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

Hi Arnd,

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

On Thursday 02 January 2014 17:57:01 Xiubo Li wrote:

quoted

+static inline u32 ftm_readl(bool big_endian, const void __iomem *addr)
+{
+       u32 val;
+
+       val = __raw_readl(addr);
+
+       if (likely(big_endian))
+               val = be32_to_cpu((__force __be32)val);
+       else
+               val = le32_to_cpu((__force __le32)val);
+       rmb();
+
+       return val;
+}
+
+static inline void ftm_writel(bool big_endian, u32 val, void __iomem *addr)
+{
+       wmb();
+       if (likely(big_endian))
+               val = (__force u32)cpu_to_be32(val);
+       else
+               val = (__force u32)cpu_to_le32(val);
+
+       __raw_writel(val, addr);

These functions definitely need some comments regarding why this is necessary.
I assume that after 8 rounds of review (that I did not read) this has been
discussed already, so please explain above the functions why you don't just
use ioread32be/ioread32 and iowrite32be/iowrite32 here.

As Thierry has commonts in some days before:
----
A few years ago GregKH commented in response to a patch that ioread*()
weren't supposed to be used for memory-mapped only devices. The original
purpose apparently was to allow drivers to work with both I/O and
memory-mapped devices.
----
I'm not very sure.

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

Also all callers seem to be of the style

       val = ftm_readl(fpc->big_endian, fpc->base + FTM_SC);

so I wonder why you don't just pass the fpc pointer to the function
and make it

static inline void ftm_readl(struct fsl_pwm_chip *fpc, unsigned long reg, u32
val)
{
	if (fpc->big_endian)
		iowrite32be(val, fpc->base + reg);
	else
		iowrite32(val, fpc->base + reg);
}

Yes, it was.

I thought this will make the ftm_readl/ftm_writel look more brief like other drivers.

 
Thanks very much.

--
Best Regards,
Xiubo