On Saturday 10 March 2018 03:53 AM, Enric Balletbo i Serra wrote:
> From: zain wang <wzz at rock-chips.com>
>
> According to DP spec v1.3 chap 3.5.1.2 Link Training, Link Policy Maker
> must first detect that the HPD signal is asserted high by the Downstream
> Device before establishing a link with it.
Reviewed-by: Archit Taneja <architt at codeaurora.org>
Thanks,
Archit
>
> Cc: St?phane Marchesin <marcheu at chromium.org>
> Signed-off-by: zain wang <wzz at rock-chips.com>
> Signed-off-by: Sean Paul <seanpaul at chromium.org>
> Signed-off-by: Thierry Escande <thierry.escande at collabora.com>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo at collabora.com>
> Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>
> ---
>
> drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> index c81733b8185e..92fb9a072cb6 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> @@ -1169,6 +1169,17 @@ static int analogix_dp_set_bridge(struct analogix_dp_device *dp)
> if (ret)
> goto out_dp_init;
>
> + /*
> + * According to DP spec v1.3 chap 3.5.1.2 Link Training,
> + * We should first make sure the HPD signal is asserted high by device
> + * when we want to establish a link with it.
> + */
> + ret = analogix_dp_detect_hpd(dp);
> + if (ret) {
> + DRM_ERROR("failed to get hpd single ret = %d\n", ret);
> + goto out_dp_init;
> + }
> +
> ret = analogix_dp_commit(dp);
> if (ret)
> goto out_dp_init;
>
