drm: Import Linux commit cd004b3f4cd4169815c82bf9e424fda06978898a

Author: Shirish S <s.shirish@samsung.com>
Date:   Thu Aug 30 07:04:06 2012 +0000

    drm: edid: add support for E-DDC

    The current logic for probing ddc is limited to
    2 blocks (256 bytes), this patch adds support
    for the 4 block (512) data.

    To do this, a single 8-bit segment index is
    passed to the display via the I2C address 30h.
    Data from the selected segment is then immediately
    read via the regular DDC2 address using a repeated
    I2C 'START' signal.

    Signed-off-by: Shirish S <s.shirish@samsung.com>
    Reviewed-by: Jean Delvare <jdelvare@suse.de>
    Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    Reviewed-by: Ville Syrjala <ville.syrjala@linux.intel.com>
    Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/sys/dev/drm2/drm_edid.c b/sys/dev/drm2/drm_edid.c
index 827677d..86306b9 100644
--- a/sys/dev/drm2/drm_edid.c
+++ b/sys/dev/drm2/drm_edid.c
@@ -253,6 +253,8 @@ drm_do_probe_ddc_edid(device_t adapter, unsigned char *buf,
 		      int block, int len)
 {
 	unsigned char start = block * EDID_LENGTH;
+	unsigned char segment = block >> 1;
+	unsigned char xfers = segment ? 3 : 2;
 	int ret, retries = 5;
 
 	/* The core i2c driver will automatically retry the transfer if the
@@ -264,6 +266,11 @@ drm_do_probe_ddc_edid(device_t adapter, unsigned char *buf,
 	do {
 		struct iic_msg msgs[] = {
 			{
+				.slave  = DDC_SEGMENT_ADDR << 1,
+				.flags  = 0,
+				.len    = 1,
+				.buf    = &segment,
+			}, {
 				.slave	= DDC_ADDR << 1,
 				.flags	= IIC_M_WR,
 				.len	= 1,
@@ -275,7 +282,13 @@ drm_do_probe_ddc_edid(device_t adapter, unsigned char *buf,
 				.buf	= buf,
 			}
 		};
-		ret = iicbus_transfer(adapter, msgs, 2);
+
+	/*
+	 * Avoid sending the segment addr to not upset non-compliant ddc
+	 * monitors.
+	 */
+		ret = iicbus_transfer(adapter, &msgs[3 - xfers], xfers);
+
 		if (ret != 0)
 			DRM_DEBUG_KMS("iicbus_transfer countdown %d error %d\n",
 			    retries, ret);