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

[Shashank Sharma <shashank.sharma@intel.com>]

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

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