From: Sricharan R <sricharan@codeaurora.org>
To: Robin Murphy <robin.murphy@arm.com>,
Geert Uytterhoeven <geert@linux-m68k.org>
Cc: okaya@codeaurora.org,
"linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>,
Magnus Damm <magnus.damm@gmail.com>,
Will Deacon <will.deacon@arm.com>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
iommu@lists.linux-foundation.org,
linux-pci <linux-pci@vger.kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
tn@semihalf.com,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH V8 07/11] iommu: of: Handle IOMMU lookup failure with deferred probing or error
Date: Wed, 3 May 2017 16:43:05 +0530 [thread overview]
Message-ID: <9742498a-a415-6725-3aa0-b29089152383@codeaurora.org> (raw)
In-Reply-To: <26defadf-6380-4af4-6323-b51198376bc1@codeaurora.org>
Hi,
On 5/3/2017 3:54 PM, Sricharan R wrote:
> Hi Robin,
>
> On 5/3/2017 3:24 PM, Robin Murphy wrote:
>> Hi Geert,
>>
>> On 02/05/17 19:35, Geert Uytterhoeven wrote:
>>> Hi Sricharan,
>>>
>>> On Fri, Feb 3, 2017 at 4:48 PM, Sricharan R <sricharan@codeaurora.org> wrote:
>>>> From: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
>>>>
>>>> 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@samsung.com>
>>>> Signed-off-by: Laurent Pichart <laurent.pinchart+renesas@ideasonboard.com>
>>>> Signed-off-by: Sricharan R <sricharan@codeaurora.org>
>>>
>>> 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@codeaurora.org>
> 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@codeaurora.org>
> ---
> 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;
>
While same as the other 'status=disabled' patch [1], better not to
defer the probe itself in the case ?
[1] https://patchwork.kernel.org/patch/9681211/
Regards,
Sricharan
--
"QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
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next prev parent reply other threads:[~2017-05-03 11:13 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-03 15:48 [PATCH V8 00/11] IOMMU probe deferral support Sricharan R
2017-02-03 15:48 ` [PATCH V8 01/11] iommu/of: Refactor of_iommu_configure() for error handling Sricharan R
2017-03-08 18:58 ` Jean-Philippe Brucker
2017-03-08 19:28 ` Robin Murphy
2017-03-09 9:52 ` sricharan
2017-03-09 11:21 ` Robin Murphy
2017-02-03 15:48 ` [PATCH V8 02/11] iommu/of: Prepare for deferred IOMMU configuration Sricharan R
2017-02-03 15:48 ` [PATCH V8 03/11] of: dma: Move range size workaround to of_dma_get_range() Sricharan R
2017-02-03 15:48 ` [PATCH V8 04/11] of: dma: Make of_dma_deconfigure() public Sricharan R
2017-02-03 15:48 ` [PATCH V8 05/11] ACPI/IORT: Add function to check SMMUs drivers presence Sricharan R
2017-02-03 15:48 ` [PATCH V8 06/11] of/acpi: Configure dma operations at probe time for platform/amba/pci bus devices Sricharan R
2017-02-03 15:48 ` [PATCH V8 07/11] iommu: of: Handle IOMMU lookup failure with deferred probing or error Sricharan R
2017-05-02 18:35 ` Geert Uytterhoeven
2017-05-03 9:54 ` Robin Murphy
2017-05-03 10:24 ` Sricharan R
2017-05-03 11:13 ` Sricharan R [this message]
2017-05-05 13:23 ` Geert Uytterhoeven
2017-05-17 9:22 ` Magnus Damm
2017-05-17 10:28 ` Sricharan R
2017-05-15 14:22 ` Will Deacon
2017-05-16 2:26 ` sricharan
2017-05-15 20:37 ` Laurent Pinchart
2017-05-15 21:34 ` Laurent Pinchart
2017-05-16 2:23 ` sricharan
2017-05-16 7:17 ` Laurent Pinchart
2017-05-16 9:47 ` Sakari Ailus
2017-05-16 13:40 ` sricharan
2017-05-16 14:06 ` Laurent Pinchart
2017-05-16 14:04 ` Robin Murphy
2017-05-16 14:10 ` Laurent Pinchart
2017-05-16 14:29 ` sricharan
2017-05-16 14:46 ` Laurent Pinchart
2017-05-16 14:52 ` Robin Murphy
2017-02-03 15:48 ` [PATCH V8 08/11] drivers: acpi: " Sricharan R
2017-02-03 16:15 ` Sricharan
2017-02-03 17:39 ` Robin Murphy
2017-02-05 6:51 ` Sricharan
2017-02-03 15:48 ` [PATCH V8 09/11] arm64: dma-mapping: Remove the notifier trick to handle early setting of dma_ops Sricharan R
2017-02-03 15:48 ` [PATCH V8 10/11] iommu/arm-smmu: Clean up early-probing workarounds Sricharan R
2017-02-03 15:48 ` [PATCH V8 11/11] ACPI/IORT: Remove linker section for IORT entries probing Sricharan R
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