On Di, 2026-07-28 at 18:23 +0530, Yashas D wrote: > This series adds 'no-hpd' device tree property support to the Cadence > MHDP8546 bridge driver for boards where the HPD line cannot be used > for > hotplug detection. > > On TI J721S2 EVMs, the HPD signal is routed to SoC pin AA24 > (MCASP1_ACLKX/DP0_HPD). This pin is muxed with the McASP1 audio bit > clock; selecting DP0_HPD breaks audio. There is no alternative pin > carrying the HPD signal which makes it impossible to use HPD > without loosing the audio capabilities. Hi Yashas,
this description is not correct. On the J721S2 EVM the pin AA24 MCASP1_ACLKX is not used for audio. The pin is just floating unless this "GESI"-board with an additional ethernet interface is connect. AA24 is used as as MCASP1_ACLKX.RGMII1_RD0 in this case. See arch/arm64/boot/dts/ti/k3-j721s2-evm-gesi-exp-board.dtso Also the AA24 pin needs to be configured as HPD pin (muxmode 3) otherwise the mhdp firmware will not turn on the bridge. Dominik > When 'no-hpd' is set, DRM_BRIDGE_OP_HPD is omitted so the framework > falls back to polling .detect() every ~10 seconds. Monitor presence > is > determined via AUX DPCD reads instead of firmware HPD status > registers. > The .detect() callback drives cdns_mhdp_update_link_status() on each > poll to keep mhdp->plugged current. At attach time, the driver waits > for firmware to be ready before performing the initial AUX poll since > no interrupt will trigger it. > > Changes since v4: > - Corrected the dt-binding Subject > > Link to v4: > https://lore.kernel.org/all/[email protected]/ > > Rahul T R (2): > dt-bindings: display: bridge: cdns,mhdp8546: Add no-hpd property to > the cadence bridge > drm: bridge: cdns-mhdp8546: Add no-hpd property > > .../display/bridge/cdns,mhdp8546.yaml | 17 ++++++ > .../drm/bridge/cadence/cdns-mhdp8546-core.c | 58 ++++++++++++++++- > -- > .../drm/bridge/cadence/cdns-mhdp8546-core.h | 1 + > 3 files changed, 69 insertions(+), 7 deletions(-) >
