linux-kernel - Re: [PATCH] Revert "arm64: dma: Drop cache invalidation from arch_dma_prep

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Message-ID: <Y4joR2sQMMjIt+yE@arm.com>
Date:   Thu, 1 Dec 2022 17:45:43 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Thorsten Leemhuis <regressions@...mhuis.info>
Cc:     Sibi Sankar <quic_sibis@...cinc.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>, amit.pundir@...aro.org,
        andersson@...nel.org, sumit.semwal@...aro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "arm64: dma: Drop cache invalidation from
 arch_dma_prep_coherent()"

On Thu, Dec 01, 2022 at 10:29:39AM +0100, Thorsten Leemhuis wrote:
> Has any progress been made to fix this regression? It afaics is not a
> release critical issue, but well, it still would be nice to get this
> fixed before 6.1 is released.

The only (nearly) risk-free "fix" for 6.1 would be to revert the commit
that exposed the driver bug. It doesn't fix the actual bug, it only
makes it less likely to happen.

I like the original commit removing the cache invalidation as it shows
drivers not behaving properly but, as a workaround, we could add a
command line option to force back the old behaviour (defaulting to the
new one) until the driver is fixed.

-- 
Catalin