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

Yong Wu
2021-01-19T11:39:42Z

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@kernel.org>
> >>> CC: Frank Rowand <frowand.list@gmail.com>
> >>> Signed-off-by: Yong Wu <yong.wu@mediatek.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@kernel.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:

--- 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 */
- 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) {
+ 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.

>
> 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
> >>>
> >
> > _______________________________________________
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> > iommu@lists.linux-foundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/iommu
> >