111,165 @@ ssize_t drm_scdc_write(struct i2c_adapter *adapter, u8 offset,
return err;
}
EXPORT_SYMBOL(drm_scdc_write);
+
+/**
+ * drm_scdc_check_scrambling_status - what is status of scrambling?
+ * @adapter: I2C adapter for DDC channel
+ *
+ * Reads the scrambler status over SCDC, and checks the
+ * scrambling status.
+ *
+ * Returns:
+ * True if the scrambling is enabled, false otherwise.
+ */
+
+bool drm_scdc_check_scrambling_status(struct i2c_adapter *adapter)
+{
+ u8 status;
+ int ret;
+
+ ret = drm_scdc_readb(adapter, SCDC_SCRAMBLER_STATUS, &status);
+ if (ret < 0) {
+ DRM_ERROR("Failed to read scrambling status, error %d\n", ret);
+ return false;
+ }
+
+ return status & SCDC_SCRAMBLING_STATUS;
+}
+EXPORT_SYMBOL(drm_scdc_check_scrambling_status);
+
+/**
+ * drm_scdc_enable_scrambling - enable scrambling
+ * @adapter: I2C adapter for DDC channel
+ *
+ * Writes the TMDS config over SCDC channel, and enables scrambling
+ * Returns:
+ * True if scrambling is successfully enabled, false otherwise.
+ */
+
+bool drm_scdc_enable_scrambling(struct i2c_adapter *adapter)
+{
+ u8 config;
+ int ret;
+
+ ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
+ if (ret < 0) {
+ DRM_ERROR("Failed to read tmds config, err=%d\n", ret);
+ return false;
+ }
+
+ config |= SCDC_SCRAMBLING_ENABLE;
+
+ ret = drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config);
+ if (ret < 0) {
+ DRM_ERROR("Failed to enable scrambling, error %d\n", ret);
+ return false;
+ }
+
+ return true;
+}
+EXPORT_SYMBOL(drm_scdc_enable_scrambling);
+
+/**
+ * drm_scdc_disable_scrambling - disable scrambling
+ * @adapter: I2C adapter for DDC channel
+ *
+ * Write the TMDS config over SCDC channel, and disable scrambling
+ * Return: True if scrambling is successfully disabled, false otherwise.
+ */
+bool drm_scdc_disable_scrambling(struct i2c_adapter *adapter)
+{
+ u8 config;
+ int ret;
+
+ ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
+ if (ret < 0) {
+ DRM_ERROR("Failed to read tmds config, error %d\n", ret);
+ return false;
+ }
+
+ config &= ~SCDC_SCRAMBLING_ENABLE;
+
+ ret = drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config);
+ if (ret < 0) {
+ DRM_ERROR("Failed to enable scrambling, error %d\n", ret);
+ return false;
+ }
+
+ return true;
+}
+EXPORT_SYMBOL(drm_scdc_disable_scrambling);
+
+/**
+ * drm_scdc_set_high_tmds_clock_ratio - set TMDS clock ratio
+ * @adapter: I2C adapter for DDC channel
+ *
+ * Writes the TMDS config over SCDC channel, and sets TMDS
+ * clock ratio to 1/40
+ * Returns:
+ * True if write is successful, false otherwise.
+ */
+bool drm_scdc_set_high_tmds_clock_ratio(struct i2c_adapter *adapter)
+{
+ u8 config;
+ int ret;
+
+ ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
+ if (ret < 0) {
+ DRM_ERROR("Failed to read tmds config, err=%d\n", ret);
+ return false;
+ }
+
+ config |= SCDC_TMDS_BIT_CLOCK_RATIO_BY_40;
+
+ ret = drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config);
+ if (ret < 0) {
+ DRM_ERROR("Failed to set TMDS clock ratio, error %d\n", ret);
+ return false;
+ }
+
+ /*
+ * The spec says that the source should wait minimum 1ms and maximum
+ * 100ms after writing the TMDS config for clock ratio.
+ */
+ usleep_range(1000, 100000);
+ return true;
+}
+EXPORT_SYMBOL(drm_scdc_set_high_tmds_clock_ratio);
+
+/**
+ * drm_scdc_clear_high_tmds_clock_ratio - clear TMDS clock ratio
+ * @adapter: I2C adapter for DDC channel
+ *
+ * Writes the TMDS config over SCDC channel, and sets TMDS
+ * clock ratio back to 1/10 (from 1/40)
+ * Returns:
+ * True if write is successful, false otherwise.
+ */
+bool drm_scdc_clear_high_tmds_clock_ratio(struct i2c_adapter *adapter)
+{
+ u8 config;
+ int ret;
+
+ ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
+ if (ret < 0) {
+ DRM_ERROR("Failed to read tmds config, err=%d\n", ret);
+ return false;
+ }
+
+ config &= ~SCDC_TMDS_BIT_CLOCK_RATIO_BY_40;
+
+ ret = drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config);
+ if (ret < 0) {
+ DRM_ERROR("Failed to clear TMDS clock ratio, error %d\n", ret);
+ return false;
+ }
+
+ /*
+ * The spec says that the source should wait minimum 1ms and maximum
+ * 100ms after writing the TMDS config for clock ratio.
+ */
+ usleep_range(1000, 100000);
+ return true;
+}
+EXPORT_SYMBOL(drm_scdc_clear_high_tmds_clock_ratio);
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 6d5304e..78618308 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -90,6 +90,20 @@ enum subpixel_order {

};

+/**
+ * struct drm_scrambling: sink's scrambling support.
+ */
+struct drm_scrambling {
+ /**
+ * @supported: scrambling supported for rates > 340 Mhz.
+ */
+ bool supported;
+ /**
+ * @low_rates: scrambling supported for rates <= 340 Mhz.
+ */
+ bool low_rates;
+};
+
/*
* struct drm_scdc - Information about scdc capabilities of a HDMI 2.0 sink
*
@@ -105,8 +119,13 @@ struct drm_scdc {
* @read_request: sink is capable of generating scdc read request.
*/
bool read_request;
+ /**
+ * @scrambling: sink's scrambling capabilities
+ */
+ struct drm_scrambling scrambling;
};

+
/**
* struct drm_hdmi_info - runtime information about the connected HDMI sink
*
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index 43fb0ac..d24c974 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -462,5 +462,9 @@ void drm_edid_get_monitor_name(struct edid *edid, char *name,
struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
int hsize, int vsize, int fresh,
bool rb);
-
+bool drm_enable_scrambling(struct drm_connector *connector,
+ struct i2c_adapter *adapter, bool force);
+bool drm_disable_scrambling(struct drm_connector *connector,
+ struct i2c_adapter *adapter, bool force);
+bool drm_check_scrambling_status(struct i2c_adapter *adapter);
#endif /* __DRM_EDID_H__ */
diff --git a/include/drm/drm_scdc_helper.h b/include/drm/drm_scdc_helper.h
index 93b07bc..c5f2229 100644
--- a/include/drm/drm_scdc_helper.h
+++ b/include/drm/drm_scdc_helper.h
@@ -129,4 +129,45 @@ static inline int drm_scdc_writeb(struct i2c_adapter *adapter, u8 offset,
return drm_scdc_write(adapter, offset, &value, sizeof(value));
}

+/**
+ * drm_scdc_enable_scrambling - enable scrambling
+ * @adapter: I2C adapter for DDC channel
+ *
+ * Writes the TMDS config over SCDC channel, and enables scrambling
+ * Returns:
+ * True if scrambling is successfully enabled, false otherwise.
+ */
+
+bool drm_scdc_enable_scrambling(struct i2c_adapter *adapter);
+
+/**
+ * drm_scdc_disable_scrambling - disable scrambling
+ * @adapter: I2C adapter for DDC channel
+ *
+ * Write the TMDS config over SCDC channel, and disable scrambling
+ * Return: True if scrambling is successfully disabled, false otherwise.
+ */
+bool drm_scdc_disable_scrambling(struct i2c_adapter *adapter);
+
+/**
+ * drm_scdc_set_high_tmds_clock_ratio - set TMDS clock ratio
+ * @adapter: I2C adapter for DDC channel
+ *
+ * Writes the TMDS config over SCDC channel, and sets TMDS
+ * clock ratio to 1/40
+ * Returns:
+ * True if write is successful, false otherwise.
+ */
+bool drm_scdc_set_high_tmds_clock_ratio(struct i2c_adapter *adapter);
+
+/**
+ * drm_scdc_clear_high_tmds_clock_ratio - clear TMDS clock ratio
+ * @adapter: I2C adapter for DDC channel
+ *
+ * Writes the TMDS config over SCDC channel, and sets TMDS
+ * clock ratio back to 1/10 (from 1/40)
+ * Returns:
+ * True if write is successful, false otherwise.
+ */
+bool drm_scdc_clear_high_tmds_clock_ratio(struct i2c_adapter *adapter);
#endif
--
1.9.1