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Currently, downstream carries a commit that suppresses all but the first MMU error. While this avoids excessive logging, MMU error messages are often valuable for developers during debugging. At the moment, getting this information requires rebuilding the kernel with that commit reverted.

This PR proposes adding a new module parameter (downstream-only) to allow MMU error logging to be enabled on demand, avoiding the need to recompile the kernel.

As an alternative, we could simply revert the commit “drm/v3d: Suppress all but the first MMU error”, since MMU errors are no longer as frequent as they once were.

I'd appreciate to hear your thoughts about the preferred approach.

@pelwell
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pelwell commented Jan 9, 2026

I'm happy with a module parameter to enable the error logging, but not at the expense of losing even the first error if the parameter is disabled. I would lose the reversion, and make the logging condition !logged_error || debug_mmu.

MMU error messages are useful to help developers quickly identify
issues in userspace graphics drivers, but always printing them can
swamp the kernel log.

Add a module parameter, ``debug_mmu``, to gate MMU error logging.
Logging is disabled by default and can be enabled when needed with
``v3d.debug_mmu=1``.

Signed-off-by: Maíra Canal <[email protected]>
@mairacanal mairacanal force-pushed the v3d/downstream/mmu-debug branch from e7e7b98 to 338154d Compare January 9, 2026 15:48
@mairacanal
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I'm happy with a module parameter to enable the error logging, but not at the expense of losing even the first error if the parameter is disabled. I would lose the reversion, and make the logging condition !logged_error || debug_mmu.

I updated the branch with your suggestion. Thanks!

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2 participants