[Nouveau] Fix unaligned accesses for SPARC

[Patrick Baggett]

Marcin,

I had the same messages on NV17, which worked extremely well (OpenGL games
worked fine). The kernel will properly emulate the unaligned access, it
just causes a trap which is slow. If the unaligned access caused an error,
the NV17 card would have been unable to function given the number of
erroneous accesses.

Using __get_unaligned_le would probably remove one byteswap though.

Patrick

On Wed, Mar 13, 2013 at 4:29 PM, Marcin Slusarz <marcin.slusarz at gmail.com>wrote:

> On Tue, Mar 12, 2013 at 10:18:41PM -0500, Patrick Baggett wrote:
> >    The nouveau driver makes a number of unaligned accesses via the
> >    ROM16(), ROM32() and ROM64() macros which fault on SPARC (but would be
> >    transparently handled by x86 hardware). Making use of get_unaligned()
> >    macro fixes the problem for me.
> >
> >    diff --git a/drivers/gpu/drm/nouveau/nouveau_bios.h
> >    b/drivers/gpu/drm/nouveau/nouveau_bios.h
> >    index 7ccd28f..92031f6 100644
> >    --- a/drivers/gpu/drm/nouveau/nouveau_bios.h
> >    +++ b/drivers/gpu/drm/nouveau/nouveau_bios.h
> >    @@ -26,6 +26,8 @@
> >     #include "nvreg.h"
> >    +#include <asm/unaligned.h>
> >    +
> >     #define DCB_MAX_NUM_ENTRIES 16
> >     #define DCB_MAX_NUM_I2C_ENTRIES 16
> >     #define DCB_MAX_NUM_GPIO_ENTRIES 32
> >    @@ -33,10 +35,10 @@
> >     #define DCB_LOC_ON_CHIP 0
> >    -#define ROM16(x) le16_to_cpu(*(u16 *)&(x))
> >    -#define ROM32(x) le32_to_cpu(*(u32 *)&(x))
> >    +#define ROM16(x) le16_to_cpu(get_unaligned((u16 *)&(x)))
> >    +#define ROM32(x) le32_to_cpu(get_unaligned((u32 *)&(x)))
> >     #define ROM48(x) ({ u8 *p = &(x); (u64)ROM16(p[4]) << 32 |
> >    ROM32(p[0]); })
> >    -#define ROM64(x) le64_to_cpu(*(u64 *)&(x))
> >    +#define ROM64(x) le64_to_cpu(get_unaligned((u64 *)&(x)))
> >     #define ROMPTR(d,x) ({            \
> >            struct nouveau_drm *drm = nouveau_drm((d)); \
> >            ROM16(x) ? &drm->vbios.data[ROM16(x)] : NULL; \
>
> Please take a look at Documentation/SubmittingPatches and resubmit after
> adapting.
>
> IMHO, I think you should submit this patch only once you figure out how to
> correctly boot and use at least basic accelerated operations, because I'm
> not
> 100% sure this is correct - 1. you have other severe issues with nouveau
> which
> may or may not be connected to this code, 2. sparc defines get_unaligned to
> __get_unaligned_be, so maybe you need to use _le variant? or maybe use
> get_unaligned_le* without le*_to_cpu?.
>
> Marcin
>
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