[PATCH v5 0/2] Add no-hpd property to the cadence bridge
From: Yashas D <hidden>
Date: 2026-07-28 12:45:23
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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. 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/20260630102610.1849902-1-y-d@ti.com/ (local) 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(-) -- 2.34.1