Den 20.04.2016 19:44, skrev Daniel Vetter: > On Wed, Apr 20, 2016 at 05:25:26PM +0200, Noralf Trønnes wrote: >> Export fb_deferred_io_mmap so drivers can change vma->vm_page_prot. >> When the framebuffer memory is allocated using dma_alloc_writecombine() >> instead of vmalloc(), I get cache syncing problems. >> This solves it: >> >> static int drm_fbdev_cma_deferred_io_mmap(struct fb_info *info, >> struct vm_area_struct *vma) >> { >> fb_deferred_io_mmap(info, vma); >> vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot); > Hm, do we need pgpropt_writecombine? There recently was some discussion > (on the arc platform) that fbdev pgprots need to be fixed up in fbdev > code. I have no idea, just repeating from memory ...
I need it or else I get partial lines that doesn't get updated on the display. fbdev code that doesn't set (struct fb_ops *)->fb_mmap, gets this for free in the default fb_mmap implementation (drivers/video/fbdev/core/fbmem.c). It calls fb_pgprotect() at the end which is an architecture specific function that on many platforms uses pgprot_writecombine(), but not on all. And looking at some of the fb_mmap implementations, some of them sets vm_page_prot to nocache for instance, so I think the safest bet is to do this here and not in the fbdev core. And we can't call fb_pgprotect() from fb_deferred_io_mmap() either because we don't have access to the file pointer that powerpc needs. I think the case you refer to was solved with using fb_pgprotect() for the platform in question and it didn't involve deferred io. > -Daniel > >> return 0; >> } >> >> Signed-off-by: Noralf Trønnes <noralf at tronnes.org> >> --- >> drivers/video/fbdev/core/fb_defio.c | 3 ++- >> include/linux/fb.h | 1 + >> 2 files changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/video/fbdev/core/fb_defio.c >> b/drivers/video/fbdev/core/fb_defio.c >> index 57721c7..74b5bca 100644 >> --- a/drivers/video/fbdev/core/fb_defio.c >> +++ b/drivers/video/fbdev/core/fb_defio.c >> @@ -164,7 +164,7 @@ static const struct address_space_operations >> fb_deferred_io_aops = { >> .set_page_dirty = fb_deferred_io_set_page_dirty, >> }; >> >> -static int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct >> *vma) >> +int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma) >> { >> vma->vm_ops = &fb_deferred_io_vm_ops; >> vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP; >> @@ -173,6 +173,7 @@ static int fb_deferred_io_mmap(struct fb_info *info, >> struct vm_area_struct *vma) >> vma->vm_private_data = info; >> return 0; >> } >> +EXPORT_SYMBOL(fb_deferred_io_mmap); >> >> /* workqueue callback */ >> static void fb_deferred_io_work(struct work_struct *work) >> diff --git a/include/linux/fb.h b/include/linux/fb.h >> index dfe8835..a964d07 100644 >> --- a/include/linux/fb.h >> +++ b/include/linux/fb.h >> @@ -673,6 +673,7 @@ static inline void __fb_pad_aligned_buffer(u8 *dst, u32 >> d_pitch, >> } >> >> /* drivers/video/fb_defio.c */ >> +int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma); >> extern void fb_deferred_io_init(struct fb_info *info); >> extern void fb_deferred_io_open(struct fb_info *info, >> struct inode *inode, >> -- >> 2.2.2 >>