Subject: [PATCH 06/10] iommu: of: Handle IOMMU lookup failure with deferred probing or error

From: [email-masked] (Sricharan)
Date: Wed, 30 Nov 2016 16:57:33 +0530

Hi,

>Hi Sricharan and Robin,
>
>
>On 2016-11-30 01:22, Sricharan R wrote:
>> From: Laurent Pinchart <[email-masked]>
>>
>> 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.
>>
>> Signed-off-by: Laurent Pichart <[email-masked]>
>> Signed-off-by: Sricharan R <[email-masked]>
>> [rm: massive PCI hacks]
>> Signed-off-by: Robin Murphy <[email-masked]>
>> ---
>>   drivers/base/dma-mapping.c | 4 ++--
>>   drivers/iommu/dma-iommu.c  | 1 +
>>   drivers/iommu/of_iommu.c   | 5 +++--
>>   drivers/of/device.c        | 9 +++++++--
>>   drivers/pci/probe.c        | 6 ++++--
>>   include/linux/of_device.h  | 9 ++++++---
>>   include/linux/pci.h        | 4 ++--
>>   7 files changed, 25 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
>> index b2a5629..576fdfb 100644
>> --- a/drivers/base/dma-mapping.c
>> +++ b/drivers/base/dma-mapping.c
>> @@ -351,9 +351,9 @@ void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags)
>>   int dma_configure(struct device *dev)
>>   {
>>   	if (dev_is_pci(dev))
>> -		pci_dma_configure(dev);
>> +		return pci_dma_configure(dev);
>>   	else if (dev->of_node)
>> -		of_dma_configure(dev, dev->of_node);
>> +		return of_dma_configure(dev, dev->of_node);
>>   	return 0;
>>   }
>>
>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>> index c5ab866..d2a7a46 100644
>> --- a/drivers/iommu/dma-iommu.c
>> +++ b/drivers/iommu/dma-iommu.c
>> @@ -148,6 +148,7 @@ int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
>>   	base_pfn = max_t(unsigned long, 1, base >> order);
>>   	end_pfn = (base + size - 1) >> order;
>>
>> +	dev_info(dev, "0x%llx 0x%llx, 0x%llx 0x%llx, 0x%llx 0x%llx\n", base, size, domain->geometry.aperture_start, domain-
>>geometry.aperture_end,
>
>This causes a NULL pointer dereference if caller passes NULL device pointer.
>There is such caller in drivers/gpu/drm/exynos/exynos_drm_iommu.h.
>Trivial to fix as it looks like a leftover from developement or
>debugging stage.
>
My bad, i should have removed it before posting. Noticed this, but missed to remove it.
Will do so.

Regards,
 Sricharan