Hi Am 02.05.23 um 22:06 schrieb Arnd Bergmann: > On Tue, May 2, 2023, at 15:02, Thomas Zimmermann wrote: >> Implement framebuffer I/O helpers, such as fb_read*() and fb_write*(), >> in the architecture's header file or the generic one. >> >> The common case has been the use of regular I/O functions, such as >> __raw_readb() or memset_io(). A few architectures used plain system- >> memory reads and writes. Sparc used helpers for its SBus. >> >> The architectures that used special cases provide the same code in >> their __raw_*() I/O helpers. So the patch replaces this code with the >> __raw_*() functions and moves it to for all >> architectures. >> >> v3: >> * implement all architectures with generic helpers >> * support reordering and native byte order (Geert, Arnd) > > This looks good for the read/write helpers, but I'm a little > worried about the memset and memcpy functions, since they do > change behavior on some architectures: > > - on sparc64, fb_mem{set,cpy} uses ASI_PHYS_BYPASS_EC_E (like __raw_readb) > while mem{set_,cpy_from,cpy_to} uses ASI_PHYS_BYPASS_EC_E_L (like readb) > I don't know the effect of that, but it seems intentional > > - on loongarch and csky, the _io variants avoid unaligned access, > while the normal memcpy/memset is probably broken, so your > patch is a bugfix > > - on ia64, the _io variants use bytewise access and avoid any longer > loads and stores, so your patch probably makes things slower. > > It's probably safe to deal with all the above by either adding > architecture specific overrides to the current version, or > by doing the semantic changes before the move to asm/fb.h, but > one way or the other I'd prefer this to be separate from the > consolidation patch that should not have any changes in behavior. I think I'll add architecture overrides that contain the current code, even if they contain some force-casting wrt __iomem. If anyone wants to fix the issues, they can then address them easily. Best regards Thomas > > Arnd -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)