From 9a1a34f3c8612864f18a71febc134957a03eca64 Mon Sep 17 00:00:00 2001 From: Niklas Cassel Date: Mon, 24 Oct 2016 15:29:15 +0200 Subject: [PATCH] dmaengine: nbpfaxi: add optional max-burst property for memory reads/writes Due to a hardware bug, reading memory (from the Accelerator Coherency Port) with a burst size equal to the maximum burst size allowed by the DMA hardware's buffer size will cause a hardware hang on the ARTPEC-6 SoC, where the only solution is a manual power cycle. On ARTPEC-6, this hardware bug does not trigger when writing memory (to the Accelerator Coherency Port) with a burst size equal to the maximum burst size allowed by the DMA hardware's buffer size. To avoid this hardware hang, introduce a new optional max-burst property for memory reads. For completeness, also introduce a max-burst property for memory writes. Signed-off-by: Niklas Cassel Acked-by: Rob Herring Signed-off-by: Vinod Koul --- .../devicetree/bindings/dma/nbpfaxi.txt | 8 ++++ drivers/dma/nbpfaxi.c | 38 +++++++++++++++++-- 2 files changed, 42 insertions(+), 4 deletions(-) diff --git a/Documentation/devicetree/bindings/dma/nbpfaxi.txt b/Documentation/devicetree/bindings/dma/nbpfaxi.txt index d5e2522b9ec1..d2e1e62e346a 100644 --- a/Documentation/devicetree/bindings/dma/nbpfaxi.txt +++ b/Documentation/devicetree/bindings/dma/nbpfaxi.txt @@ -23,6 +23,14 @@ Required properties #define NBPF_SLAVE_RQ_LEVEL 4 Optional properties: +- max-burst-mem-read: limit burst size for memory reads + (DMA_MEM_TO_MEM/DMA_MEM_TO_DEV) to this value, specified in bytes, rather + than using the maximum burst size allowed by the hardware's buffer size. +- max-burst-mem-write: limit burst size for memory writes + (DMA_DEV_TO_MEM/DMA_MEM_TO_MEM) to this value, specified in bytes, rather + than using the maximum burst size allowed by the hardware's buffer size. + If both max-burst-mem-read and max-burst-mem-write are set, DMA_MEM_TO_MEM + will use the lower value. You can use dma-channels and dma-requests as described in dma.txt, although they won't be used, this information is derived from the compatibility string. diff --git a/drivers/dma/nbpfaxi.c b/drivers/dma/nbpfaxi.c index 09de71519d37..3f45b9bdf201 100644 --- a/drivers/dma/nbpfaxi.c +++ b/drivers/dma/nbpfaxi.c @@ -225,6 +225,8 @@ struct nbpf_channel { struct nbpf_device { struct dma_device dma_dev; void __iomem *base; + u32 max_burst_mem_read; + u32 max_burst_mem_write; struct clk *clk; const struct nbpf_config *config; unsigned int eirq; @@ -425,10 +427,33 @@ static void nbpf_chan_configure(struct nbpf_channel *chan) nbpf_chan_write(chan, NBPF_CHAN_CFG, NBPF_CHAN_CFG_DMS | chan->dmarq_cfg); } -static u32 nbpf_xfer_ds(struct nbpf_device *nbpf, size_t size) +static u32 nbpf_xfer_ds(struct nbpf_device *nbpf, size_t size, + enum dma_transfer_direction direction) { + int max_burst = nbpf->config->buffer_size * 8; + + if (nbpf->max_burst_mem_read || nbpf->max_burst_mem_write) { + switch (direction) { + case DMA_MEM_TO_MEM: + max_burst = min_not_zero(nbpf->max_burst_mem_read, + nbpf->max_burst_mem_write); + break; + case DMA_MEM_TO_DEV: + if (nbpf->max_burst_mem_read) + max_burst = nbpf->max_burst_mem_read; + break; + case DMA_DEV_TO_MEM: + if (nbpf->max_burst_mem_write) + max_burst = nbpf->max_burst_mem_write; + break; + case DMA_DEV_TO_DEV: + default: + break; + } + } + /* Maximum supported bursts depend on the buffer size */ - return min_t(int, __ffs(size), ilog2(nbpf->config->buffer_size * 8)); + return min_t(int, __ffs(size), ilog2(max_burst)); } static size_t nbpf_xfer_size(struct nbpf_device *nbpf, @@ -458,7 +483,7 @@ static size_t nbpf_xfer_size(struct nbpf_device *nbpf, size = burst; } - return nbpf_xfer_ds(nbpf, size); + return nbpf_xfer_ds(nbpf, size, DMA_TRANS_NONE); } /* @@ -507,7 +532,7 @@ static int nbpf_prep_one(struct nbpf_link_desc *ldesc, * transfers we enable the SBE bit and terminate the transfer in our * .device_pause handler. */ - mem_xfer = nbpf_xfer_ds(chan->nbpf, size); + mem_xfer = nbpf_xfer_ds(chan->nbpf, size, direction); switch (direction) { case DMA_DEV_TO_MEM: @@ -1313,6 +1338,11 @@ static int nbpf_probe(struct platform_device *pdev) if (IS_ERR(nbpf->clk)) return PTR_ERR(nbpf->clk); + of_property_read_u32(np, "max-burst-mem-read", + &nbpf->max_burst_mem_read); + of_property_read_u32(np, "max-burst-mem-write", + &nbpf->max_burst_mem_write); + nbpf->config = cfg; for (i = 0; irqs < ARRAY_SIZE(irqbuf); i++) { -- 2.45.2