[PATCHv8 1/4] pwm: Add Freescale FTM PWM driver support

Hi Arnd,

Adding Greg here to make sure we have a common understanding in the future.

ioread*() was indeed introduced for devices that can be both I/O and memory
space, and is a bit slowed than readl() on architectures that don't have
memory mapped I/O space (i.e. x86).

However, ioread32be is the only architecture-independent big-endian
accessor function (some architectures have in_be32, but that doesn't
work on ARM), and as mandated by Linus a couple of years ago when
we wanted to take some shortcuts on powerpc, ioread32 has to be
semantically the same as readl when used on pointers returned from
ioremap() rather than ioport_map, and ioread32be is just the
byte-swapped version of it.

We have a couple of drivers using ioread* because of the need for
big-endian data access, and I would continue recommending that unless
I hear a good argument against it.

quoted

The big-endian supports is added at v7~v8 patch series.

Yes, that version looks fine and it avoids the above problem nicely,
but I'd still like to make sure we come to a conclusion on the problem
of big-endian I/O accessors.

How about the following ?
-----
+static inline u32 ftm_readl(struct fsl_pwm_chip *fpc, unsigned long reg)
+{
+       if (fpc->big_endian)
+               return ioread32be(fpc->base + reg);
+       else
+               return ioread32(fpc->base + reg);
+}
+
+static inline void ftm_writel(struct fsl_pwm_chip *fpc, u32 val,
+                             unsigned long reg)
+{
+       if (fpc->big_endian)
+               iowrite32be(val, fpc->base + reg);
+       else
+               iowrite32(val, fpc->base + reg);
+}
------

I'll send another version soon.
Does this patch series has other problems needed to fix or revise ?

Thanks,

Best Regards,
Xiubo