Mike Rapoport <[email protected]> writes:
> From: Mike Rapoport <[email protected]>
>
> Some powerpc platforms (e.g. 85xx) limit DMA-able memory way below 4G. If a
> system has more physical memory than this limit, the swiotlb buffer is not
> addressable because it is allocated from memblock using top-down mode.
>
> Force memblock to bottom-up mode before calling swiotlb_init() to ensure
> that the swiotlb buffer is DMA-able.
>
> Link:
> https://lkml.kernel.org/r/[email protected]
This wasn't bisected, but I thought it was a regression. Do we know what
commit caused it?
Was it 25078dc1f74b ("powerpc: use mm zones more sensibly") ?
Or was that a red herring?
cheers
> Reported-by: Christian Zigotzky <[email protected]>
> Signed-off-by: Mike Rapoport <[email protected]>
> Cc: Benjamin Herrenschmidt <[email protected]>
> Cc: Christoph Hellwig <[email protected]>
> Cc: Darren Stevens <[email protected]>
> Cc: mad skateman <[email protected]>
> Cc: Michael Ellerman <[email protected]>
> Cc: Nicolas Saenz Julienne <[email protected]>
> Cc: Paul Mackerras <[email protected]>
> Cc: Robin Murphy <[email protected]>
> Cc: Rob Herring <[email protected]>
> ---
> arch/powerpc/mm/mem.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index be941d382c8d..14c2c53e3f9e 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -260,6 +260,14 @@ void __init mem_init(void)
> BUILD_BUG_ON(MMU_PAGE_COUNT > 16);
>
> #ifdef CONFIG_SWIOTLB
> + /*
> + * Some platforms (e.g. 85xx) limit DMA-able memory way below
> + * 4G. We force memblock to bottom-up mode to ensure that the
> + * memory allocated in swiotlb_init() is DMA-able.
> + * As it's the last memblock allocation, no need to reset it
> + * back to to-down.
> + */
> + memblock_set_bottom_up(true);
> swiotlb_init(0);
> #endif
>
> --
> 2.24.0
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