linux-kernel - Re: [PATCH v2] iommu/rockchip: Add missing set_platform_dma

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Date:   Mon, 27 Mar 2023 15:35:04 +0100
From:   John Keeping <john@...anate.com>
To:     Steven Price <steven.price@....com>
Cc:     Heiko Stuebner <heiko@...ech.de>, Joerg Roedel <joro@...tes.org>,
        Jason Gunthorpe <jgg@...pe.ca>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v2] iommu/rockchip: Add missing set_platform_dma_ops
 callback

On Fri, Mar 24, 2023 at 11:11:27AM +0000, Steven Price wrote:
> Similar to exynos, we need a set_platform_dma_ops() callback for proper
> operation on ARM 32 bit after recent changes in the IOMMU framework
> (detach ops removal). But also the use of a NULL domain is confusing.
> 
> Rework the code to have a singleton rk_identity_domain which is assigned
> to domain when using an identity mapping rather than "detaching". This
> makes the code easier to reason about.
> 
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> Changes since v1[1]:
> 
>  * Reworked the code to avoid a NULL domain, instead a singleton
>    rk_identity_domain is used instead. The 'detach' language is no
>    longer used.
> 
> [1] https://lore.kernel.org/r/20230315164152.333251-1-steven.price%40arm.com
> 
>  drivers/iommu/rockchip-iommu.c | 50 ++++++++++++++++++++++++++--------
>  1 file changed, 39 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
> index f30db22ea5d7..437541004994 100644
> --- a/drivers/iommu/rockchip-iommu.c
> +++ b/drivers/iommu/rockchip-iommu.c
[snip]
> +static struct iommu_domain rk_identity_domain = {
> +	.type = IOMMU_DOMAIN_IDENTITY,
> +	.ops = &rk_identity_ops,
> +};
> +
> +#ifdef CONFIG_ARM

Is this #ifdef needed?  I can't see anything ARM-specific about this
function or .set_platform_dma_ops.

> +static void rk_iommu_set_platform_dma(struct device *dev)
> +{
> +	WARN_ON(rk_iommu_identity_attach(&rk_identity_domain, dev));
>  }
> +#endif

Not shown in the patch are the pm_runtime hooks.  Do they need to
change like this?

 static int __maybe_unused rk_iommu_suspend(struct device *dev)
 {
 	struct rk_iommu *iommu = dev_get_drvdata(dev);
 
-	if (!iommu->domain)
+	if (iommu->domain == &rk_identity_domain)
 		return 0;
 
 	rk_iommu_disable(iommu);
 	return 0;
 }
 
 static int __maybe_unused rk_iommu_resume(struct device *dev)
 {
 	struct rk_iommu *iommu = dev_get_drvdata(dev);
 
-	if (!iommu->domain)
+	if (iommu->domain == &rk_identity_domain)
 		return 0;
 
 	return rk_iommu_enable(iommu);
 }