Re: [PATCH v9 18/38] phy: rockchip: usbdp: Drop DP HPD handling

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Incomplete cleanup of DP HPD logic leaves a dangerous register write in the probe path, violating power domain constraints and risking a bus hang (SError).
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Note: The format of this report has been altered to a free-form summary due
to restrictions on quoting the original patch code.

Commit: 985925db83ee1c14865f1eaca6f60b9245941678
Author: Sebastian Reichel <sebastian.reichel@collabora.com>
Subject: phy: rockchip: usbdp: Drop DP HPD handling

This commit drops the HPD handling logic from the USBDP PHY driver. The
commit message notes that the registers involved require the display
controller power domain to be enabled, and that HPD should be handled
by the displayport controller itself.

[Severity: High]

This is a pre-existing issue, but it appears the cleanup of the DP HPD logic
might be incomplete, leaving a potentially dangerous register write in the
probe path.

In rk_udphy_get_initial_status() in drivers/phy/rockchip/phy-rockchip-usbdp.c,
there is a check to see if the DP PHY was pre-enabled by the bootloader. If
it was, the driver writes false to the hpd_trigger register via
rk_udphy_grfreg_write() and then sleeps for 100ms.

Since the commit message explicitly acknowledges that these registers require
the display controller (VOP) power domain to be enabled, does this write
violate those power domain constraints? 

If the kernel disables the VOP power domain before this driver probes (for
example, due to asynchronous probing and the display driver suspending or
resetting its PM domain), could this write to hpd_trigger cause an
asynchronous abort (SError) and a subsequent kernel panic during boot?

Would it make sense to remove this remaining HPD trigger write in the initial
status check as well, to fully decouple the PHY driver from the display
controller power domain?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260702-rockchip-usbdp-cleanup-v9-0-e31efbb62d2e@collabora.com?part=18