Messages in this thread | | | Date | Thu, 11 May 2023 15:22:13 +0200 | From | Artur Rojek <> | Subject | Re: [PATCH v6 5/6] fbdev: Move framebuffer I/O helpers into <asm/fb.h> |
| |
On 2023-05-11 14:35, Geert Uytterhoeven wrote: > Hi Arnd, > > CC Artur, who's working on HP Jornada 680. Thanks for CC'ing me - I faced this exact issue while working on my (still not upstreamed) hd6446x PCMCIA controller driver. The PCMCIA subsystem uses `inb/outb`, which expect the `sh_io_port_base` to be set to something else than the default `-1`. At first I tried to set it to `0xa0000000`, so that all I/O goes through the fixed, non-cacheable P2 area. That however broke some other driver code (I had no time to debug which one). Eventually I ended up taking a suggestion from a MIPS PCMCIA driver [1] and simply substract the broken `sh_io_port_base` address from `HD64461_IOBASE`, as the base for `socket.io_offset`. This way all the PCMCIA `inb/outb` accesses are absolute, no matter what the `sh_io_port_base` is set to. This of course is a very ugly solution and we should instead fix the root cause of this mess. I will have a better look at this patch set and the problem at hand at a later date.
Cheers, Artur
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pcmcia/db1xxx_ss.c?h=v6.4-rc1#n527
> > On Wed, May 10, 2023 at 5:55 PM Arnd Bergmann <arnd@arndb.de> wrote: >> On Wed, May 10, 2023, at 16:27, Thomas Zimmermann wrote: >> > Am 10.05.23 um 16:15 schrieb Arnd Bergmann: >> >> On Wed, May 10, 2023, at 16:03, kernel test robot wrote: >> >> >> I think that's a preexisting bug and I have no idea what the >> >> correct solution is. Looking for HD64461 shows it being used >> >> both with inw/outw and readw/writew, so there is no way to have >> >> the correct type. The sh __raw_readw() definition hides this bug, >> >> but that is a problem with arch/sh and it probably hides others >> >> as well. >> > >> > The constant HD64461_IOBASE is defined as integer at >> > >> > >> > https://elixir.bootlin.com/linux/latest/source/arch/sh/include/asm/hd64461.h#L17 >> > >> > but fb_readw() expects a volatile-void pointer. I guess we could add a >> > cast somewhere to silence the problem. In the current upstream code, >> > that appears to be done by sh's __raw_readw() internally: >> > >> > >> > https://elixir.bootlin.com/linux/latest/source/arch/sh/include/asm/io.h#L35 >> >> Sure, that would make it build again, but that still doesn't make the >> code correct, since it's completely unclear what base address the >> HD64461_IOBASE is relative to. The hp6xx platform code only passes it >> through inw()/outw(), which take an offset relative to >> sh_io_port_base, >> but that is not initialized on hp6xx. I tried to find in the history >> when it broke, apparently that was in 2007 commit 34a780a0afeb ("sh: >> hp6xx pata_platform support."), which removed the custom inw/outw >> implementations. > > See also commit 4aafae27d0ce73f8 ("sh: hd64461 tidying."), which > claims they are no longer needed. > > Don't the I/O port macros just treat the port as an absolute base > address > when sh_io_port_base isn't set? > > Gr{oetje,eeting}s, > > Geert
| |