[PATCH v7 4/6] drm/edid: detect SCDC support in HF-VSDB

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

This patch does following:
- Adds a new structure (drm_hdmi_info) in drm_display_info.
  This structure will be used to save and indicate if sink
  supports advanced HDMI 2.0 features
- Adds another structure drm_scdc within drm_hdmi_info, to
  reflect scdc support and capabilities in connected HDMI 2.0 sink.
- Checks the HF-VSDB block for presence of SCDC, and marks it
  in scdc structure
- If SCDC is present, checks if sink is capable of generating
  SCDC read request, and marks it in scdc structure.

V2: Addressed review comments
  Thierry:
  - Fix typos in commit message and make abbreviation consistent
    across the commit message.
  - Change structure object name from hdmi_info -> hdmi
  - Fix typos and abbreviations in description of structure drm_hdmi_info
    end the description with a full stop.
  - Create a structure drm_scdc, and keep all information related to SCDC
    register set (supported, read request supported) etc in it.

  Ville:
  - Change rr -> read_request
  - Call drm_detect_scrambling function drm_parse_hf_vsdb so that all
    of HF-VSDB parsing can be kept in same function, in incremental
    patches.

V3: Rebase.
V4: Rebase.
V5: Rebase.
V6: Addressed review comments from Ville
  - Add clock rate calculations for 1/10 and 1/40 ratios
  - Remove leftovers from old patchset
V7: Added R-B from Jose.

Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Jose Abreu <joabreu@synopsys.com>
---
 drivers/gpu/drm/drm_edid.c        |  33 ++++++++++-
 drivers/gpu/drm/drm_scdc_helper.c | 121 ++++++++++++++++++++++++++++++++++++++
 include/drm/drm_connector.h       |  19 ++++++
 include/drm/drm_edid.h            |   1 -
 include/drm/drm_scdc_helper.h     |  27 +++++++++
 5 files changed, 199 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index d64b7bd..fad3d44 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"
 
@@ -3820,13 +3821,43 @@ 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 c2dd33f..3cd96a9 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
@@ -121,3 +123,122 @@ ssize_t drm_scdc_write(struct i2c_adapter *adapter, u8 offset,
 	return 0;
 }
 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_get_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_get_scrambling_status);
+
+/**
+ * drm_scdc_set_scrambling - enable scrambling
+ * @adapter: I2C adapter for DDC channel
+ * @enable: bool to indicate if scrambling is to be enabled/disabled
+ *
+ * Writes the TMDS config register over SCDC channel, and:
+ * enables scrambling when enable = 1
+ * disables scrambling when enable = 0
+ *
+ * Returns:
+ * True if scrambling is set/reset successfully, false otherwise.
+ */
+
+bool drm_scdc_set_scrambling(struct i2c_adapter *adapter, bool enable)
+{
+	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;
+	}
+
+	if (enable)
+		config |= SCDC_SCRAMBLING_ENABLE;
+	else
+		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_set_scrambling);
+
+/**
+ * drm_scdc_set_high_tmds_clock_ratio - set TMDS clock ratio
+ * @adapter: I2C adapter for DDC channel
+ * @set: ret or reset the high clock ratio
+ *
+ * TMDS clock ratio calculations go like this:
+ * TMDS character = 10 bit TMDS encoded value
+ * TMDS character rate = The rate at which TMDS characters are transmitted(Mcsc)
+ * TMDS bit rate = 10x TMDS character rate
+ * As per the spec:
+ * TMDS clock rate for pixel clock < 340 MHz = 1x the character rate
+ *	= 1/10 pixel clock rate
+ * TMDS clock rate for pixel clock > 340 MHz = 0.25x the character rate
+ *	= 1/40 pixel clock rate
+ *
+ * Writes to the TMDS config register over SCDC channel, and:
+ * sets TMDS clock ratio to 1/40 when set = 1
+ * sets TMDS clock ratio to 1/10 when set = 0
+ *
+ * Returns:
+ * True if write is successful, false otherwise.
+ */
+bool drm_scdc_set_high_tmds_clock_ratio(struct i2c_adapter *adapter, bool set)
+{
+	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;
+	}
+
+	if (set)
+		config |= SCDC_TMDS_BIT_CLOCK_RATIO_BY_40;
+	else
+		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 a source should wait minimum 1ms and maximum
+	 * 100ms after writing the TMDS config for clock ratio. Lets allow a
+	 * wait of upto 2ms here.
+	 */
+	usleep_range(1000, 2000);
+	return true;
+}
+EXPORT_SYMBOL(drm_scdc_set_high_tmds_clock_ratio);
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index bf9d6f5..f8b766d 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 3ead84d..7b9f48b 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -476,5 +476,4 @@ 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);
-
 #endif /* __DRM_EDID_H__ */
diff --git a/include/drm/drm_scdc_helper.h b/include/drm/drm_scdc_helper.h
index 9c52deb..ab6bcfb 100644
--- a/include/drm/drm_scdc_helper.h
+++ b/include/drm/drm_scdc_helper.h
@@ -129,4 +129,31 @@ static inline int drm_scdc_writeb(struct i2c_adapter *adapter, u8 offset,
 	return drm_scdc_write(adapter, offset, &value, sizeof(value));
 }
 
+/**
+ * drm_scdc_set_scrambling - enable scrambling
+ * @adapter: I2C adapter for DDC channel
+ * @enable: bool to indicate if scrambling is to be enabled/disabled
+ *
+ * Writes the TMDS config register over SCDC channel, and:
+ * enables scrambling when enable = 1
+ * disables scrambling when enable = 0
+ *
+ * Returns:
+ * True if scrambling is set/reset successfully, false otherwise.
+ */
+bool drm_scdc_set_scrambling(struct i2c_adapter *adapter, bool enable);
+
+/**
+ * drm_scdc_set_high_tmds_clock_ratio - set TMDS clock ratio
+ * @adapter: I2C adapter for DDC channel
+ * @set: ret or reset the high clock ratio
+ *
+ * Writes to the TMDS config register over SCDC channel, and:
+ * sets TMDS clock ratio to 1/40 when set = 1
+ * sets TMDS clock ratio to 1/10 when set = 0
+ *
+ * Returns:
+ * True if write is successful, false otherwise.
+ */
+bool drm_scdc_set_high_tmds_clock_ratio(struct i2c_adapter *adapter, bool set);
 #endif
-- 
1.9.1

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