Hi Robin,
Thanks for your comment。 At 2024-10-17 01:38:23, "Robin Murphy" <robin.mur...@arm.com> wrote: >On 2024-09-20 9:20 am, Andy Yan wrote: >> From: Andy Yan <andy....@rock-chips.com> >> >> The vop mmu support translate physical address upper 4 GB to iova >> below 4 GB. So set dma mask to 64 bit to indicate we support address >>> 4GB. >> >> This can avoid warnging message like this on some boards with DDR >>> 4 GB: >> >> rockchip-drm display-subsystem: swiotlb buffer is full (sz: 266240 bytes), >> total 32768 (slots), used 130 (slots) >> rockchip-drm display-subsystem: swiotlb buffer is full (sz: 266240 bytes), >> total 32768 (slots), used 0 (slots) >> rockchip-drm display-subsystem: swiotlb buffer is full (sz: 266240 bytes), >> total 32768 (slots), used 130 (slots) >> rockchip-drm display-subsystem: swiotlb buffer is full (sz: 266240 bytes), >> total 32768 (slots), used 130 (slots) >> rockchip-drm display-subsystem: swiotlb buffer is full (sz: 266240 bytes), >> total 32768 (slots), used 0 (slots) > >There are several things wrong with this... > >AFAICS the VOP itself still only supports 32-bit addresses, so the VOP >driver should only be setting a 32-bit DMA mask. The IOMMUs support >either 32-bit or 40-bit addresses, and the IOMMU driver does set its DMA Does that mean we can only use the dev of IOMMU ? If that is true， would you please give some inspiration on how to implement this? Or is there any other diver i can follow。Very sorry for that I'm not familiar with memory management and the IOMMU。 >mask appropriately. None of those numbers is 64, so that's clearly >suspicious already. Plus it would seem the claim of the IOMMU being able >to address >4GB isn't strictly true for RK3288 (which does supposedly >support 8GB of RAM). We can set DMA mask per device if we can find a right way to do it。 > >Furthermore, the "display-subsystem" doesn't even exist - it does not >represent any actual DMA-capable hardware, so it should not have a DMA >mask, and it should not be used for DMA API operations. Buffers for the >VOP should be DMA-mapped for the VOP device itself. At the very least >the rockchip_gem_alloc_dma() path is clearly broken otherwise (I guess >this patch possibly *would* make that brokenness apparent). > >> Signed-off-by: Andy Yan <andy....@rock-chips.com> >> Tested-by: Derek Foreman <derek.fore...@collabora.com> >> --- >> >> (no changes since v1) >> >> drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c >> b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c >> index 04ef7a2c3833..8bc2ff3b04bb 100644 >> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c >> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c >> @@ -445,7 +445,9 @@ static int rockchip_drm_platform_probe(struct >> platform_device *pdev) >> return ret; >> } >> >> - return 0; >> + ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(64)); > >Finally as a general thing, please don't misuse >dma_coerce_mask_and_coherent() in platform drivers, just use normal >dma_set_mask_and_coherent(). The platform bus code has been initialising >the dev->dma_mask pointer for years now, drivers should not be messing >with it any more. Got it ， thanks again。 > >Thanks, >Robin. > >> + >> + return ret; >> } >> >> static void rockchip_drm_platform_remove(struct platform_device *pdev)
