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

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Date:   Tue, 19 Jan 2021 10:37:25 +0100
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     Yong Wu <yong.wu@...iatek.com>
Cc:     Robin Murphy <robin.murphy@....com>, Rob Herring <robh@...nel.org>,
        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
Subject: Re: [PATCH v6 06/33] of/device: Move dma_range_map before
 of_iommu_configure

Hi,

On Tue 19 Jan 21, 17:20, Yong Wu wrote:
> On Mon, 2021-01-18 at 15:49 +0000, Robin Murphy wrote:
> > 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.
> 
> Thanks this info. Following your suggestion, Move this into the "if (!
> ret)". Then it is like this:

Thanks for preparing the change :)

> 
> --- a/drivers/of/device.c
> +++ b/drivers/of/device.c
> @@ -163,8 +163,10 @@ int of_dma_configure_id(struct device *dev, struct
> device_node *np,
>  	dev->coherent_dma_mask &= mask;
>  	*dev->dma_mask &= mask;
>  	/* ...but only set bus limit if we found valid dma-ranges earlier */

Maybe the comment would need some update too, like:
/* ...but only set bus limit and map if we found valid dma-ranges earlier */

> -	if (!ret)
> +	if (!ret) {
>  		dev->bus_dma_limit = end;
> +		dev->dma_range_map = map;
> +	}
>  
>  	coherent = of_dma_is_coherent(np);
>  	dev_dbg(dev, "device is%sdma coherent\n",
> @@ -172,6 +174,8 @@ int of_dma_configure_id(struct device *dev, struct
> device_node *np,
>  
>  	iommu = of_iommu_configure(dev, np, id);
>  	if (PTR_ERR(iommu) == -EPROBE_DEFER) {

And maybe one here, something like:
/* don't touch range map if it wasn't set from a valid dma-ranges */

> +		if (!ret)
> +			dev->dma_range_map = NULL;
>  		kfree(map);
>  		return -EPROBE_DEFER;
>  	}
> @@ -181,7 +185,6 @@ 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);
> 
> 
> If this is ok, I will send this as a independent patch.

With the suggested changes, this looks good to me!

Thanks,

Paul

> > 
> > 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
> > > 
> 

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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