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SubjectRe: [PATCH v3] dmaengine: xgene-dma: Fix sparse wannings and coccinelle warnings
Date
On Friday 17 April 2015 01:01:13 Rameshwar Prasad Sahu wrote:
> v3 changes:
> * Minor changes in length setting in DMA descriptor
>
> v2 changes:
> * Code cleanup
> * Changed way of setting DMA descriptors for big-endian
>
> This patch fixes compilation sparse warnings like incorrect type in assignment
> (different base types), cast to restricted __le64, symbol
> '__UNIQUE_ID_author__COUNTER__' has multiple initializers etc and
> coccinelle warnings (No need to set .owner here. The core will do it.)
>
> This patch is based on slave-dma / for-linus branch.
> (commit: 9f2fd0dfa594d857fbdaeda523ff7a46f16567f5 [26/28]
> dmaengine: Add support for APM X-Gene SoC DMA engine driver)
>
> Reported-by: kbuild test robot <fengguang.wu@intel.com>
> Signed-off-by: Rameshwar Prasad Sahu <rsahu@apm.com>

Looks good now,

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

There is one small enhancement that you could still do and I'll shut up after
that ;-)

>
> -static void *xgene_dma_lookup_ext8(u64 *desc, int idx)
> +static __le64 *xgene_dma_lookup_ext8(struct xgene_dma_desc_hw *desc, int idx)
> {
> - return (idx % 2) ? (desc + idx - 1) : (desc + idx + 1);
> + switch (idx) {
> + case 0:
> + return &desc->m1;
> + case 1:
> + return &desc->m0;
> + case 2:
> + return &desc->m3;
> + case 3:
> + return &desc->m2;
> + default:
> + pr_err("Invalid dma descriptor index\n");
> + }
> +
> + return NULL;
> }
>
...

> /* Set 1st to 5th source addresses */
> for (i = 0; i < src_cnt; i++) {
> len = *nbytes;
> - xgene_dma_set_src_buffer((i == 0) ? (desc1 + 8) :
> + xgene_dma_set_src_buffer((i == 0) ? &desc1->m1 :
> xgene_dma_lookup_ext8(desc2, i - 1),
> &len, &src[i]);
> - XGENE_DMA_DESC_MULTI_SET(desc1, scf[i], i);
> + desc1->m2 |= cpu_to_le64((scf[i] << ((i + 1) * 8)));
> }

If you just unroll this loop, you get code that is smaller and easier to
understand:

/* Set 1st to 5th source addresses */
xgene_dma_set_src_buffer(&desc1->m1, &len, &src[0]);
xgene_dma_set_src_buffer(&desc2->m0, &len, &src[1]);
xgene_dma_set_src_buffer(&desc2->m3, &len, &src[2]);
xgene_dma_set_src_buffer(&desc2->m2, &len, &src[3]);
desc1->m2 |= cpu_to_le64(scf[0] | scf[1] << 8 | scf[2] << 16 | scf[3] << 24);

Arnd


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