Re: [PATCH] offb: Fix little-endian support

[Takashi Iwai]

At Wed, 14 May 2014 19:04:00 +0200,
Cedric Le Goater wrote:
> 
> On 05/14/2014 04:24 PM, Takashi Iwai wrote:
> > At Wed, 14 May 2014 16:01:17 +0200,
> > Cedric Le Goater wrote:
> >>
> >> Hi Iwai-san,
> >>
> >> On 05/14/2014 03:21 PM, Takashi Iwai wrote:
> >>> Although the color palette was corrected for little endian by the
> >>> commit  [e1edf18b: offb: Add palette hack for little endian], the
> >>> graphics mode is still shown in psychedelic colors.  
> >>
> >> Are you referring to the linux logo colors ? If so, could you please
> >> try the patch below, it should be a fix.
> > 
> > Not only penguin logo but the whole X graphics got strange colors,
> > too, according to the bug report.  I put the original reporter/tester
> > (Dinar Valeev) to Cc.
> > I'm merely a person who tries to fix this mess ;)
> > 
> > BTW, did you try to run X on fbdev?
> 
> Not at the time, I was working on the console only, BE and LE. 
> I just tried fbdev and indeed this is a psychedelic mess :)
> 
> Your fix has also issues on BE and console and the patch of mine 
> below is of no use for fbdev. Damn, this is a nightmare.

Hm, so it actually regressed on BE?

It's strange because fb_math_be() should be true and the patch won't
change the values in that case...


Takashi

> 
> C. 
> 
> >>> For fixing this
> >>> properly, we rather need to correct the RGB offsets depending on
> >>> endianess.
> >>>
> >>> Since the RGB base offsets are corrected, we don't need the hack for
> >>> pallette color entries.  This patch reverts that, too.
> >>
> >> Are you testing using qemu -vga std -vnc :x ? If so, did you try changing 
> >> the depth to 8,15,16,32 ?
> > 
> > Yes, it was with qemu -vga std -vnc :x.
> > About different color depths, Dinar can test / clarify better, I
> > suppose.
> > 
> >>  I think the patch might be breaking big endian 
> >> too.
> > 
> > Big endian should work as is because my patch uses the original
> > offsets when fb_be_math() is true.  It corrects the RGB offsets if
> > !fb_be_math().
> >
> > But, I'm also entirely not sure whether this is 100% correct, either.
> > Namely, if the RGB offsets were correct for some little endian
> > machines with offb, my patch would break it, of course.  But, then
> > your previous fix must have already broken it as well, so I took the
> > same fb_be_math() check.
> > 
> > 
> > thanks,
> > 
> > Takashi
> > 
> >> Now, I am far from being an expert on frame buffers. It would be glad 
> >> to have some insights on that topic. 
> >>
> >> Thanks,
> >>
> >> C. 
> >>
> >>
> >> [PATCH] fb: fix logo palette entries for little endian
> >>
> >> The offb_cmap_byteswap() routine helps byteswapping the color map
> >> entries when required. This patch externalizes and renames the helper 
> >> routine to adjust the pseudo palette of the logo when running on 
> >> little endian.
> >>
> >> Signed-off-by: CÃdric Le Goater <clg@xxxxxxxxxx>
> >> ---
> >>  drivers/video/fbmem.c |    6 ++++--
> >>  drivers/video/offb.c  |   11 +----------
> >>  include/linux/fb.h    |    8 ++++++++
> >>  3 files changed, 13 insertions(+), 12 deletions(-)
> >>
> >> Index: linux.git/drivers/video/fbmem.c
> >> ===================================================================
> >> --- linux.git.orig/drivers/video/fbmem.c
> >> +++ linux.git/drivers/video/fbmem.c
> >> @@ -252,7 +252,8 @@ static void  fb_set_logo_truepalette(str
> >>  	blueshift  = info->var.blue.offset  - (8 - info->var.blue.length);
> >>  
> >>  	for ( i = 0; i < logo->clutsize; i++) {
> >> -		palette[i+32] = (safe_shift((clut[0] & redmask), redshift) |
> >> +		palette[i+32] = fb_cmap_byteswap(info,
> >> +				 safe_shift((clut[0] & redmask), redshift) |
> >>  				 safe_shift((clut[1] & greenmask), greenshift) |
> >>  				 safe_shift((clut[2] & bluemask), blueshift));
> >>  		clut += 3;
> >> @@ -271,7 +272,8 @@ static void fb_set_logo_directpalette(st
> >>  	blueshift = info->var.blue.offset;
> >>  
> >>  	for (i = 32; i < 32 + logo->clutsize; i++)
> >> -		palette[i] = i << redshift | i << greenshift | i << blueshift;
> >> +		palette[i] = fb_cmap_byteswap(info, i << redshift |
> >> +					i << greenshift | i << blueshift);
> >>  }
> >>  
> >>  static void fb_set_logo(struct fb_info *info,
> >> Index: linux.git/drivers/video/offb.c
> >> ===================================================================
> >> --- linux.git.orig/drivers/video/offb.c
> >> +++ linux.git/drivers/video/offb.c
> >> @@ -91,15 +91,6 @@ extern boot_infos_t *boot_infos;
> >>  #define AVIVO_DC_LUTB_WHITE_OFFSET_GREEN        0x6cd4
> >>  #define AVIVO_DC_LUTB_WHITE_OFFSET_RED          0x6cd8
> >>  
> >> -#define FB_RIGHT_POS(p, bpp)         (fb_be_math(p) ? 0 : (32 - (bpp)))
> >> -
> >> -static inline u32 offb_cmap_byteswap(struct fb_info *info, u32 value)
> >> -{
> >> -	u32 bpp = info->var.bits_per_pixel;
> >> -
> >> -	return cpu_to_be32(value) >> FB_RIGHT_POS(info, bpp);
> >> -}
> >> -
> >>      /*
> >>       *  Set a single color register. The values supplied are already
> >>       *  rounded down to the hardware's capabilities (according to the
> >> @@ -129,7 +120,7 @@ static int offb_setcolreg(u_int regno, u
> >>  			mask <<= info->var.transp.offset;
> >>  			value |= mask;
> >>  		}
> >> -		pal[regno] = offb_cmap_byteswap(info, value);
> >> +		pal[regno] = fb_cmap_byteswap(info, value);
> >>  		return 0;
> >>  	}
> >>  
> >> Index: linux.git/include/linux/fb.h
> >> ===================================================================
> >> --- linux.git.orig/include/linux/fb.h
> >> +++ linux.git/include/linux/fb.h
> >> @@ -582,6 +582,7 @@ static inline struct apertures_struct *a
> >>  
> >>  #endif
> >>  
> >> +#define FB_RIGHT_POS(p, bpp)         (fb_be_math(p) ? 0 : (32 - (bpp)))
> >>  #define FB_LEFT_POS(p, bpp)          (fb_be_math(p) ? (32 - (bpp)) : 0)
> >>  #define FB_SHIFT_HIGH(p, val, bits)  (fb_be_math(p) ? (val) >> (bits) : \
> >>  						      (val) << (bits))
> >> @@ -681,6 +682,13 @@ static inline bool fb_be_math(struct fb_
> >>  #endif /* CONFIG_FB_FOREIGN_ENDIAN */
> >>  }
> >>  
> >> +static inline u32 fb_cmap_byteswap(struct fb_info *info, u32 value)
> >> +{
> >> +	u32 bpp = info->var.bits_per_pixel;
> >> +
> >> +	return cpu_to_be32(value) >> FB_RIGHT_POS(info, bpp);
> >> +}
> >> +
> >>  /* drivers/video/fbsysfs.c */
> >>  extern struct fb_info *framebuffer_alloc(size_t size, struct device *dev);
> >>  extern void framebuffer_release(struct fb_info *info);
> >>
> > 
> 
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