On Tue, Jan 14, 2014 at 9:55 AM, Thierry Reding
<thierry.reding@xxxxxxxxx> wrote:
> Add a helper to probe a DP link (read out the supported DPCD revision,
> maximum rate, link count and capabilities) as well as power up the DP
> link and configure it accordingly.
>
> Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
> ---
> Changes in v3:
> - split into drm_dp_link_power_up() and drm_dp_link_configure()
> - do not change sink state for DPCD versions earlier than 1.1
> - sleep for 1-2 ms after setting local sink to D0 state
> - read and write consecutive registers where possible
> - read DPCD revision when link is probed
> - remove duplicate kerneldoc
>
> drivers/gpu/drm/drm_dp_helper.c | 94 +++++++++++++++++++++++++++++++++++++++++
> include/drm/drm_dp_helper.h | 17 ++++++++
> 2 files changed, 111 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 572637456713..ac2e12789634 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -472,3 +472,97 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
> DP_LINK_STATUS_SIZE);
> }
> EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
> +
> +/**
> + * drm_dp_link_probe() - probe a DisplayPort link for capabilities
> + * @aux: DisplayPort AUX channel
> + * @link: pointer to structure in which to return link capabilities
> + *
> + * The structure filled in by this function can usually be passed directly
> + * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and
> + * configure the link based on the link's capabilities.
> + *
> + * Returns 0 on success or a negative error code on failure.
> + */
> +int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
> +{
> + u8 values[3];
> + int err;
> +
> + memset(link, 0, sizeof(*link));
> +
> + err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values));
> + if (err < 0)
> + return err;
> +
> + link->revision = values[0];
> + link->rate = drm_dp_bw_code_to_link_rate(values[1]);
> + link->num_lanes = values[2] & DP_MAX_LANE_COUNT_MASK;
> +
> + if (values[2] & DP_ENHANCED_FRAME_CAP)
> + link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING;
> +
> + return 0;
> +}
> +
> +/**
> + * drm_dp_link_power_up() - power up a DisplayPort link
> + * @aux: DisplayPort AUX channel
> + * @link: pointer to a structure containing the link configuration
> + *
> + * Returns 0 on success or a negative error code on failure.
> + */
> +int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link)
> +{
> + u8 value;
> + int err;
> +
> + /* DP_SET_POWER register is only available on DPCD v1.1 and later */
> + if (link->revision < 0x11)
> + return 0;
> +
> + err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
> + if (err < 0)
> + return err;
> +
> + value &= ~DP_SET_POWER_MASK;
> + value |= DP_SET_POWER_D0;
> +
> + err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
> + if (err < 0)
> + return err;
> +
> + /*
> + * According to the DP 1.1 specification, a "Sink Device must exit the
> + * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink
> + * Control Field" (register 0x600).
> + */
> + usleep_range(1000, 2000);
> +
> + return 0;
> +}
> +
> +/**
> + * drm_dp_link_configure() - configure a DisplayPort link
> + * @aux: DisplayPort AUX cahnnel
> + * @link: pointer to a structure containing the link configuration
> + *
> + * Returns 0 on seccuss or a negative error code on failure.
spelling. success.
Alex
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