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

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Message-ID: <bee3e168-3fc3-89e8-6b10-a830f052cf55@arm.com>
Date:   Wed, 22 Mar 2023 16:04:25 +0000
From:   Steven Price <steven.price@....com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Heiko Stuebner <heiko@...ech.de>, Joerg Roedel <joro@...tes.org>,
        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,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: Re: [PATCH] iommu/rockchip: Add missing set_platform_dma_ops callback

On 22/03/2023 15:16, Jason Gunthorpe wrote:
> On Wed, Mar 22, 2023 at 03:08:41PM +0000, Steven Price wrote:
>> @@ -1035,8 +1055,9 @@ static int rk_iommu_attach_device(struct iommu_domain *domain,
>>  	if (iommu->domain == domain)
>>  		return 0;
>>  
>> -	if (iommu->domain)
>> -		rk_iommu_detach_device(iommu->domain, dev);
>> +	ret = rk_iommu_identity_attach(&rk_identity_domain, dev);
>> +	if (ret)
>> +		return ret;
> 
>>  
>>  	iommu->domain = domain;
>>  
>> @@ -1049,8 +1070,6 @@ static int rk_iommu_attach_device(struct iommu_domain *domain,
>>  		return 0;
>>  
>>  	ret = rk_iommu_enable(iommu);
>> -	if (ret)
>> -		rk_iommu_detach_device(iommu->domain, dev);
> 
> I think this still needs error handling, it should put it back to the
> identity domain and return an error code if it fails to attach to the
> requested domain.

What confused me here is that there's already a call to
rk_iommu_identity_attach() just above. But I can obviously add a...

       if (ret)
               rk_iommu_identity_attach(&rk_identity_domain, dev);

... in here. But I don't know how to handle an error from
rk_iommu_identity_attach() at this point. Does it need handling - is a
WARN_ON sufficient?

> It should also initlaize iommu->domain to the identity domain when the
> iommu struct is allocated. The iommu->domain should never be
> NULL. identity domain means the IOMMU is turned off which was
> previously called "detached".

I presume you mean in rk_iommu_probe()?

> Otherwise it looks like I would expect, thanks

Ok, I'll give it a spin with the above changes and post a v2 of this patch.

Thanks,

Steve