[PATCH] dmaengine: fsl-edma: fixup reg offset and hw S/G support in big-endian model
From: arnd@arndb.de (Arnd Bergmann)
Date: 2014-09-23 12:31:11
Also in:
lkml
On Tuesday 23 September 2014 17:15:19 Jingchang Lu wrote:
quoted hunk ↗ jump to hunk
@@ -459,20 +480,27 @@ static void fill_tcd_params(struct fsl_edma_engine *edma, u16 csr = 0; /* - * eDMA hardware SGs require the TCD parameters stored in memory - * the same endian as the eDMA module so that they can be loaded - * automatically by the engine + * eDMA hardware SGs requires the TCDs to be auto loaded + * in the same endian as the core whenver the eDAM engine's + * register endian. So we don't swap the value, waitting + * for fsl_set_tcd_params doing the swap. */
This makes no sense: how would the eDMA hardware know what endianess the CPU is using to write this data? Have you tried this running on the same hardware with both big-endian and little-endian kernels? Also, you access this as little-endian data unconditionally rather than cpu-endian as the comment suggests, maybe that is what you meant here?
- edma_writel(edma, src, &(tcd->saddr)); - edma_writel(edma, dst, &(tcd->daddr)); - edma_writew(edma, attr, &(tcd->attr)); - edma_writew(edma, EDMA_TCD_SOFF_SOFF(soff), &(tcd->soff)); - edma_writel(edma, EDMA_TCD_NBYTES_NBYTES(nbytes), &(tcd->nbytes)); - edma_writel(edma, EDMA_TCD_SLAST_SLAST(slast), &(tcd->slast)); - edma_writew(edma, EDMA_TCD_CITER_CITER(citer), &(tcd->citer)); - edma_writew(edma, EDMA_TCD_DOFF_DOFF(doff), &(tcd->doff)); - edma_writel(edma, EDMA_TCD_DLAST_SGA_DLAST_SGA(dlast_sga), &(tcd->dlast_sga)); - edma_writew(edma, EDMA_TCD_BITER_BITER(biter), &(tcd->biter)); + writel(src, &(tcd->saddr)); + writel(dst, &(tcd->daddr)); + + writew(attr, &(tcd->attr));
You seem to have another preexisting bug: The tcd pointer actually does not point to mmio registers here at all, but instead points to memory that has been returned from dma_pool_alloc. It is not valid to use writel() on such memory, that is only meant to work on real MMIO registers. You should use regular assignments to the registers here, e.g. tcd->saddr = cpu_to_le32(src); tcd->daddr = cpu_to_le32(dst); ... Arnd