On Mon, Nov 9, 2015 at 3:39 AM, Liu Jason <Hui.Liu@xxxxxxxxxxxxx> wrote:
> There is an alignment mismatch issue between the of_reserved_mem and the CMA setup requirement.
>
> The alignment in Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
>
>
> alignment (optional) - length based on parent's #size-cells
> - Address boundary for alignment of allocation.
>
>
> But this is not exactly match the CMA setup requirement if the alignment not set or set it not correctly.
>
> The of_reserved_mem will get the alignment from the DTS and pass it to __memblock_alloc_base to
> do the memory block allocation. If no alignment property in the DTS, the align will be SMP_CACHE_BYTES
IMO, any alignment requirement in the DTB should reflect h/w alignment
requirements. We can't know what alignment the OS wants. So if the OS
needs to further increase the alignment, it should adjust the
alignment.
>
> BUT, The CMA setup require the alignment as the following in the code:
>
> align = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order)
>
> static int __init rmem_cma_setup(struct reserved_mem *rmem)
> {
> phys_addr_t align = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
> phys_addr_t mask = align - 1;
> unsigned long node = rmem->fdt_node;
> struct cma *cma;
> int err;
>
> if (!of_get_flat_dt_prop(node, "reusable", NULL) ||
> of_get_flat_dt_prop(node, "no-map", NULL))
> return -EINVAL;
>
> if ((rmem->base & mask) || (rmem->size & mask)) {
> pr_err("Reserved memory: incorrect alignment of CMA region\n");
> return -EINVAL;
> }
> <snip>
> }
>
> So, there is very likely that the alignment mismatch between the of_reserved_mem and the CMA setup requirement.
> The sanity check in the rmem_cma_setup will fail and CMA not get set up in the end, this is not expected for CMA.
>
> In the test, there will be following err log when this mismatch happen.
>
> Reserved memory: incorrect alignment of CMA region.
>
> The following patch to fix this issue, any comments?
>
> =======================================================================================
>
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index 62f467b..a20d4d3 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -124,6 +124,15 @@ static int __init __reserved_mem_alloc_size(unsigned long node,
> align = dt_mem_next_cell(dt_root_addr_cells, &prop);
> }
>
> + if (of_flat_dt_is_compatible(node,"shared-dma-pool")) {
> + phys_addr_t align_required = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
> + if (!align || align != ALIGN(align, align_required)) {
> + pr_warn("Reserved memory: the alignment not set up correctly in '%s' node."
> + "change from %pa to %pa \n", uname, &align, &align_required);
> + align = align_required;
> + }
> + }
You simply need the max required from the DT (which could be more) or
CMA, so this can be simplified to:
align = max(align, PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
I don't think you should warn here either.
Rob
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