[U-Boot] usb: dwc2: invalidate the dcache before starting the DMA

[Kever Yang]

Hi Eddie,


     We should only need to do only one time cache operation for a buffer

ready to do DMA transfer, so you need to remove another cache invalidate

operation for the same buffer in the same function.


Thanks,
- Kever
On 04/01/2017 02:51 PM, 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 at gmail.com>
> ---
>   drivers/usb/host/dwc2.c | 17 +++++++++++------
>   1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/host/dwc2.c b/drivers/usb/host/dwc2.c
> index 5ac602e..a151ba6 100644
> --- a/drivers/usb/host/dwc2.c
> +++ b/drivers/usb/host/dwc2.c
> @@ -811,12 +811,17 @@ 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 +
> +					   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);