Re: [PATCH] m68k: io: Fix io{read,write}{16,32}be() for Coldfire peripherals

From: Greg Ungerer
Date: Tue Jun 04 2019 - 03:22:05 EST

Hi Angelo,

On 3/6/19 10:26 pm, Angelo Dureghello wrote:
couldn't seen any follow up on this patch. I tested it and at least
for mcf5441x it works properly and solves all issues.

Do you think it may be accepted as an initial fix ?

I'll add it to the m68knommu git tree.
Seeing as you wrote it Geert I assume you have no problem with that? :-)


On Mon, Apr 29, 2019 at 10:19:37AM +0200, Geert Uytterhoeven wrote:
The generic definitions of mmio_{read,write}{16,32}be() in lib/iomap.c
assume that the {read,write}[wl]() I/O accessors always use little
endian accesses, and swap the result.

However, the Coldfire versions of the {read,write}[wl]() I/O accessors are
special, in that they use native big endian instead of little endian for
accesses to the on-SoC peripheral block, thus violating the assumption.

Fix this by providing our own variants, using the raw accessors,
reinstating the old behavior. This is fine on m68k, as no special
barriers are needed, and also avoids swapping data twice.

Reported-by: Angelo Dureghello <angelo@xxxxxxxx>
Fixes: aecc787c06f4300f ("iomap: Use non-raw io functions for io{read|write}XXbe")
Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
This can be reverted later, after this oddity of the Coldfire I/O
support has been fixed, and drivers have been updated.
arch/m68k/include/asm/io.h | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/arch/m68k/include/asm/io.h b/arch/m68k/include/asm/io.h
index aabe6420ead2a599..d47e7384681ab1cd 100644
--- a/arch/m68k/include/asm/io.h
+++ b/arch/m68k/include/asm/io.h
@@ -8,6 +8,12 @@
#include <asm/io_mm.h>
+#define mmio_read16be(addr) __raw_readw(addr)
+#define mmio_read32be(addr) __raw_readl(addr)
+#define mmio_write16be(val, port) __raw_writew((val), (port))
+#define mmio_write32be(val, port) __raw_writel((val), (port))
#include <asm-generic/io.h>
#endif /* _M68K_IO_H */