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

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Message-ID: <8fda817c-98e7-1988-325d-52d09f3e61a8@linux.intel.com>
Date:   Fri, 24 Mar 2023 21:16:24 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Steven Price <steven.price@....com>,
        Heiko Stuebner <heiko@...ech.de>,
        Joerg Roedel <joro@...tes.org>, Jason Gunthorpe <jgg@...pe.ca>
Cc:     baolu.lu@...ux.intel.com, 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 2023/3/24 19:11, 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
> @@ -124,6 +124,7 @@ struct rk_iommudata {
>   
>   static struct device *dma_dev;
>   static const struct rk_iommu_ops *rk_ops;
> +static struct iommu_domain rk_identity_domain;
>   
>   static inline void rk_table_flush(struct rk_iommu_domain *dom, dma_addr_t dma,
>   				  unsigned int count)
> @@ -980,26 +981,27 @@ static int rk_iommu_enable(struct rk_iommu *iommu)
>   	return ret;
>   }
>   
> -static void rk_iommu_detach_device(struct iommu_domain *domain,
> -				   struct device *dev)
> +static int rk_iommu_identity_attach(struct iommu_domain *identity_domain,
> +				    struct device *dev)
>   {
>   	struct rk_iommu *iommu;
> -	struct rk_iommu_domain *rk_domain = to_rk_domain(domain);
> +	struct rk_iommu_domain *rk_domain;
>   	unsigned long flags;
>   	int ret;
>   
>   	/* Allow 'virtual devices' (eg drm) to detach from domain */
>   	iommu = rk_iommu_from_dev(dev);
>   	if (!iommu)
> -		return;
> +		return -ENODEV;
> +
> +	rk_domain = to_rk_domain(iommu->domain);
>   
>   	dev_dbg(dev, "Detaching from iommu domain\n");
>   
> -	/* iommu already detached */
> -	if (iommu->domain != domain)
> -		return;
> +	if (iommu->domain == identity_domain)
> +		return 0;
>   
> -	iommu->domain = NULL;
> +	iommu->domain = identity_domain;

Where did identity_domain come from? Is it rk_identity_domain?

Best regards,
baolu