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

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Message-ID: <85607806-b888-2d5e-67a4-e9d63ebd1976@arm.com>
Date:   Wed, 22 Mar 2023 09:02:41 +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 21/03/2023 14:38, Jason Gunthorpe wrote:
> On Wed, Mar 15, 2023 at 04:41:52PM +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).
>>
>> Fixes: c1fe9119ee70 ("iommu: Add set_platform_dma_ops callbacks")
>> Signed-off-by: Steven Price <steven.price@....com>
>> ---
>> This fixes a splat I was seeing on a Firefly-RK3288, more details here:
>> https://lore.kernel.org/all/26a5d1b8-40b3-b1e4-bc85-740409c26838@arm.com/
> 
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Thanks for the review.

> Do you know what state the iommu is left in after
> rk_iommu_detach_device()? Ie is it blocking DMA or doing identity or
> something else?

To be honest I really don't know for sure. But from my small
understanding of the code: rk_iommu_detach_device() ends up in
rk_iommu_disable_paging() which appears to switch to identity mode
("Disable memory translation").

But I don't actually have any familiarity with the hardware block, so I
might be missing something.

Steve