Hi
2017-04-18 11:55 GMT+08:00 Kever Yang kever.yang@rock-chips.com:
Hi Marek,
On 04/06/2017 06:20 PM, Marek Vasut wrote:
On 04/06/2017 10:34 AM, Kever Yang wrote:
Hi Eddie,
On 04/06/2017 10:14 AM, Marek Vasut wrote:
On 04/06/2017 04:03 AM, Eddie Cai wrote:
We should invalidate the dcache before starting the DMA. In case there are any dirty lines from the DMA buffer in the cache, subsequent cache-line replacements may corrupt the buffer in memory while the DMA is still going on. Cache-line replacement can happen if the CPU tries to bring some other memory locations into the cache while the DMA is going on.
Signed-off-by: Eddie Cai eddie.cai.linux@gmail.com Reviewed-by: Stefan Brüns stefan.bruens@rwth-aachen.de
drivers/usb/host/dwc2.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/drivers/usb/host/dwc2.c b/drivers/usb/host/dwc2.c index 5ac602e..e3a5d7d 100644 --- a/drivers/usb/host/dwc2.c +++ b/drivers/usb/host/dwc2.c @@ -811,12 +811,19 @@ static int transfer_chunk(struct dwc2_hc_regs *hc_regs, void *aligned_buffer, (*pid << DWC2_HCTSIZ_PID_OFFSET), &hc_regs->hctsiz);
- if (!in && xfer_len) {
memcpy(aligned_buffer, buffer, xfer_len);flush_dcache_range((unsigned long)aligned_buffer,(unsigned long)aligned_buffer +roundup(xfer_len, ARCH_DMA_MINALIGN));
- if (xfer_len) {
if (in) {invalidate_dcache_range((unsigned long)aligned_buffer,(unsigned long)aligned_buffer +Should be uintptr_t all over the place to deal with 32/64 bit systems, otherwise great, thanks.
roundup(xfer_len, ARCH_DMA_MINALIGN));
} else {memcpy(aligned_buffer, buffer, xfer_len);flush_dcache_range((unsigned long)aligned_buffer,(unsigned long)aligned_buffer +roundup(xfer_len, ARCH_DMA_MINALIGN));} } writel(phys_to_bus((unsigned long)aligned_buffer),&hc_regs->hcdma);
Did you test with remove another invalidate_dcache_range() in this
function? I still think no need to have 2 invalidate_dcache in this function.
You need the first invalidate to prevent having data stuck in the cache and accidentally being evicted into the RAM while the USB DMA is also running , thus creating a total mess of the result.
Yes, I'm very clear about what happen here, because it's me report the origin bug. What I mean is the fix should be _move_ the invalidate_dcache_range() operation from "after start DMA transfer" to "before DMA transter" for in transfer, but not _add_ a invalidate_dcache_range() operation.
I follow doc/README.arm-caches. I says Peripheral to Memory DMA:
- Invalidate the buffer before starting the DMA. In case there are any dirty lines from the DMA buffer in the cache, subsequent cache-line replacements may corrupt the buffer in memory while the DMA is still going on. Cache-line replacement can happen if the CPU tries to bring some other memory locations into the cache while the DMA is going on.
- Invalidate the buffer after the DMA is complete and before the MPU reads
it. This may be needed in addition to the invalidation before the DMA
mentioned above, because in some processors memory contents can spontaneously come to the cache due to speculative memory access by the CPU. If this
happens with the DMA buffer while DMA is going on we have a coherency problem. I guess that means we need to Invalidate the buffer before and after the DMA Thanks Eddie
If you apply this patch, then there will be two invalidate_dcache_range() operation for in transfer, and the second one is no need, because CPU should not have any access to the buffer during dma start and done.
Thanks,
- Kever