On Mon, Aug 21, 2017 at 06:55:47PM +0530, Shashank Sharma wrote:
> It's an observation during some CI tests that few LSPCON chips
> respond slow while system is under load, and need some delay
> while reading current mode status using i2c-over-aux channel.
>
> This patch:
> - Adds few retries and delays before declaring a read
> failure from LSPCON hardware.
> - Changes the debug level of the print from ERROR->DEBUG
> whereas another patch in I915 will add an ERROR message
> from the caller when we have timed out all our limits.
>
> V2: addressed review comments from Imre, and added r-b
> - use int instead of u8 for counter
> - use for loop instead of do...while();
>
> Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: Imre Deak <imre.deak@xxxxxxxxx>
>
> Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx>
> Signed-off-by: Shashank Sharma <shashank.sharma@xxxxxxxxx>
> Signed-off-by: Mahesh Kumar <mahesh1.kumar@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_dp_dual_mode_helper.c | 14 +++++++++++---
> 1 file changed, 11 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 80e62f6..fc8c7ac 100644
> --- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> @@ -409,6 +409,7 @@ int drm_lspcon_get_mode(struct i2c_adapter *adapter,
> enum drm_lspcon_mode *mode)
> {
> u8 data;
> + int retry;
> int ret = 0;
>
> if (!mode) {
> @@ -417,10 +418,17 @@ 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 = 5; ; retry--) {
Ok, confused myself with my original suggestion to include above the
condition for retry too. That could add an extraneous delay if all the
transfers fail as you explained on IRC.
I think this is still a bit clearer than the do {} while() loop so let's
go with this version.
> + ret = drm_dp_dual_mode_read(adapter,
> + DP_DUAL_MODE_LSPCON_CURRENT_MODE,
> + &data, sizeof(data));
> + if (!ret || !retry)
> + break;
> + usleep_range(500, 1000);
> + }
> +
> 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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