On Tue, Aug 21, 2012 at 9:10 AM, Shirish S <s.shirish@xxxxxxxxxxx> wrote:
> 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@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_edid.c | 17 ++++++++++++-----
> 1 files changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index a8743c3..2c2996e 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;
Have you tested this on i915 with gmbus enabled? I'm asking since we
don't implement the IGNORE_NAK flag and hence I'd expect spurious
failures on displays that don't support E-DDC ...
Cheers, Daniel
> int ret, retries = 5;
>
> /* The core i2c driver will automatically retry the transfer if the
> @@ -264,27 +266,32 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
> */
> do {
> struct i2c_msg msgs[] = {
> - {
> + { /*set segment pointer */
> + .addr = DDC_SEGMENT_ADDR,
> + .flags = segFlags,
> + .len = 1,
> + .buf = &start,
> + }, { /*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, 2);
> + ret = i2c_transfer(adapter, msgs, 3);
> if (ret == -ENXIO) {
> DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n",
> adapter->name);
> break;
> }
> - } while (ret != 2 && --retries);
> + } while (ret != 3 && --retries);
>
> - return ret == 2 ? 0 : -1;
> + return ret == 3 ? 0 : -1;
> }
>
> static bool drm_edid_is_zero(u8 *in_edid, int length)
> --
> 1.7.0.4
>
> _______________________________________________
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> http://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
daniel.vetter@xxxxxxxx - +41 (0) 79 364 57 48 - http://blog.ffwll.ch
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