On 6/17/24 4:10 AM, Andre Przywara wrote:
> The Allwinner IOMMU is a strict 32-bit device, with its input addresses,
> the page table root pointer as well as both level's page tables and also
> the target addresses all required to be below 4GB.
> The Allwinner H6 SoC only supports 32-bit worth of physical addresses
> anyway, so this isn't a problem so far, but the H616 and later SoCs extend
> the PA space beyond 32 bit to accommodate more DRAM.
> To make sure we stay within the 32-bit PA range required by the IOMMU,
> force the memory for the page tables to come from below 4GB. by using
> allocations with the DMA32 flag.
> Also reject any attempt to map target addresses beyond 4GB, and print a
> warning to give users a hint while this fails.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
> drivers/iommu/sun50i-iommu.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/sun50i-iommu.c b/drivers/iommu/sun50i-iommu.c
> index dd3f07384624c..20a07f829085d 100644
> --- a/drivers/iommu/sun50i-iommu.c
> +++ b/drivers/iommu/sun50i-iommu.c
> @@ -602,6 +602,14 @@ static int sun50i_iommu_map(struct iommu_domain *domain, unsigned long iova,
> u32 *page_table, *pte_addr;
> int ret = 0;
>
> + /* the IOMMU can only handle 32-bit addresses, both input and output */
> + if ((uint64_t)paddr >> 32) {
> + ret = -EINVAL;
> + dev_warn_once(iommu->dev,
> + "attempt to map address beyond 4GB\n");
A133 uses the same IOMMU block and works fine when claimed by the display engine under 1GB
RAM. When used with 4GB,
root@helper-board-a133:~# head /proc/meminfo
MemTotal: 4021212 kB
root@helper-board-a133:~# dmesg | grep -i -e drm -e iommu
[ 0.465613] iommu: Default domain type: Translated
[ 0.470892] iommu: DMA domain TLB invalidation policy: strict mode
[ 0.914097] sun8i-mixer 6100000.mixer: Adding to iommu group 0
[ 1.092400] sun4i-drm display-engine: Adding to iommu group 0
[ 1.100044] sun4i-drm display-engine: bound 6100000.mixer (ops 0xffff800080b05dc0)
[ 1.108399] sun4i-drm display-engine: bound 6510000.tcon-top (ops 0xffff800080b0a628)
[ 1.116694] sun4i-drm display-engine: bound 6511000.lcd-controller (ops 0xffff800080b04220)
[ 1.126415] [drm] Initialized sun4i-drm 1.0.0 for display-engine on minor 0
[ 1.135110] sun50i-iommu 30f0000.iommu: attempt to map address beyond 4GB
[ 1.142559] sun4i-drm display-engine: [drm] *ERROR* fbdev-dma: Failed to setup generic emulation (ret=-12)
[ 1.154210] sun4i-drm display-engine: [drm] *ERROR* fbdev-dma: Failed to setup generic emulation (ret=-12)
allocation fails. Limiting the memory mem=2G to the kernel works.
Thanks,
Parthiban
> + goto out;
> + }
> +
> page_table = sun50i_dte_get_page_table(sun50i_domain, iova, gfp);
> if (IS_ERR(page_table)) {
> ret = PTR_ERR(page_table);
> @@ -682,7 +690,8 @@ sun50i_iommu_domain_alloc_paging(struct device *dev)
> if (!sun50i_domain)
> return NULL;
>
> - sun50i_domain->dt = iommu_alloc_pages(GFP_KERNEL, get_order(DT_SIZE));
> + sun50i_domain->dt = iommu_alloc_pages(GFP_KERNEL | GFP_DMA32,
> + get_order(DT_SIZE));
> if (!sun50i_domain->dt)
> goto err_free_domain;
>
> @@ -997,7 +1006,7 @@ static int sun50i_iommu_probe(struct platform_device *pdev)
>
> iommu->pt_pool = kmem_cache_create(dev_name(&pdev->dev),
> PT_SIZE, PT_SIZE,
> - SLAB_HWCACHE_ALIGN,
> + SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA32,
> NULL);
> if (!iommu->pt_pool)
> return -ENOMEM;
