Hi Will,
On 2017-05-15 19:52, Will Deacon wrote:
Hi Sricharan,
On Wed, May 03, 2017 at 03:54:59PM +0530, Sricharan R wrote:
On 5/3/2017 3:24 PM, Robin Murphy wrote:
> On 02/05/17 19:35, Geert Uytterhoeven wrote:
>> On Fri, Feb 3, 2017 at 4:48 PM, Sricharan R <sricharan@xxxxxxxxxxxxxx> wrote:
>>> From: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
>>>
>>> Failures to look up an IOMMU when parsing the DT iommus property need to
>>> be handled separately from the .of_xlate() failures to support deferred
>>> probing.
>>>
>>> The lack of a registered IOMMU can be caused by the lack of a driver for
>>> the IOMMU, the IOMMU device probe not having been performed yet, having
>>> been deferred, or having failed.
>>>
>>> The first case occurs when the device tree describes the bus master and
>>> IOMMU topology correctly but no device driver exists for the IOMMU yet
>>> or the device driver has not been compiled in. Return NULL, the caller
>>> will configure the device without an IOMMU.
>>>
>>> The second and third cases are handled by deferring the probe of the bus
>>> master device which will eventually get reprobed after the IOMMU.
>>>
>>> The last case is currently handled by deferring the probe of the bus
>>> master device as well. A mechanism to either configure the bus master
>>> device without an IOMMU or to fail the bus master device probe depending
>>> on whether the IOMMU is optional or mandatory would be a good
>>> enhancement.
>>>
>>> Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
>>> Signed-off-by: Laurent Pichart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
>>> Signed-off-by: Sricharan R <sricharan@xxxxxxxxxxxxxx>
>>
>> This patch broke Renesas R-Car Gen3 platforms in renesas-drivers.
>> As the IOMMU nodes in DT are not yet enabled, all devices having iommus
>> properties in DT now fail to probe.
>
> How exactly do they fail to probe? Per d7b0558230e4, if there are no ops
> registered then they should merely defer until we reach the point of
> giving up and ignoring the IOMMU. Is it just that you have no other
> late-probing drivers or post-init module loads to kick the deferred
> queue after that point? I did try to find a way to explicitly kick it
> from a suitably late initcall, but there didn't seem to be any obvious
> public interface - anyone have any suggestions?
>
> I think that's more of a general problem with the probe deferral
> mechanism itself (I've seen the same thing happen with some of the
> CoreSight stuff on Juno due to the number of inter-component
> dependencies) rather than any specific fault of this series.
>
I was thinking of an additional check like below to avoid the
situation ?
From 499b6e662f60f23740b8880882b0a16f16434501 Mon Sep 17 00:00:00 2001
From: Sricharan R <sricharan@xxxxxxxxxxxxxx>
Date: Wed, 3 May 2017 13:16:59 +0530
Subject: [PATCH] iommu: of: Fix check for returning EPROBE_DEFER
While returning EPROBE_DEFER for iommu masters
take in to account of iommu nodes that could be
marked in DT as 'status=disabled', in which case
simply return NULL and let the master's probe
continue rather than deferring.
Signed-off-by: Sricharan R <sricharan@xxxxxxxxxxxxxx>
---
drivers/iommu/of_iommu.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 9f44ee8..e6e9bec 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -118,6 +118,7 @@ static bool of_iommu_driver_present(struct
device_node *np)
ops = iommu_ops_from_fwnode(fwnode);
if ((ops && !ops->of_xlate) ||
+ !of_device_is_available(iommu_spec->np) ||
(!ops && !of_iommu_driver_present(iommu_spec->np)))
return NULL;
Without this patch, v4.12-rc1 hangs on my Juno waiting to mount the
root
filesystem. The problem is that the USB controller is behind an SMMU
which
is marked as 'status = "disabled"' in the devicetree. Whilst there was
a
separate thread with Ard about exactly what this means in terms of the
DMA
ops used by upstream devices, your patch above fixes the regression and
I think should go in regardless. The DMA ops issue will likely require
an additional DT binding anyway, to advertise the behaviour of the
IOMMU when it is disabled.
Tested-by: Will Deacon <will.deacon@xxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
Could you resend it as a proper patch, please?
Sure, will send this as a separate patch.
Regards,
Sricharan
