From: Shirish S s.shirish@samsung.com

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 --- drivers/gpu/drm/drm_edid.c | 19 ++++++++++++++++--- 1 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index bcc4725..7f62de5 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)