On Fri, Apr 04, 2014 at 10:40:57AM -0400, Alex Deucher wrote:
> We need bare address packets at the start and end of
> each i2c over aux transaction to properly reset the connection
> between transactions. This mirrors what the existing dp i2c
> over aux algo currently does.
>
> This fixes EDID fetches on certain monitors especially with
> dp bridges.
>
> Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
The i915 dp aux code will work the same way still, but curiously the hw
spec doesn't mention anything for this really. I didn't check tegra.
-Daniel
> ---
> drivers/gpu/drm/drm_dp_helper.c | 53 +++++++++++++++++++++++------------------
> 1 file changed, 30 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index f4babed..f0c2850 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -664,12 +664,26 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
> int num)
> {
> struct drm_dp_aux *aux = adapter->algo_data;
> - unsigned int i, j;
> + unsigned int m, b;
> + struct drm_dp_aux_msg msg;
> + int err = 0;
> + u8 buf = 0;
>
> - for (i = 0; i < num; i++) {
> - struct drm_dp_aux_msg msg;
> - int err;
> + memset(&msg, 0, sizeof(msg));
>
> + for (m = 0; m < num; m++) {
> + msg.address = msgs[m].addr;
> + msg.request = (msgs[m].flags & I2C_M_RD) ?
> + DP_AUX_I2C_READ :
> + DP_AUX_I2C_WRITE;
> + msg.request |= DP_AUX_I2C_MOT;
> + msg.buffer = &buf;
> + msg.size = 0;
> + err = drm_dp_i2c_do_msg(aux, &msg);
> + if (err < 0) {
> + printk("error %d in bare address write\n", err);
> + break;
> + }
> /*
> * Many hardware implementations support FIFOs larger than a
> * single byte, but it has been empirically determined that
> @@ -677,31 +691,24 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
> * decreased performance. Therefore each message is simply
> * transferred byte-by-byte.
> */
> - for (j = 0; j < msgs[i].len; j++) {
> - memset(&msg, 0, sizeof(msg));
> - msg.address = msgs[i].addr;
> -
> - msg.request = (msgs[i].flags & I2C_M_RD) ?
> - DP_AUX_I2C_READ :
> - DP_AUX_I2C_WRITE;
> -
> - /*
> - * All messages except the last one are middle-of-
> - * transfer messages.
> - */
> - if ((i < num - 1) || (j < msgs[i].len - 1))
> - msg.request |= DP_AUX_I2C_MOT;
> -
> - msg.buffer = msgs[i].buf + j;
> + for (b = 0; b < msgs[m].len; b++) {
> + msg.buffer = msgs[m].buf + b;
> msg.size = 1;
>
> err = drm_dp_i2c_do_msg(aux, &msg);
> if (err < 0)
> - return err;
> + break;
> }
> }
> -
> - return num;
> + if (err >= 0)
> + err = num;
> + /* send a bare address packet to close out the connection */
> + msg.request &= ~DP_AUX_I2C_MOT;
> + msg.buffer = &buf;
> + msg.size = 0;
> + (void)drm_dp_i2c_do_msg(aux, &msg);
> +
> + return err;
> }
>
> static const struct i2c_algorithm drm_dp_i2c_algo = {
> --
> 1.8.3.1
>
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> http://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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