Hi Nicolas,
On 8 October 2013 10:57, Nicolas Pitre nicolas.pitre@linaro.org wrote:
On Tue, 8 Oct 2013, Dave Martin wrote:
On Mon, Oct 07, 2013 at 09:37:20PM -0700, Victor Kamensky wrote:
cci_enable_port_for_self written in asm and it works with h/w registers that are in little endian format. When run in big endian mode it needs byte swap before/after it writes/reads to/from such registers
Lorenzo should comment on this if he's not already seen it.
Signed-off-by: Victor Kamensky victor.kamensky@linaro.org
drivers/bus/arm-cci.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c index 2009266..6db173e 100644 --- a/drivers/bus/arm-cci.c +++ b/drivers/bus/arm-cci.c @@ -281,6 +281,9 @@ asmlinkage void __naked cci_enable_port_for_self(void) /* Enable the CCI port */ " ldr r0, [r0, %[offsetof_port_phys]] \n" " mov r3, #"__stringify(CCI_ENABLE_REQ)" \n" +#ifdef __ARMEB__ +" rev r3, r3 \n" +#endif /* __ARMEB__ */
Hmmm, this is a bit ugly, but we can't easily use ARM_BE8() here.
In any case, it would be more efficient to swap the CCI_ENABLE_REQ constant at compile time rather than doing it at run time with an extra instruction.
I could try to do this but it would require introducing another constant, because CCI_ENABLE_REQ is used in another place in writel_relaxed call which will do byteswap inside. Is such run-time optimization really worth it compared to code readability. Please let me know. I am OK either way. Personally I thought that run-time byteswap would be more readable.
Also I am concerned how can I compile time byteswap CCI_ENABLE_REQ in context of its being used with __stringify ... Wondering it should be stringfied into real number not long expression
Thanks, Victor
Nicolas