From: Niklas Cassel <niklas.cassel@xxxxxxxx>
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 <niklas.cassel@xxxxxxxx>
---
Documentation/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++) {
--
2.1.4
--
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