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authorShirish S <s.shirish@samsung.com>2012-08-30 07:04:06 +0000
committerDave Airlie <airlied@redhat.com>2012-09-13 11:28:59 +1000
commitcd004b3f4cd4169815c82bf9e424fda06978898a (patch)
tree937c4b7676e7f375bb3cc6ad9833b17123a10c13 /drivers/gpu/drm/drm_edid.c
parent93eb58d53fb14e9eeb1b42f8c04dbd7afc09adf7 (diff)
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>
Diffstat (limited to 'drivers/gpu/drm/drm_edid.c')
-rw-r--r--drivers/gpu/drm/drm_edid.c19
1 files changed, 16 insertions, 3 deletions
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 265a0862a961..acb489ff3630 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -254,6 +254,8 @@ drm_do_probe_ddc_edid(struct i2c_adapter *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
@@ -265,6 +267,11 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
do {
struct i2c_msg msgs[] = {
{
+ .addr = DDC_SEGMENT_ADDR,
+ .flags = 0,
+ .len = 1,
+ .buf = &segment,
+ }, {
.addr = DDC_ADDR,
.flags = 0,
.len = 1,
@@ -276,15 +283,21 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
.buf = buf,
}
};
- ret = i2c_transfer(adapter, msgs, 2);
+
+ /*
+ * Avoid sending the segment addr to not upset non-compliant ddc
+ * monitors.
+ */
+ ret = i2c_transfer(adapter, &msgs[3 - xfers], xfers);
+
if (ret == -ENXIO) {
DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n",
adapter->name);
break;
}
- } while (ret != 2 && --retries);
+ } while (ret != xfers && --retries);
- return ret == 2 ? 0 : -1;
+ return ret == xfers ? 0 : -1;
}
static bool drm_edid_is_zero(u8 *in_edid, int length)