| Message ID | 20190625121321.10197-1-hch@lst.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | au1200fb: don't use DMA_ATTR_NON_CONSISTENT | expand |
On Tue, Jun 25, 2019 at 2:13 PM Christoph Hellwig <hch@lst.de> wrote: > > au1200fb allocates DMA memory using DMA_ATTR_NON_CONSISTENT, but never > calls dma_cache_sync to synchronize the memory between the CPU and the > device. If it was use on a not cache coherent bus that would be fatal, > but as far as I can tell from the naming and the mips platform > implementation it always is used in cache coherent systems. Remove > the DMA_ATTR_NON_CONSISTENT flag, which is a no-op in that case. Very early au1200 chips, on which this driver apparently was developed on, had issues with cache coherency, but this was fixed in a later step, none of the 3 steppings I have access to exhibit any problems with this patch applied. > Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-By: Manuel Lauss <manuel.lauss@gmail.com>
On 6/26/19 9:16 AM, Manuel Lauss wrote: > On Tue, Jun 25, 2019 at 2:13 PM Christoph Hellwig <hch@lst.de> wrote: >> >> au1200fb allocates DMA memory using DMA_ATTR_NON_CONSISTENT, but never >> calls dma_cache_sync to synchronize the memory between the CPU and the >> device. If it was use on a not cache coherent bus that would be fatal, >> but as far as I can tell from the naming and the mips platform >> implementation it always is used in cache coherent systems. Remove >> the DMA_ATTR_NON_CONSISTENT flag, which is a no-op in that case. > > Very early au1200 chips, on which this driver apparently was developed on, > had issues with cache coherency, but this was fixed in a later step, > none of the 3 steppings I have access to exhibit any problems > with this patch applied. > >> Signed-off-by: Christoph Hellwig <hch@lst.de> > > Acked-By: Manuel Lauss <manuel.lauss@gmail.com> Patch queued for v5.4, thanks. Best regards, -- Bartlomiej Zolnierkiewicz Samsung R&D Institute Poland Samsung Electronics
diff --git a/drivers/video/fbdev/au1200fb.c b/drivers/video/fbdev/au1200fb.c index 26caffb02b7e..265d3b45efd0 100644 --- a/drivers/video/fbdev/au1200fb.c +++ b/drivers/video/fbdev/au1200fb.c @@ -1234,7 +1234,7 @@ static int au1200fb_fb_mmap(struct fb_info *info, struct vm_area_struct *vma) struct au1200fb_device *fbdev = info->par; return dma_mmap_attrs(fbdev->dev, vma, fbdev->fb_mem, fbdev->fb_phys, - fbdev->fb_len, DMA_ATTR_NON_CONSISTENT); + fbdev->fb_len, 0); } static void set_global(u_int cmd, struct au1200_lcd_global_regs_t *pdata) @@ -1692,8 +1692,7 @@ static int au1200fb_drv_probe(struct platform_device *dev) fbdev->fb_mem = dmam_alloc_attrs(&dev->dev, PAGE_ALIGN(fbdev->fb_len), - &fbdev->fb_phys, GFP_KERNEL, - DMA_ATTR_NON_CONSISTENT); + &fbdev->fb_phys, GFP_KERNEL, 0); if (!fbdev->fb_mem) { print_err("fail to allocate framebuffer (size: %dK))", fbdev->fb_len / 1024);
au1200fb allocates DMA memory using DMA_ATTR_NON_CONSISTENT, but never calls dma_cache_sync to synchronize the memory between the CPU and the device. If it was use on a not cache coherent bus that would be fatal, but as far as I can tell from the naming and the mips platform implementation it always is used in cache coherent systems. Remove the DMA_ATTR_NON_CONSISTENT flag, which is a no-op in that case. Signed-off-by: Christoph Hellwig <hch@lst.de> --- drivers/video/fbdev/au1200fb.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)