Since patchset "arm64: Default to 32-bit wide ZONE_DMA", ZONE_DMA's
size is fine-tuned. In the absence of addressing limited masters,
ZONE_DMA will span the whole 32-bit address space, otherwise, in
the case of the Raspberry Pi 4, it'll only span the 30-bit address
space. Update the comments.
Signed-off-by: Chen Zhou <[email protected]>
---
arch/arm64/mm/init.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 75addb36354a..7b9809e39927 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -53,10 +53,11 @@ s64 memstart_addr __ro_after_init = -1;
EXPORT_SYMBOL(memstart_addr);
/*
- * We create both ZONE_DMA and ZONE_DMA32. ZONE_DMA covers the first 1G of
- * memory as some devices, namely the Raspberry Pi 4, have peripherals with
- * this limited view of the memory. ZONE_DMA32 will cover the rest of the 32
- * bit addressable memory area.
+ * We create both ZONE_DMA and ZONE_DMA32. ZONE_DMA's size is fine-tuned.
+ * In the absence of addressing limited masters, ZONE_DMA will span the
+ * whole 32-bit address space, otherwise, in the case of the Raspberry Pi 4,
+ * it'll only span the 30-bit address space. ZONE_DMA32 will cover the rest
+ * of the 32 bit addressable memory area.
*/
phys_addr_t arm64_dma_phys_limit __ro_after_init;
static phys_addr_t arm64_dma32_phys_limit __ro_after_init;
--
2.20.1
On Sat, 2020-12-26 at 11:35 +0800, Chen Zhou wrote:
> Since patchset "arm64: Default to 32-bit wide ZONE_DMA", ZONE_DMA's
> size is fine-tuned. In the absence of addressing limited masters,
> ZONE_DMA will span the whole 32-bit address space, otherwise, in
> the case of the Raspberry Pi 4, it'll only span the 30-bit address
> space. Update the comments.
>
> Signed-off-by: Chen Zhou <[email protected]>
> ---
Reviewed-by: Nicolas Saenz Julienne <[email protected]>
> arch/arm64/mm/init.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 75addb36354a..7b9809e39927 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -53,10 +53,11 @@ s64 memstart_addr __ro_after_init = -1;
> EXPORT_SYMBOL(memstart_addr);
>
>
> /*
> - * We create both ZONE_DMA and ZONE_DMA32. ZONE_DMA covers the first 1G of
> - * memory as some devices, namely the Raspberry Pi 4, have peripherals with
> - * this limited view of the memory. ZONE_DMA32 will cover the rest of the 32
> - * bit addressable memory area.
> + * We create both ZONE_DMA and ZONE_DMA32. ZONE_DMA's size is fine-tuned.
> + * In the absence of addressing limited masters, ZONE_DMA will span the
> + * whole 32-bit address space, otherwise, in the case of the Raspberry Pi 4,
> + * it'll only span the 30-bit address space. ZONE_DMA32 will cover the rest
> + * of the 32 bit addressable memory area.
> */
> phys_addr_t arm64_dma_phys_limit __ro_after_init;
> static phys_addr_t arm64_dma32_phys_limit __ro_after_init;