drm/sun4i: hdmi: Implement I2C adapter for A10s DDC bus

The documentation for drm_do_get_edid in drivers/gpu/drm/drm_edid.c states:
"As in the general case the DDC bus is accessible by the kernel at the I2C
level, drivers must make all reasonable efforts to expose it as an I2C
adapter and use drm_get_edid() instead of abusing this function."

Exposing the DDC bus as an I2C adapter is more beneficial as it can be used
for purposes other than reading the EDID such as modifying the EDID or
using the HDMI DDC pins as an I2C bus through the I2C dev interface from
userspace (e.g. i2c-tools).

Implement this for A10s.

Signed-off-by: Jonathan Liu <net147@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

1 files changed, 11 insertions, 90 deletions

diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
index d3398f6250ef..b74607feb35c 100644
--- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
+++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
@@ -29,8 +29,6 @@
 #include "sun4i_hdmi.h"
 #include "sun4i_tcon.h"
 
-#define DDC_SEGMENT_ADDR	0x30
-
 static inline struct sun4i_hdmi *
 drm_encoder_to_sun4i_hdmi(struct drm_encoder *encoder)
 {
@@ -184,93 +182,13 @@ static const struct drm_encoder_funcs sun4i_hdmi_funcs = {
 	.destroy	= drm_encoder_cleanup,
 };
 
-static int sun4i_hdmi_read_sub_block(struct sun4i_hdmi *hdmi,
-				     unsigned int blk, unsigned int offset,
-				     u8 *buf, unsigned int count)
-{
-	unsigned long reg;
-	int i;
-
-	reg = readl(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
-	reg &= ~SUN4I_HDMI_DDC_CTRL_FIFO_DIR_MASK;
-	writel(reg | SUN4I_HDMI_DDC_CTRL_FIFO_DIR_READ,
-	       hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
-
-	writel(SUN4I_HDMI_DDC_ADDR_SEGMENT(offset >> 8) |
-	       SUN4I_HDMI_DDC_ADDR_EDDC(DDC_SEGMENT_ADDR << 1) |
-	       SUN4I_HDMI_DDC_ADDR_OFFSET(offset) |
-	       SUN4I_HDMI_DDC_ADDR_SLAVE(DDC_ADDR),
-	       hdmi->base + SUN4I_HDMI_DDC_ADDR_REG);
-
-	reg = readl(hdmi->base + SUN4I_HDMI_DDC_FIFO_CTRL_REG);
-	writel(reg | SUN4I_HDMI_DDC_FIFO_CTRL_CLEAR,
-	       hdmi->base + SUN4I_HDMI_DDC_FIFO_CTRL_REG);
-
-	writel(count, hdmi->base + SUN4I_HDMI_DDC_BYTE_COUNT_REG);
-	writel(SUN4I_HDMI_DDC_CMD_EXPLICIT_EDDC_READ,
-	       hdmi->base + SUN4I_HDMI_DDC_CMD_REG);
-
-	reg = readl(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
-	writel(reg | SUN4I_HDMI_DDC_CTRL_START_CMD,
-	       hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
-
-	if (readl_poll_timeout(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG, reg,
-			       !(reg & SUN4I_HDMI_DDC_CTRL_START_CMD),
-			       100, 100000))
-		return -EIO;
-
-	for (i = 0; i < count; i++)
-		buf[i] = readb(hdmi->base + SUN4I_HDMI_DDC_FIFO_DATA_REG);
-
-	return 0;
-}
-
-static int sun4i_hdmi_read_edid_block(void *data, u8 *buf, unsigned int blk,
-				      size_t length)
-{
-	struct sun4i_hdmi *hdmi = data;
-	int retry = 2, i;
-
-	do {
-		for (i = 0; i < length; i += SUN4I_HDMI_DDC_FIFO_SIZE) {
-			unsigned char offset = blk * EDID_LENGTH + i;
-			unsigned int count = min((unsigned int)SUN4I_HDMI_DDC_FIFO_SIZE,
-						 length - i);
-			int ret;
-
-			ret = sun4i_hdmi_read_sub_block(hdmi, blk, offset,
-							buf + i, count);
-			if (ret)
-				return ret;
-		}
-	} while (!drm_edid_block_valid(buf, blk, true, NULL) && (retry--));
-
-	return 0;
-}
-
 static int sun4i_hdmi_get_modes(struct drm_connector *connector)
 {
 	struct sun4i_hdmi *hdmi = drm_connector_to_sun4i_hdmi(connector);
-	unsigned long reg;
 	struct edid *edid;
 	int ret;
 
-	/* Reset i2c controller */
-	writel(SUN4I_HDMI_DDC_CTRL_ENABLE | SUN4I_HDMI_DDC_CTRL_RESET,
-	       hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
-	if (readl_poll_timeout(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG, reg,
-			       !(reg & SUN4I_HDMI_DDC_CTRL_RESET),
-			       100, 2000))
-		return -EIO;
-
-	writel(SUN4I_HDMI_DDC_LINE_CTRL_SDA_ENABLE |
-	       SUN4I_HDMI_DDC_LINE_CTRL_SCL_ENABLE,
-	       hdmi->base + SUN4I_HDMI_DDC_LINE_CTRL_REG);
-
-	clk_prepare_enable(hdmi->ddc_clk);
-	clk_set_rate(hdmi->ddc_clk, 100000);
-
-	edid = drm_do_get_edid(connector, sun4i_hdmi_read_edid_block, hdmi);
+	edid = drm_get_edid(connector, hdmi->i2c);
 	if (!edid)
 		return 0;
 
@@ -282,8 +200,6 @@ static int sun4i_hdmi_get_modes(struct drm_connector *connector)
 	ret = drm_add_edid_modes(connector, edid);
 	kfree(edid);
 
-	clk_disable_unprepare(hdmi->ddc_clk);
-
 	return ret;
 }
 
@@ -407,9 +323,9 @@ static int sun4i_hdmi_bind(struct device *dev, struct device *master,
 		SUN4I_HDMI_PLL_CTRL_PLL_EN;
 	writel(reg, hdmi->base + SUN4I_HDMI_PLL_CTRL_REG);
 
-	ret = sun4i_ddc_create(hdmi, hdmi->tmds_clk);
+	ret = sun4i_hdmi_i2c_create(dev, hdmi);
 	if (ret) {
-		dev_err(dev, "Couldn't create the DDC clock\n");
+		dev_err(dev, "Couldn't create the HDMI I2C adapter\n");
 		return ret;
 	}
 
@@ -422,13 +338,15 @@ static int sun4i_hdmi_bind(struct device *dev, struct device *master,
 			       NULL);
 	if (ret) {
 		dev_err(dev, "Couldn't initialise the HDMI encoder\n");
-		return ret;
+		goto err_del_i2c_adapter;
 	}
 
 	hdmi->encoder.possible_crtcs = drm_of_find_possible_crtcs(drm,
 								  dev->of_node);
-	if (!hdmi->encoder.possible_crtcs)
-		return -EPROBE_DEFER;
+	if (!hdmi->encoder.possible_crtcs) {
+		ret = -EPROBE_DEFER;
+		goto err_del_i2c_adapter;
+	}
 
 	drm_connector_helper_add(&hdmi->connector,
 				 &sun4i_hdmi_connector_helper_funcs);
@@ -451,6 +369,8 @@ static int sun4i_hdmi_bind(struct device *dev, struct device *master,
 
 err_cleanup_connector:
 	drm_encoder_cleanup(&hdmi->encoder);
+err_del_i2c_adapter:
+	i2c_del_adapter(hdmi->i2c);
 	return ret;
 }
 
@@ -461,6 +381,7 @@ static void sun4i_hdmi_unbind(struct device *dev, struct device *master,
 
 	drm_connector_cleanup(&hdmi->connector);
 	drm_encoder_cleanup(&hdmi->encoder);
+	i2c_del_adapter(hdmi->i2c);
 }
 
 static const struct component_ops sun4i_hdmi_ops = {