diff mbox series

[1/2] arm64: mm: update the comments about ZONE_DMA

Message ID 20201226033557.116251-2-chenzhou10@huawei.com (mailing list archive)
State New, archived
Headers show
Series arm64: mm: fix kdump broken with ZONE_DMA reintroduced | expand

Commit Message

chenzhou Dec. 26, 2020, 3:35 a.m. UTC
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 <chenzhou10@huawei.com>
---
 arch/arm64/mm/init.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Comments

Nicolas Saenz Julienne Dec. 26, 2020, 10:35 a.m. UTC | #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 <chenzhou10@huawei.com>
> ---

Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>

>  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;
diff mbox series

Patch

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;