linux-kernel - Re: [PATCH v6 06/33] of/device: Move dma_range_map before of_iommu_configure

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Date:   Mon, 18 Jan 2021 15:49:06 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Yong Wu <yong.wu@...iatek.com>, Rob Herring <robh@...nel.org>
Cc:     youlin.pei@...iatek.com, devicetree@...r.kernel.org,
        Nicolas Boichat <drinkcat@...omium.org>,
        srv_heupstream@...iatek.com, chao.hao@...iatek.com,
        Will Deacon <will@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        linux-kernel@...r.kernel.org, Evan Green <evgreen@...omium.org>,
        Tomasz Figa <tfiga@...gle.com>,
        iommu@...ts.linux-foundation.org,
        linux-mediatek@...ts.infradead.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        anan.sun@...iatek.com, linux-arm-kernel@...ts.infradead.org,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Subject: Re: [PATCH v6 06/33] of/device: Move dma_range_map before
 of_iommu_configure

On 2021-01-15 05:30, Yong Wu wrote:
> On Thu, 2021-01-14 at 13:27 -0600, Rob Herring wrote:
>> On Mon, Jan 11, 2021 at 07:18:47PM +0800, Yong Wu wrote:
>>> "dev->dma_range_map" contains the devices' dma_ranges information,
>>> This patch moves dma_range_map before of_iommu_configure. The iommu
>>> driver may need to know the dma_address requirements of its iommu
>>> consumer devices.
>>>
>>> CC: Rob Herring <robh+dt@...nel.org>
>>> CC: Frank Rowand <frowand.list@...il.com>
>>> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
>>> ---
>>>   drivers/of/device.c | 3 ++-
>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/of/device.c b/drivers/of/device.c
>>> index aedfaaafd3e7..1d84636149df 100644
>>> --- a/drivers/of/device.c
>>> +++ b/drivers/of/device.c
>>> @@ -170,9 +170,11 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
>>>   	dev_dbg(dev, "device is%sdma coherent\n",
>>>   		coherent ? " " : " not ");
>>>   
>>> +	dev->dma_range_map = map;
>>>   	iommu = of_iommu_configure(dev, np, id);
>>>   	if (PTR_ERR(iommu) == -EPROBE_DEFER) {
>>>   		kfree(map);
>>> +		dev->dma_range_map = NULL;
>>
>> Not really going to matter, but you should probably clear dma_range_map
>> before what it points to is freed.
>>
>> With that,
>>
>> Reviewed-by: Rob Herring <robh@...nel.org>
> 
> Thanks for the review. I will move it before "kfree(map)" in next
> version.

Paul noticed that we already have a bug in assigning to this 
unconditionally[1] - I'd totally forgotten about this series when I 
theorised about IOMMU drivers wanting the information earlier, but 
sweeping my inbox now only goes to show I was right to think of it :)

We should really get something in as a fix independent of this series, 
taking both angles into account.

Robin.

[1] 
https://lore.kernel.org/linux-arm-kernel/5c7946f3-b56e-da00-a750-be097c7ceb32@arm.com/

>>
>>>   		return -EPROBE_DEFER;
>>>   	}
>>>   
>>> @@ -181,7 +183,6 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
>>>   
>>>   	arch_setup_dma_ops(dev, dma_start, size, iommu, coherent);
>>>   
>>> -	dev->dma_range_map = map;
>>>   	return 0;
>>>   }
>>>   EXPORT_SYMBOL_GPL(of_dma_configure_id);
>>> -- 
>>> 2.18.0
>>>
> 
> _______________________________________________
> iommu mailing list
> iommu@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
> 

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