On Tue, Oct 10, 2017 at 03:37:42PM +0530, Shashank Sharma wrote:
> From the CI builds, its been observed that during a driver
> reload/insert, dp dual mode read function sometimes fails to
> read from LSPCON device over i2c-over-aux channel.
>
> This patch:
> - adds some delay and few retries, allowing a scope for these
> devices to settle down and respond.
> - changes one error log's level from ERROR->DEBUG as we want
> to call it an error only after all the retries are exhausted.
>
> V2: Addressed review comments from Jani (for loop for retry)
> V3: Addressed review comments from Imre (break on partial read too)
> V3: Addressed review comments from Ville/Imre (Add the retries
> exclusively for LSPCON, not for all dp_dual_mode devices)
>
> Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: Imre Deak <imre.deak@xxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Signed-off-by: Shashank Sharma <shashank.sharma@xxxxxxxxx>
Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_dp_dual_mode_helper.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> index 0ef9011..02a5092 100644
> --- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> @@ -410,6 +410,7 @@ int drm_lspcon_get_mode(struct i2c_adapter *adapter,
> {
> u8 data;
> int ret = 0;
> + int retry;
>
> if (!mode) {
> DRM_ERROR("NULL input\n");
> @@ -417,10 +418,19 @@ int drm_lspcon_get_mode(struct i2c_adapter *adapter,
> }
>
> /* Read Status: i2c over aux */
> - ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE,
> - &data, sizeof(data));
> + for (retry = 0; retry < 6; retry++) {
> + if (retry)
> + usleep_range(500, 1000);
> +
> + ret = drm_dp_dual_mode_read(adapter,
> + DP_DUAL_MODE_LSPCON_CURRENT_MODE,
> + &data, sizeof(data));
> + if (!ret)
> + break;
> + }
> +
> if (ret < 0) {
> - DRM_ERROR("LSPCON read(0x80, 0x41) failed\n");
> + DRM_DEBUG_KMS("LSPCON read(0x80, 0x41) failed\n");
> return -EFAULT;
> }
>
> --
> 2.7.4
>
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