On Tue, Jan 14, 2014 at 9:55 AM, Thierry Reding thierry.reding@gmail.com 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@nvidia.com
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