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 --- drivers/gpu/drm/drm_edid.c | 83 ++++++++++++++++++++++++++++++++----------- 1 files changed, 62 insertions(+), 21 deletions(-)
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index a8743c3..a10a130 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 short segFlags = segment ? 0 : I2C_M_IGNORE_NAK; int ret, retries = 5;
/* The core i2c driver will automatically retry the transfer if the @@ -262,29 +264,68 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf, * generate spurious NAKs and timeouts. Retrying the transfer * of the individual block a few times seems to overcome this. */ - do { - struct i2c_msg msgs[] = { - { - .addr = DDC_ADDR, - .flags = 0, - .len = 1, - .buf = &start, - }, { - .addr = DDC_ADDR, - .flags = I2C_M_RD, - .len = len, - .buf = buf, + switch (segment) { + /* To reduce traffic on I2C, we request the i2c xfer + * for segment addr only if 4 block edid data is + * present. + * 0 : DDC + * 1 : E-DDC + */ + case 0: + do { + struct i2c_msg msgs[] = { + { + .addr = DDC_ADDR, + .flags = 0, + .len = 1, + .buf = &start, + }, { + .addr = DDC_ADDR, + .flags = I2C_M_RD, + .len = len, + .buf = buf, + } + }; + ret = i2c_transfer(adapter, msgs, 2); + if (ret == -ENXIO) { + DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n", + adapter->name); + break; } - }; - ret = i2c_transfer(adapter, msgs, 2); - if (ret == -ENXIO) { - DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n", - adapter->name); - break; - } - } while (ret != 2 && --retries); + } while (ret != 2 && --retries); + + return ret == 2 ? 0 : -1; + case 1: + do { + struct i2c_msg msgs[] = { + { /*set segment pointer */ + .addr = DDC_SEGMENT_ADDR, + .flags = segFlags, + .len = 1, + .buf = &segment, + }, { /*set offset */ + .addr = DDC_ADDR, + .flags = 0, + .len = 1, + .buf = &start, + }, { /*set data */ + .addr = DDC_ADDR, + .flags = I2C_M_RD, + .len = len, + .buf = buf, + } + }; + ret = i2c_transfer(adapter, msgs, 3); + if (ret == -ENXIO) { + DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n", + adapter->name); + break; + } + } while (ret != 3 && --retries);
- return ret == 2 ? 0 : -1; + return ret == 3 ? 0 : -1; + } + return -1; }
static bool drm_edid_is_zero(u8 *in_edid, int length)