On 23.04.2018 09:57, Thierry Reding wrote:
> From: Thierry Reding <treding@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> ---
Reviewed-by: Dmitry Osipenko <digetx@xxxxxxxxx>
Tested-by: Dmitry Osipenko <digetx@xxxxxxxxx>
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?
> drivers/gpu/drm/tegra/drm.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
> index 4a696fa274a3..0540b0741df6 100644
> --- a/drivers/gpu/drm/tegra/drm.c
> +++ b/drivers/gpu/drm/tegra/drm.c
> @@ -115,6 +115,10 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
> goto free;
> }
>
> + err = iova_cache_get();
> + if (err < 0)
> + goto domain;
> +
Host1x also uses the alloc_iova(), though this allocation is actually invoked by
the DRM driver on requesting a channel. It is fine right now because DRM driver
is the only host1x user, but what about to add iova_cache_get() to the host1x
driver as well for consistency?
> geometry = &tegra->domain->geometry;
> gem_start = geometry->aperture_start;
> gem_end = geometry->aperture_end - CARVEOUT_SZ;
> @@ -205,11 +209,12 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
> tegra_drm_fb_free(drm);
> config:
> drm_mode_config_cleanup(drm);
> -
> +domain:
> if (tegra->domain) {
> mutex_destroy(&tegra->mm_lock);
> drm_mm_takedown(&tegra->mm);
> put_iova_domain(&tegra->carveout.domain);
> + iova_cache_put();
> iommu_domain_free(tegra->domain);
> }
> free:
> @@ -236,6 +241,7 @@ static void tegra_drm_unload(struct drm_device *drm)
> mutex_destroy(&tegra->mm_lock);
> drm_mm_takedown(&tegra->mm);
> put_iova_domain(&tegra->carveout.domain);
> + iova_cache_put();
> iommu_domain_free(tegra->domain);
> }
>
>
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