Re: About commit "io: change inX() to have their own IO barrier overrides"

[John Garry]

On 06/03/2020 15:16, Arnd Bergmann wrote:
> On Fri, Mar 6, 2020 at 11:40 AM John Garry <john.garry@xxxxxxxxxx> wrote:
> > On 06/03/2020 07:54, Arnd Bergmann wrote:
> > > On Fri, Mar 6, 2020 at 4:44 AM Sinan Kaya <okaya@xxxxxxxxxx> wrote:
> > -- a/lib/logic_pio.c
> > +++ b/lib/logic_pio.c
> > @@ -229,13 +229,21 @@ unsigned long
> > logic_pio_trans_cpuaddr(resource_size_t addr)
> >    }
> >
> >    #if defined(CONFIG_INDIRECT_PIO) && defined(PCI_IOBASE)
> > +
> > +#define logic_in_to_cpu_b(x) (x)
> > +#define logic_in_to_cpu_w(x) __le16_to_cpu(x)
> > +#define logic_in_to_cpu_l(x) __le32_to_cpu(x)
> > +
> >    #define BUILD_LOGIC_IO(bw, type)                                      \

Note: The "bw" argument name could be improved to "bwl", since this 
macro is used for building inl() also.

> >    type logic_in##bw(unsigned long addr)                                 \
> >    {                                                                     \
> >           type ret = (type)~0;                                           \
> >                                                                          \
> >           if (addr < MMIO_UPPER_LIMIT) {                                 \
> > -               ret = read##bw(PCI_IOBASE + addr);                     \
> > +               void __iomem *_addr = PCI_IOBASE + addr;               \
> > +               __io_pbr();                                            \
> > +               ret = logic_in_to_cpu_##bw(__raw_read##bw(_addr));     \
> > +               __io_par(ret);                                         \
> >           } else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) {\
> >                   struct logic_pio_hwaddr *entry = find_io_rang
> >
> > We could prob combine the le_to_cpu and __raw_read into a single macro.
>
> What is the purpose of splitting out the byteswap rather than leaving the
> open-coded rather than __le16_to_cpu(__raw_readw(PCI_IOBASE + addr))?

I'm just copying what is in asm-generic io.h, which uses the 16b and 32b 
byteswaps in the w and l variants, respectively.

> If this is needed to work across architectures, how about adding
> an intermediate __raw_inw() etc in asm-generic/io.h like
>
> #ifndef __raw_inw
> #define __raw_inw(a) __raw_readw(PCI_IOBASE + addr));
> #endif
>
> #include <linux/logic_pio.h>
>
> #ifndef inw
> static inline u16 inw(unsigned long addr)
> {
>          u16 val;
>
>          __io_pbr();
>          val = __le16_to_cpu(__raw_inw(addr));
>          __io_par(val);
>          return val;
> }
> #endif

The idea is good, but it would be nice if we just somehow use a common 
asm-generic io.h definition directly in logic_pio.c, like:

asm-generic io.h:

#ifndef __raw_inw // name?
#define __raw_inw __raw_inw
static inline u16 __raw_inw(unsigned long addr)
{
	u16 val;

	__io_pbr();
	val = __le16_to_cpu(__raw_readw(addr));
	__io_par(val);
	return val;
}
#endif

#include <linux/logic_pio.h>

#ifndef inw
#define inw __raw_inw
#endif

logic_pio.c:

 #define BUILD_LOGIC_IO(bw, type)                                      \
 type logic_in##bw(unsigned long addr)                                 \
 {                                                                     \
        type ret = (type)~0;                                           \
                                                                       \
        if (addr < MMIO_UPPER_LIMIT) {                                 \
-               ret = read##bw(PCI_IOBASE + addr);                     \
+               ret = __raw_in##bw(PCI_IOBASE + addr);                 \
        } else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) {\
                struct logic_pio_hwaddr *entry = find_io_rang

Thanks,
John