accel/amdxdna: Fix race where send ring appears full due to delayed head update

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[ Upstream commit 343f5683cf ]

The firmware sends a response and interrupts the driver before advancing
the mailbox send ring head pointer. As a result, the driver may observe
the response and attempt to send a new request before the firmware has
updated the head pointer. In this window, the send ring still appears
full, causing the driver to incorrectly fail the send operation.

This race can be triggered more easily in a multithreaded environment,
leading to unexpected and spurious "send ring full" failures.

To address this, poll the send ring head pointer for up to 100us before
returning a full-ring condition. This allows the firmware time to update
the head pointer.

Fixes: b87f920b93 ("accel/amdxdna: Support hardware mailbox")
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20251211045125.1724604-1-lizhi.hou@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Lizhi Hou 2025-12-10 20:51:25 -08:00 • committed by Greg Kroah-Hartman

parent 0b0d8ed13d

commit 5b295f0133

1 changed files with 16 additions and 11 deletions

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drivers/accel/amdxdna/amdxdna_mailbox.c

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