[PATCH V2 6/6] coresight-stm: adding driver for CoreSight STM component

On Friday 05 February 2016 15:06:20 Alexander Shishkin wrote:

Chunyan Zhang [off-list ref] writes:

quoted

+#ifndef CONFIG_64BIT
+static inline void __raw_writeq(u64 val, volatile void __iomem *addr)
+{
+     asm volatile("strd %1, %0"
+                  : "+Qo" (*(volatile u64 __force *)addr)
+                  : "r" (val));
+}

Is it really ok to do this for all !64bit arms, inside a driver, just
like that? I'm not an expert, but I'm pretty sure there's more to it.

It's normally device dependent whether this works or not, on 32-bit
architectures, a 64-bit access to an I/O bus tends to get split into
two 32 bit accesses and the order might not be the as what was
intended.

We have functions in include/linux/io-64-nonatomic-hi-lo.h
and include/linux/io-64-nonatomic-lo-hi.h that are meant to
do this right. Maybe the driver can be changed to use whichever
one is correct for it.

	Arnd