Add a helper to probe a DP link (reading out the maximum rate, link count and capabilities) as well as configuring it accordingly.
Signed-off-by: Thierry Reding treding@nvidia.com --- drivers/gpu/drm/drm_dp_helper.c | 77 +++++++++++++++++++++++++++++++++++++++++ include/drm/drm_dp_helper.h | 30 ++++++++++++++++ 2 files changed, 107 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 8111b8e5a8bc..01a8173c6e83 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -478,3 +478,80 @@ 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() 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 value; + int err; + + memset(link, 0, sizeof(*link)); + + err = drm_dp_dpcd_readb(aux, DP_MAX_LINK_RATE, &value); + if (err < 0) + return err; + + link->rate = drm_dp_bw_code_to_link_rate(value); + + err = drm_dp_dpcd_readb(aux, DP_MAX_LANE_COUNT, &value); + if (err < 0) + return err; + + link->num_lanes = value & DP_MAX_LANE_COUNT_MASK; + + if (value & DP_ENHANCED_FRAME_CAP) + link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING; + + return 0; +} + +/** + * drm_dp_link_power_up() - power up and configure 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; + + 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, value, DP_SET_POWER); + if (err < 0) + return err; + + value = drm_dp_link_rate_to_bw_code(link->rate); + + err = drm_dp_dpcd_writeb(aux, value, DP_LINK_BW_SET); + if (err < 0) + return err; + + value = link->num_lanes; + + if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING) + value |= DP_LANE_COUNT_ENHANCED_FRAME_EN; + + err = drm_dp_dpcd_writeb(aux, value, DP_LANE_COUNT_SET); + if (err < 0) + return err; + + return 0; +} diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index 38cbaef05005..bad9ee11a2e2 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -290,6 +290,7 @@ #define DP_SET_POWER 0x600 # define DP_SET_POWER_D0 0x1 # define DP_SET_POWER_D3 0x2 +# define DP_SET_POWER_MASK 0x3
#define DP_PSR_ERROR_STATUS 0x2006 /* XXX 1.2? */ # define DP_PSR_LINK_CRC_ERROR (1 << 0) @@ -464,4 +465,33 @@ static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux, u8 value, int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux, u8 status[DP_LINK_STATUS_SIZE]);
+/* + * DisplayPort link + */ +#define DP_LINK_CAP_ENHANCED_FRAMING (1 << 0) + +struct drm_dp_link { + unsigned int rate; + unsigned int num_lanes; + unsigned long capabilities; +}; + +/** + * drm_dp_link_probe() - probe link properties and capabilities + * @aux: DisplayPort AUX channel + * @link: DisplayPort link + * + * 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); + +/** + * drm_dp_link_power_up() - power up a link + * @aux: DisplayPort AUX channel + * @link: DisplayPort link + * + * 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); + #endif /* _DRM_DP_HELPER_H_ */