Thx Arnd,
On Tue, Jul 30, 2019 at 9:43 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
>
> On Tue, Jul 30, 2019 at 2:16 PM <guoren@xxxxxxxxxx> wrote:
> > From: Guo Ren <ren_guo@xxxxxxxxx>
>
> > diff --git a/arch/csky/mm/dma-mapping.c b/arch/csky/mm/dma-mapping.c
> > index 3f1ff9d..d8f0f81 100644
> > --- a/arch/csky/mm/dma-mapping.c
> > +++ b/arch/csky/mm/dma-mapping.c
> > @@ -72,6 +72,8 @@ void arch_sync_dma_for_device(struct device *dev, phys_addr_t paddr,
> > cache_op(paddr, size, dma_wb_range);
> > break;
> > case DMA_FROM_DEVICE:
> > + cache_op(paddr, size, dma_inv_range);
> > + break;
> > case DMA_BIDIRECTIONAL:
> > cache_op(paddr, size, dma_wbinv_range);
> > break;
> > @@ -88,6 +90,8 @@ void arch_sync_dma_for_cpu(struct device *dev, phys_addr_t paddr,
> > cache_op(paddr, size, dma_wb_range);
> > break;
> > case DMA_FROM_DEVICE:
> > + cache_op(paddr, size, dma_inv_range);
> > + break;
> > case DMA_BIDIRECTIONAL:
> > cache_op(paddr, size, dma_wbinv_range);
> > break;
>
> When syncing 'for_cpu', you should not need to write back, because
> there won't be any dirty cache lines.
I just follow the dma_data_direction param, seems dir param and
function are a little bit duplicated. And our cpu won't clear clean
cache line into memory, so dma_wb_page won't cause problem.
Seems arch_sync_dma_for_cpu with dir=DMA_TO_DEVICE is self-contradictory.
Do you want me modfiy like these:
@@ -88,6 +90,8 @@ void arch_sync_dma_for_cpu(struct device *dev,
phys_addr_t paddr,
case DMA_TO_DEVICE:
case DMA_FROM_DEVICE:
case DMA_BIDIRECTIONAL:
cache_op(paddr, size, dma_inv_range);
break;
@@ -72,6 +72,8 @@ void arch_sync_dma_for_device(struct device *dev,
phys_addr_t paddr,
case DMA_TO_DEVICE:
cache_op(paddr, size, dma_wb_range);
break;
case DMA_FROM_DEVICE:
case DMA_BIDIRECTIONAL:
cache_op(paddr, size, dma_wbinv_range);
break;
>
> If you have a CPU core that does not do speculative loads, you also don't
> need to invalidate here, because you have already done that in the
> _for_device() case, the only reason to invalidate the CPU cache
> again is if a speculative load created a stale cache line that now
> shadows the data received from the device.
Our CPU support speculative loads :)
--
Best Regards
Guo Ren
ML: https://lore.kernel.org/linux-csky/
