From e963adad3a5b56b9824691fbca82cbced83fbcac Mon Sep 17 00:00:00 2001 From: Jon Medhurst Date: Tue, 15 Apr 2014 17:18:15 +0100 Subject: [PATCH] dma: pl330: Align DMA memcpy operations to MFIFO width The algorithm used for programming the DMA Controller doesn't take into consideration the requirements of transfers that are not aligned to the bus width. Work around this by making sure we pick a bust size and length which ensures no bursts straddle an MFIFO entry. See "MFIFO Usage Overview" chapter in the the TRM for "CoreLink DMA Controller DMA-330", Revision r1p1. Signed-off-by: Jon Medhurst --- drivers/dma/pl330.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c index 2e147cb..56ad8e6 100644 --- a/drivers/dma/pl330.c +++ b/drivers/dma/pl330.c @@ -2759,8 +2759,13 @@ pl330_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dst, /* Select max possible burst size */ burst = pi->pcfg.data_bus_width / 8; + /* + * Make sure we use a burst size that aligns with all the memcpy + * parameters because our DMA programming algorithm doesn't cope with + * transfers which straddle an entry in the DMA device's MFIFO. + */ while (burst > 1) { - if (!(len % burst)) + if (!((src | dst | len) % burst)) break; burst /= 2; } @@ -2769,6 +2774,13 @@ pl330_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dst, while (burst != (1 << desc->rqcfg.brst_size)) desc->rqcfg.brst_size++; + /* + * If burst size is smaller than bus width then make sure we only + * transfer one at a time to avoid a burst stradling an MFIFO entry. + */ + if (desc->rqcfg.brst_size * 8 < pi->pcfg.data_bus_width) + desc->rqcfg.brst_len = 1; + desc->rqcfg.brst_len = get_burst_len(desc, len); desc->txd.flags = flags; -- 2.7.4