On Thu, 25 Nov 2004, Linux Kernel Mailing List wrote:
> ChangeSet 1.1543, 2004/11/25 13:16:49-02:00, [email protected]
>
> [PATCH] vga16fb: Fix frame buffer bad memory mapping
>
> The vga16fb driver uses a direct ioremap on 0xa00000 to gain access to
> the vga card. This is wrong on architectures other than x86, every
> other driver uses VGA_MAP_MEM macro from vga.h to ensure the correct
> memory mapping.
>
> All this patch does is add the mapping macro this has been tested and
> works on ARM systems The driver no longer maps parts of kernel
> workspace and modifies it.
This fix is not correct!
> diff -Nru a/drivers/video/vga16fb.c b/drivers/video/vga16fb.c
> --- a/drivers/video/vga16fb.c 2004-11-25 15:01:51 -08:00
> +++ b/drivers/video/vga16fb.c 2004-11-25 15:01:51 -08:00
> @@ -142,7 +142,7 @@
> memset(fix, 0, sizeof(struct fb_fix_screeninfo));
> strcpy(fix->id,"VGA16 VGA");
>
> - fix->smem_start = VGA_FB_PHYS;
> + fix->smem_start = VGA_MAP_MEM(VGA_FB_PHYS);
> fix->smem_len = VGA_FB_PHYS_LEN;
> fix->type = FB_TYPE_VGA_PLANES;
> fix->visual = FB_VISUAL_PSEUDOCOLOR;
fix->smem_start: Although I agree VGA_FB_PHYS is not the correct value on
machines other than PC, VGA_MAP_MEM(VGA_FB_PHYS) is not appropriate either,
because fix->smem_start is supposed to be a CPU _physical_ address, not a
virtual address.
However, this value isn't really used, except by (very rare) userspace that
wants to mmap the frame buffer through /dev/mem instead of /dev/fb*, so an
incorrect value doesn't really harm.
> @@ -896,7 +896,7 @@
>
> /* XXX share VGA_FB_PHYS region with vgacon */
>
> - vga16fb.video_vbase = ioremap(VGA_FB_PHYS, VGA_FB_PHYS_LEN);
> + vga16fb.video_vbase = ioremap(VGA_MAP_MEM(VGA_FB_PHYS), VGA_FB_PHYS_LEN);
> if (!vga16fb.video_vbase) {
> printk(KERN_ERR "vga16fb: unable to map device\n");
> return -ENOMEM;
ioremap(): VGA_MAP_MEM() already a _virtual_ address:
| include/asm-alpha/vga.h:#define VGA_MAP_MEM(x) ((unsigned long) ioremap((x), 0))
| include/asm-arm/vga.h:#define VGA_MAP_MEM(x) (PCIMEM_BASE + (x))
| include/asm-i386/vga.h:#define VGA_MAP_MEM(x) (unsigned long)phys_to_virt(x)
| include/asm-ia64/vga.h:#define VGA_MAP_MEM(x) ((unsigned long) ioremap((x), 0))
| include/asm-mips/vga.h:#define VGA_MAP_MEM(x) ((unsigned long)0xb0000000 + (unsigned long)(x))
| include/asm-ppc/vga.h:#define VGA_MAP_MEM(x) (x + vgacon_remap_base)
| include/asm-ppc64/vga.h:#define VGA_MAP_MEM(x) ((unsigned long) ioremap((x), 0))
| include/asm-sparc64/vga.h:#define VGA_MAP_MEM(x) (x)
| include/asm-x86_64/vga.h:#define VGA_MAP_MEM(x) (unsigned long)phys_to_virt(x)
Doing a double ioremap(), or ioremap(phys_to_virt()) will break for sure...
BTW, on (PReP/CHRP) PPC ioremap() on ISA memory space `just works' because
__ioremap() adds _ISA_MEM_BASE to the passed pointer if it's smaller than
16*1024*1024. And yes, vga16fb used to work fine on my CHRP LongTrail
(before the machine itself died :-(.
Yes, ISA memory space is a mess to do right in a portable way...
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
On Sat, Nov 27, 2004 at 04:54:12PM +0100, Geert Uytterhoeven wrote:
> On Thu, 25 Nov 2004, Linux Kernel Mailing List wrote:
> > ChangeSet 1.1543, 2004/11/25 13:16:49-02:00, [email protected]
> >
> > [PATCH] vga16fb: Fix frame buffer bad memory mapping
> >
> > The vga16fb driver uses a direct ioremap on 0xa00000 to gain access to
> > the vga card. This is wrong on architectures other than x86, every
> > other driver uses VGA_MAP_MEM macro from vga.h to ensure the correct
> > memory mapping.
> >
> > All this patch does is add the mapping macro this has been tested and
> > works on ARM systems The driver no longer maps parts of kernel
> > workspace and modifies it.
>
> This fix is not correct!
>
> > diff -Nru a/drivers/video/vga16fb.c b/drivers/video/vga16fb.c
> > --- a/drivers/video/vga16fb.c 2004-11-25 15:01:51 -08:00
> > +++ b/drivers/video/vga16fb.c 2004-11-25 15:01:51 -08:00
> > @@ -142,7 +142,7 @@
> > memset(fix, 0, sizeof(struct fb_fix_screeninfo));
> > strcpy(fix->id,"VGA16 VGA");
> >
> > - fix->smem_start = VGA_FB_PHYS;
> > + fix->smem_start = VGA_MAP_MEM(VGA_FB_PHYS);
> > fix->smem_len = VGA_FB_PHYS_LEN;
> > fix->type = FB_TYPE_VGA_PLANES;
> > fix->visual = FB_VISUAL_PSEUDOCOLOR;
>
> fix->smem_start: Although I agree VGA_FB_PHYS is not the correct value on
> machines other than PC, VGA_MAP_MEM(VGA_FB_PHYS) is not appropriate either,
> because fix->smem_start is supposed to be a CPU _physical_ address, not a
> virtual address.
>
> However, this value isn't really used, except by (very rare) userspace that
> wants to mmap the frame buffer through /dev/mem instead of /dev/fb*, so an
> incorrect value doesn't really harm.
>
> > @@ -896,7 +896,7 @@
> >
> > /* XXX share VGA_FB_PHYS region with vgacon */
> >
> > - vga16fb.video_vbase = ioremap(VGA_FB_PHYS, VGA_FB_PHYS_LEN);
> > + vga16fb.video_vbase = ioremap(VGA_MAP_MEM(VGA_FB_PHYS), VGA_FB_PHYS_LEN);
> > if (!vga16fb.video_vbase) {
> > printk(KERN_ERR "vga16fb: unable to map device\n");
> > return -ENOMEM;
>
> ioremap(): VGA_MAP_MEM() already a _virtual_ address:
>
> | include/asm-alpha/vga.h:#define VGA_MAP_MEM(x) ((unsigned long) ioremap((x), 0))
> | include/asm-arm/vga.h:#define VGA_MAP_MEM(x) (PCIMEM_BASE + (x))
> | include/asm-i386/vga.h:#define VGA_MAP_MEM(x) (unsigned long)phys_to_virt(x)
> | include/asm-ia64/vga.h:#define VGA_MAP_MEM(x) ((unsigned long) ioremap((x), 0))
> | include/asm-mips/vga.h:#define VGA_MAP_MEM(x) ((unsigned long)0xb0000000 + (unsigned long)(x))
> | include/asm-ppc/vga.h:#define VGA_MAP_MEM(x) (x + vgacon_remap_base)
> | include/asm-ppc64/vga.h:#define VGA_MAP_MEM(x) ((unsigned long) ioremap((x), 0))
> | include/asm-sparc64/vga.h:#define VGA_MAP_MEM(x) (x)
> | include/asm-x86_64/vga.h:#define VGA_MAP_MEM(x) (unsigned long)phys_to_virt(x)
>
> Doing a double ioremap(), or ioremap(phys_to_virt()) will break for sure...
>
> BTW, on (PReP/CHRP) PPC ioremap() on ISA memory space `just works' because
> __ioremap() adds _ISA_MEM_BASE to the passed pointer if it's smaller than
> 16*1024*1024. And yes, vga16fb used to work fine on my CHRP LongTrail
> (before the machine itself died :-(.
>
> Yes, ISA memory space is a mess to do right in a portable way...
Geert,
I'll guest I'll just revert the whole change then... Do you have a
better suggestion?
Thanks!