| Message ID | 20250108-drm-dp-msm-add-lttpr-transparent-mode-set-v4-1-918949bc2e3a@linaro.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | drm/dp: Rework LTTPR transparent mode handling and add support to msm driver | expand |
On Wed, Jan 08, 2025 at 04:31:43PM +0200, Abel Vesa wrote: > According to the DisplayPort standard, LTTPRs have two operating > modes: > - non-transparent - it replies to DPCD LTTPR field specific AUX > requests, while passes through all other AUX requests > - transparent - it passes through all AUX requests. > > Switching between this two modes is done by the DPTX by issuing > an AUX write to the DPCD PHY_REPEATER_MODE register. > > Add a generic helper that allows switching between these modes. > > Also add a generic wrapper for the helper that handles the explicit > disabling of non-transparent mode and its disable->enable sequence > mentioned in the DP Standard v2.0 section 3.6.6.1. Do this in order > to move this handling out of the vendor specific driver implementation > into the generic framework. > > Tested-by: Johan Hovold <johan+linaro@kernel.org> > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > Reviewed-by: Johan Hovold <johan+linaro@kernel.org> > Signed-off-by: Abel Vesa <abel.vesa@linaro.org> > --- > drivers/gpu/drm/display/drm_dp_helper.c | 62 +++++++++++++++++++++++++++++++++ > include/drm/display/drm_dp_helper.h | 2 ++ > 2 files changed, 64 insertions(+) > > diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c > index da3c8521a7fa7d3c9761377363cdd4b44ab1106e..fa7eff94d408718a1762834597f0cd51376d2596 100644 > --- a/drivers/gpu/drm/display/drm_dp_helper.c > +++ b/drivers/gpu/drm/display/drm_dp_helper.c > @@ -2817,6 +2817,68 @@ int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]) > } > EXPORT_SYMBOL(drm_dp_lttpr_max_link_rate); > > +/** > + * drm_dp_lttpr_set_transparent_mode - set the LTTPR in transparent mode kernel-doc functions should have () suffix > + * @aux: DisplayPort AUX channel > + * @enable: Enable or disable transparent mode > + * > + * Returns 0 on success or a negative error code on failure. And this should be "Return: ...". > + */ > +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable) > +{ > + u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT : > + DP_PHY_REPEATER_MODE_NON_TRANSPARENT; > + int ret = drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE, val); > + > + if (ret < 0) > + return ret; > + > + return (ret == 1) ? 0 : -EIO; > +} > +EXPORT_SYMBOL(drm_dp_lttpr_set_transparent_mode); > + > +/** > + * drm_dp_lttpr_init - init LTTPR transparency mode according to DP standard > + * Documentation also explicitly says not to leave a blank line here... Regards, Bjorn > + * @aux: DisplayPort AUX channel > + * @lttpr_count: Number of LTTPRs. Between 0 and 8, according to DP standard. > + * Negative error code for any non-valid number. > + * See drm_dp_lttpr_count(). > + * > + * Returns 0 on success or a negative error code on failure. > + */ > +int drm_dp_lttpr_init(struct drm_dp_aux *aux, int lttpr_count) > +{ > + int ret; > + > + if (!lttpr_count) > + return 0; > + > + /* > + * See DP Standard v2.0 3.6.6.1 about the explicit disabling of > + * non-transparent mode and the disable->enable non-transparent mode > + * sequence. > + */ > + ret = drm_dp_lttpr_set_transparent_mode(aux, true); > + if (ret) > + return ret; > + > + if (lttpr_count < 0) > + return -ENODEV; > + > + if (drm_dp_lttpr_set_transparent_mode(aux, false)) { > + /* > + * Roll-back to transparent mode if setting non-transparent > + * mode has failed > + */ > + drm_dp_lttpr_set_transparent_mode(aux, true); > + return -EINVAL; > + } > + > + return 0; > +} > +EXPORT_SYMBOL(drm_dp_lttpr_init); > + > /** > * drm_dp_lttpr_max_lane_count - get the maximum lane count supported by all LTTPRs > * @caps: LTTPR common capabilities > diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h > index 8f4054a560396a43750570a8c2e95624039ab8ad..3311df3b58255cf0620391d0948ccf6b569a8a34 100644 > --- a/include/drm/display/drm_dp_helper.h > +++ b/include/drm/display/drm_dp_helper.h > @@ -630,6 +630,8 @@ int drm_dp_read_lttpr_phy_caps(struct drm_dp_aux *aux, > u8 caps[DP_LTTPR_PHY_CAP_SIZE]); > int drm_dp_lttpr_count(const u8 cap[DP_LTTPR_COMMON_CAP_SIZE]); > int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]); > +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable); > +int drm_dp_lttpr_init(struct drm_dp_aux *aux, int lttpr_count); > int drm_dp_lttpr_max_lane_count(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]); > bool drm_dp_lttpr_voltage_swing_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]); > bool drm_dp_lttpr_pre_emphasis_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]); > > -- > 2.34.1 >
On 1/8/2025 6:31 AM, Abel Vesa wrote: > According to the DisplayPort standard, LTTPRs have two operating > modes: > - non-transparent - it replies to DPCD LTTPR field specific AUX > requests, while passes through all other AUX requests > - transparent - it passes through all AUX requests. > > Switching between this two modes is done by the DPTX by issuing > an AUX write to the DPCD PHY_REPEATER_MODE register. > > Add a generic helper that allows switching between these modes. > > Also add a generic wrapper for the helper that handles the explicit > disabling of non-transparent mode and its disable->enable sequence > mentioned in the DP Standard v2.0 section 3.6.6.1. Do this in order > to move this handling out of the vendor specific driver implementation > into the generic framework. > > Tested-by: Johan Hovold <johan+linaro@kernel.org> > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > Reviewed-by: Johan Hovold <johan+linaro@kernel.org> > Signed-off-by: Abel Vesa <abel.vesa@linaro.org> > --- > drivers/gpu/drm/display/drm_dp_helper.c | 62 +++++++++++++++++++++++++++++++++ > include/drm/display/drm_dp_helper.h | 2 ++ > 2 files changed, 64 insertions(+) > Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c index da3c8521a7fa7d3c9761377363cdd4b44ab1106e..fa7eff94d408718a1762834597f0cd51376d2596 100644 --- a/drivers/gpu/drm/display/drm_dp_helper.c +++ b/drivers/gpu/drm/display/drm_dp_helper.c @@ -2817,6 +2817,68 @@ int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]) } EXPORT_SYMBOL(drm_dp_lttpr_max_link_rate); +/** + * drm_dp_lttpr_set_transparent_mode - set the LTTPR in transparent mode + * @aux: DisplayPort AUX channel + * @enable: Enable or disable transparent mode + * + * Returns 0 on success or a negative error code on failure. + */ +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable) +{ + u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT : + DP_PHY_REPEATER_MODE_NON_TRANSPARENT; + int ret = drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE, val); + + if (ret < 0) + return ret; + + return (ret == 1) ? 0 : -EIO; +} +EXPORT_SYMBOL(drm_dp_lttpr_set_transparent_mode); + +/** + * drm_dp_lttpr_init - init LTTPR transparency mode according to DP standard + * + * @aux: DisplayPort AUX channel + * @lttpr_count: Number of LTTPRs. Between 0 and 8, according to DP standard. + * Negative error code for any non-valid number. + * See drm_dp_lttpr_count(). + * + * Returns 0 on success or a negative error code on failure. + */ +int drm_dp_lttpr_init(struct drm_dp_aux *aux, int lttpr_count) +{ + int ret; + + if (!lttpr_count) + return 0; + + /* + * See DP Standard v2.0 3.6.6.1 about the explicit disabling of + * non-transparent mode and the disable->enable non-transparent mode + * sequence. + */ + ret = drm_dp_lttpr_set_transparent_mode(aux, true); + if (ret) + return ret; + + if (lttpr_count < 0) + return -ENODEV; + + if (drm_dp_lttpr_set_transparent_mode(aux, false)) { + /* + * Roll-back to transparent mode if setting non-transparent + * mode has failed + */ + drm_dp_lttpr_set_transparent_mode(aux, true); + return -EINVAL; + } + + return 0; +} +EXPORT_SYMBOL(drm_dp_lttpr_init); + /** * drm_dp_lttpr_max_lane_count - get the maximum lane count supported by all LTTPRs * @caps: LTTPR common capabilities diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h index 8f4054a560396a43750570a8c2e95624039ab8ad..3311df3b58255cf0620391d0948ccf6b569a8a34 100644 --- a/include/drm/display/drm_dp_helper.h +++ b/include/drm/display/drm_dp_helper.h @@ -630,6 +630,8 @@ int drm_dp_read_lttpr_phy_caps(struct drm_dp_aux *aux, u8 caps[DP_LTTPR_PHY_CAP_SIZE]); int drm_dp_lttpr_count(const u8 cap[DP_LTTPR_COMMON_CAP_SIZE]); int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]); +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable); +int drm_dp_lttpr_init(struct drm_dp_aux *aux, int lttpr_count); int drm_dp_lttpr_max_lane_count(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]); bool drm_dp_lttpr_voltage_swing_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]); bool drm_dp_lttpr_pre_emphasis_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);