Hi Magnus,
Thank you for the patch.
On Thursday 14 January 2016 18:59:33 Magnus Damm wrote:
> From: Magnus Damm <damm+renesas@xxxxxxxxxxxxx>
>
> Update the rcar-dmac driver to rework comments and variable names
> related to lowmem and highmem.
>
> Terminology such as highmem and lowmem are commonly used for Linux
> kernel memory managment. Highmem in particular is about handling more
> physical memory than can fit into the kernel virtual address space.
>
> Highmem and lowmem are related to but not equivalent to the 40-bit
> address limitation that is the real issue the rcar-dmac driver has to
> deal with. For instance, with 1 GiB of RAM highmem is usually needed
> on a 32-bit architecture, but a 32-bit address is still enough.
>
> 64-bit architectures tend to not use highmem since the virtual
> address space is more than enough for loads of lowmem. 32-bit
> architectures may still need highmem to access all memory.
>
> The rcar-dmac driver and the DMA device needs to handle the 40-bit
> limitation on both 64-bit and 32-bit architectures.
>
> This patch renames the highmem variable to fourty_bit_required to
> avoid confusion. And the comment gets updated as well.
>
> Signed-off-by: Magnus Damm <damm+renesas@xxxxxxxxxxxxx>
> ---
>
> drivers/dma/sh/rcar-dmac.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> --- 0001/drivers/dma/sh/rcar-dmac.c
> +++ work/drivers/dma/sh/rcar-dmac.c 2016-01-14 18:35:23.780513000 +0900
> @@ -889,7 +889,7 @@ rcar_dmac_chan_prep_sg(struct rcar_dmac_
> unsigned int nchunks = 0;
> unsigned int max_chunk_size;
> unsigned int full_size = 0;
> - bool highmem = false;
> + bool fourty_bit_required = false;
s/fourty_bit_required/fourty_bits_required/ ? Or, as the variable name seems a
bit long, need_40bits ?
> unsigned int i;
>
> desc = rcar_dmac_desc_get(chan);
> @@ -935,7 +935,7 @@ rcar_dmac_chan_prep_sg(struct rcar_dmac_
> * hardware descriptor lists.
> */
> if (dev_addr >> 32 || mem_addr >> 32)
> - highmem = true;
> + fourty_bit_required = true;
> #endif
>
> chunk = rcar_dmac_xfer_chunk_get(chan);
> @@ -977,13 +977,13 @@ rcar_dmac_chan_prep_sg(struct rcar_dmac_
> * Use hardware descriptor lists if possible when more than one chunk
> * needs to be transferred (otherwise they don't make much sense).
> *
> - * The highmem check currently covers the whole transfer. As an
> - * optimization we could use descriptor lists for consecutive lowmem
> - * chunks and direct manual mode for highmem chunks. Whether the
> + * The 40-bit address check currently covers the whole transfer. As an
> + * optimization we could use descriptor lists for consecutive 32-bit
> + * chunks and direct manual mode for 40-bit chunks. Whether the
> * performance improvement would be significant enough compared to the
> * additional complexity remains to be investigated.
> */
> - desc->hwdescs.use = !highmem && nchunks > 1;
> + desc->hwdescs.use = !fourty_bit_required && nchunks > 1;
> if (desc->hwdescs.use) {
> if (rcar_dmac_fill_hwdesc(chan, desc) < 0)
> desc->hwdescs.use = false;
--
Regards,
Laurent Pinchart
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