linux-kernel - Re: [PATCH] iommu/amd: Fix loop timeout issue in iommu_ga_log

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Date:   Fri, 4 Feb 2022 12:34:38 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     John Garry <john.garry@...wei.com>
Cc:     iommu@...ts.linux-foundation.org, Joerg Roedel <jroedel@...e.de>,
        linux-kernel@...r.kernel.org, Maxim Levitsky <mlevitsk@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH] iommu/amd: Fix loop timeout issue in
 iommu_ga_log_enable()

On Mon, Jan 31, 2022 at 05:06:03PM +0000, John Garry wrote:
> > diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
> > index dc338acf3338..d2e09d53851f 100644
> > --- a/drivers/iommu/amd/init.c
> > +++ b/drivers/iommu/amd/init.c
> > @@ -834,6 +834,7 @@ static int iommu_ga_log_enable(struct amd_iommu *iommu)
> >   		status = readl(iommu->mmio_base + MMIO_STATUS_OFFSET);
> >   		if (status & (MMIO_STATUS_GALOG_RUN_MASK))
> >   			break;
> > +		udelay(1);
> 
> Maybe readl_relaxed_poll_timeout_atomic() could be used instead

I sent another version of this patch which uses
readl_poll_timeout_atomic(), but it didn't fix the issue. I take this
approach for now and leave using the helper as a future improvement.

Thanks,

	Joerg