[PATCH 2/2] drm/tegra: Acquire a reference to the IOVA cache

[Dmitry Osipenko]

On 23.04.2018 11:41, Dmitry Osipenko wrote:
> On 23.04.2018 11:34, Dmitry Osipenko wrote:
>> On 23.04.2018 09:57, Thierry Reding wrote:
>>> From: Thierry Reding <treding at nvidia.com>
>>>
>>> The IOVA API uses a memory cache to allocate IOVA nodes from. To make
>>> sure that this cache is available, obtain a reference to it and release
>>> the reference when the cache is no longer needed.
>>>
>>> On 64-bit ARM this is hidden by the fact that the DMA mapping API gets
>>> that reference and never releases it. On 32-bit ARM, however, the DMA
>>> mapping API doesn't do that, so allocation of IOVA nodes fails.
>>>
>>> Signed-off-by: Thierry Reding <treding at nvidia.com>
>>> ---
>>
>> Reviewed-by: Dmitry Osipenko <digetx at gmail.com>
>> Tested-by: Dmitry Osipenko <digetx at gmail.com>
>>
>> CONFIG_TEGRA_IOMMU_SMMU is enabled in the default kernel configs and hence DRM
>> should fail to probe on t124 since 4.11. What about to add stable tag for v4.11+
>> here to unbreak stable kernels as well?
> 
> IOMMU node for host1x was added to t124 DT in kernel v4.14, so s/4.11/4.14/.

On the other hand nothing stops to use newer DT with older kernel.