Re: [Linux-fbdev-devel] Re: [PATCH] fbdev: Fix IO access in rivafb

On Tuesday 09 November 2004 04:13, Linus Torvalds wrote:

On Tue, 9 Nov 2004, Antonino A. Daplas wrote:

quoted

In big endian machines, the read*/write* accessors do a byteswap for an
inherently little endian PCI bus.  However, rivafb puts the hardwire in
big endian register access, thus the byteswap is not needed. So, instead
of read*/write*, use __raw_read*/__raw_write*.

This fix should make the #ifdef CONFIG_PCC entirely superfluous afaik.

Ah, of course.

The thing is, once riva does its HW accesses right, the special cases just
go away. There's a reason we have abstractions..

Does anybody have the hardware to test with?

I've asked Guido Guenther to test, might take a couple of days.  I also
asked him if he can use the in/out_be* which is probably safer for ppc.
And the mb()'s scattered all over the driver may be removed. 

Tony


In big endian machines, the read*/write* accessors do a byteswap for an
inherently little endian PCI bus.  However, rivafb puts the hardwire in big
endian register access, thus the byteswap is not needed. So for 16- and
32-bit access, instead of read*/write*, use __raw_read*/__raw_write* for all
archs.
 
Signed-off-by: Antonino Daplas <redacted>
---

diff -Nru a/drivers/video/riva/riva_hw.h b/drivers/video/riva/riva_hw.h

--- a/drivers/video/riva/riva_hw.h	2004-11-09 05:39:48 +08:00
+++ b/drivers/video/riva/riva_hw.h	2004-11-09 06:00:09 +08:00

@@ -73,18 +73,13 @@
 /*
  * HW access macros.
  */
-#if defined(__powerpc__)
 #include <asm/io.h>
-#define NV_WR08(p,i,d)	out_8(p+i, d)
-#define NV_RD08(p,i)	in_8(p+i)
-#else
 #define NV_WR08(p,i,d)  (writeb((d), (u8 __iomem *)(p) + (i)))
 #define NV_RD08(p,i)    (readb((u8 __iomem *)(p) + (i)))
-#endif
-#define NV_WR16(p,i,d)  (writew((d), (u16 __iomem *)(p) + (i)/2))
-#define NV_RD16(p,i)    (readw((u16 __iomem *)(p) + (i)/2))
-#define NV_WR32(p,i,d)  (writel((d), (u32 __iomem *)(p) + (i)/4))
-#define NV_RD32(p,i)    (readl((u32 __iomem *)(p) + (i)/4))
+#define NV_WR16(p,i,d)  (__raw_writew((d), (u16 __iomem *)(p) + (i)/2))
+#define NV_RD16(p,i)    (__raw_readw((u16 __iomem *)(p) + (i)/2))
+#define NV_WR32(p,i,d)  (__raw_writel((d), (u32 __iomem *)(p) + (i)/4))
+#define NV_RD32(p,i)    (__raw_readl((u32 __iomem *)(p) + (i)/4))
 #define VGA_WR08(p,i,d) NV_WR08(p,i,d)
 #define VGA_RD08(p,i)   NV_RD08(p,i)