On Wed, 4 Dec 2019 13:56:33 +0100, Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> wrote:
> Raspberry Pi's firmware has a feature to select how much memory to
> reserve for its GPU called 'gpu_mem'. The possible values go from 16MB
> to 944MB, with a default of 64MB. This memory resides in the topmost
> part of the lower 1GB memory area and grows bigger expanding towards the
> begging of memory.
>
> It turns out that with low 'gpu_mem' values (16MB and 32MB) the size of
> the memory available to the system in the lower 1GB area can outgrow the
> interconnect's dma-range as its size was selected based on the maximum
> system memory available given the default gpu_mem configuration. This
> makes that memory slice unavailable for DMA. And may cause nasty kernel
> warnings if CMA happens to include it.
>
> Change soc's dma-ranges to really reflect it's HW limitation, which is
> being able to only DMA to the lower 1GB area.
>
> Fixes: 7dbe8c62ceeb ("ARM: dts: Add minimal Raspberry Pi 4 support")
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
> ---
Applied to devicetree/fixes, thanks!
--
Florian
