On Fri, 13 Mar 2015, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> When an i2c WRITE gets an i2c defer or short i2c ack reply, we are
> supposed to switch the request from I2C_WRITE to I2C_WRITE_STATUS_UPDATE
> when we continue to poll for the completion of the request.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
> drivers/gpu/drm/drm_dp_helper.c | 41
> +++++++++++++++++++++++++++++++++++++----
> 1 file changed, 37 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index d5368ea..4db81a6 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -422,6 +422,25 @@ static u32 drm_dp_i2c_functionality(struct i2c_adapter
> *adapter)
> I2C_FUNC_10BIT_ADDR;
> }
>
> +static void drm_dp_i2c_msg_set_request(struct drm_dp_aux_msg *msg,
> + const struct i2c_msg *i2c_msg)
> +{
> + msg->request = (i2c_msg->flags & I2C_M_RD) ?
> + DP_AUX_I2C_READ : DP_AUX_I2C_WRITE;
> + msg->request |= DP_AUX_I2C_MOT;
> +}
> +
> +static void drm_dp_i2c_msg_write_status_update(struct drm_dp_aux_msg *msg)
> +{
> + /*
> + * In case of i2c defer or short i2c ack reply to a write,
> + * we need to switch to WRITE_STATUS_UPDATE to drain the
> + * rest of the message
> + */
> + if ((msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_I2C_WRITE)
> + msg->request |= DP_AUX_I2C_WRITE_STATUS_UPDATE;
This only works because DP_AUX_I2C_WRITE == 0, and it may not be obvious
to the casual reader that DP_AUX_I2C_WRITE_STATUS_UPDATE is a
replacement not an addition to DP_AUX_I2C_WRITE.
Whether you fix that or not, this is
Reviewed-by: Jani Nikula <jani.nikula at intel.com>
> +}
> +
> /*
> * Transfer a single I2C-over-AUX message and handle various error
> conditions,
> * retrying the transaction as appropriate. It is assumed that the
> @@ -490,6 +509,8 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux,
> struct drm_dp_aux_msg *msg)
> * Both native ACK and I2C ACK replies received. We
> * can assume the transfer was successful.
> */
> + if (ret != msg->size)
> + drm_dp_i2c_msg_write_status_update(msg);
> return ret;
>
> case DP_AUX_I2C_REPLY_NACK:
> @@ -501,6 +522,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux,
> struct drm_dp_aux_msg *msg)
> DRM_DEBUG_KMS("I2C defer\n");
> aux->i2c_defer_count++;
> usleep_range(400, 500);
> + drm_dp_i2c_msg_write_status_update(msg);
> continue;
>
> default:
> @@ -566,10 +588,7 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter,
> struct i2c_msg *msgs,
>
> for (i = 0; i < num; i++) {
> msg.address = msgs[i].addr;
> - msg.request = (msgs[i].flags & I2C_M_RD) ?
> - DP_AUX_I2C_READ :
> - DP_AUX_I2C_WRITE;
> - msg.request |= DP_AUX_I2C_MOT;
> + drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
> /* Send a bare address packet to start the transaction.
> * Zero sized messages specify an address only (bare
> * address) transaction.
> @@ -577,6 +596,13 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter,
> struct i2c_msg *msgs,
> msg.buffer = NULL;
> msg.size = 0;
> err = drm_dp_i2c_do_msg(aux, &msg);
> +
> + /*
> + * Reset msg.request in case in case it got
> + * changed into a WRITE_STATUS_UPDATE.
> + */
> + drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
> +
> if (err < 0)
> break;
> /* We want each transaction to be as large as possible, but
> @@ -589,6 +615,13 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter,
> struct i2c_msg *msgs,
> msg.size = min(transfer_size, msgs[i].len - j);
>
> err = drm_dp_i2c_drain_msg(aux, &msg);
> +
> + /*
> + * Reset msg.request in case in case it got
> + * changed into a WRITE_STATUS_UPDATE.
> + */
> + drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
> +
> if (err < 0)
> break;
> transfer_size = err;
> --
> 2.0.5
>
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--
Jani Nikula, Intel Open Source Technology Center
