Re: [PATCH RFC 51/51] ARM: 7805/1: mm: change max*pfn to include the physical offset of memory

Rob Herring
2013-08-06T03:15:14Z

On Thu, Aug 1, 2013 at 5:25 PM, Santosh Shilimkar
<santosh.shilimkar@ti.com> wrote:
> Most of the kernel code assumes that max*pfn is maximum pfns because
> the physical start of memory is expected to be PFN0. Since this
> assumption is not true on ARM architectures, the meaning of max*pfn
> is number of memory pages. This is done to keep drivers happy which
> are making use of of these variable to calculate the dma bounce limit
> using dma_mask.
>
> Now since we have a architecture override possibility for DMAable
> maximum pfns, lets make meaning of max*pfns as maximum pnfs on ARM
> as well.
>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> ---
> arch/arm/include/asm/dma-mapping.h | 8 ++++++++
> arch/arm/mm/init.c | 10 ++++------
> 2 files changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> index 5b579b9..863cd84 100644
> --- a/arch/arm/include/asm/dma-mapping.h
> +++ b/arch/arm/include/asm/dma-mapping.h
> @@ -64,6 +64,7 @@ static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
> {
> return (dma_addr_t)__virt_to_bus((unsigned long)(addr));
> }
> +
> #else
> static inline dma_addr_t pfn_to_dma(struct device *dev, unsigned long pfn)
> {
> @@ -86,6 +87,13 @@ static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
> }
> #endif
>
> +/* The ARM override for dma_max_pfn() */
> +static inline unsigned long dma_max_pfn(struct device *dev)
> +{
> + return PHYS_PFN_OFFSET + dma_to_pfn(dev, *dev->dma_mask);

Do we need to handle dev == NULL case?

Rob