Re: [PATCHv6 1/5] arm64: io: Use asm-generic high level MMIO accessors

[Catalin Marinas <catalin.marinas@arm.com>]

On Tue, Dec 07, 2021 at 12:24:45PM +0530, Sai Prakash Ranjan wrote:
> Remove custom arm64 MMIO accessors read{b,w,l,q} and their relaxed
> versions in support to use asm-generic defined accessors. Also define
> one set of IO barriers (ar/bw version) used by asm-generic code to
> override the arm64 specific variants.
> 
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Sai Prakash Ranjan <quic_saipraka@quicinc.com>
> ---
>  arch/arm64/include/asm/io.h | 41 ++++++++-----------------------------
>  1 file changed, 8 insertions(+), 33 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
> index 7fd836bea7eb..1b436810d779 100644
> --- a/arch/arm64/include/asm/io.h
> +++ b/arch/arm64/include/asm/io.h
> @@ -91,7 +91,7 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
>  }
>  
>  /* IO barriers */
> -#define __iormb(v)							\
> +#define __io_ar(v)							\
>  ({									\
>  	unsigned long tmp;						\
>  									\
> @@ -108,39 +108,14 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
>  		     : "memory");					\
>  })
>  
> -#define __io_par(v)		__iormb(v)
> -#define __iowmb()		dma_wmb()
> -#define __iomb()		dma_mb()
> -
> -/*
> - * Relaxed I/O memory access primitives. These follow the Device memory
> - * ordering rules but do not guarantee any ordering relative to Normal memory
> - * accesses.
> - */
> -#define readb_relaxed(c)	({ u8  __r = __raw_readb(c); __r; })
> -#define readw_relaxed(c)	({ u16 __r = le16_to_cpu((__force __le16)__raw_readw(c)); __r; })
> -#define readl_relaxed(c)	({ u32 __r = le32_to_cpu((__force __le32)__raw_readl(c)); __r; })
> -#define readq_relaxed(c)	({ u64 __r = le64_to_cpu((__force __le64)__raw_readq(c)); __r; })
> +#define __io_bw()		dma_wmb()
> +#define __io_br(v)
> +#define __io_aw(v)
>  
> -#define writeb_relaxed(v,c)	((void)__raw_writeb((v),(c)))
> -#define writew_relaxed(v,c)	((void)__raw_writew((__force u16)cpu_to_le16(v),(c)))
> -#define writel_relaxed(v,c)	((void)__raw_writel((__force u32)cpu_to_le32(v),(c)))
> -#define writeq_relaxed(v,c)	((void)__raw_writeq((__force u64)cpu_to_le64(v),(c)))
> -
> -/*
> - * I/O memory access primitives. Reads are ordered relative to any
> - * following Normal memory access. Writes are ordered relative to any prior
> - * Normal memory access.
> - */
> -#define readb(c)		({ u8  __v = readb_relaxed(c); __iormb(__v); __v; })
> -#define readw(c)		({ u16 __v = readw_relaxed(c); __iormb(__v); __v; })
> -#define readl(c)		({ u32 __v = readl_relaxed(c); __iormb(__v); __v; })
> -#define readq(c)		({ u64 __v = readq_relaxed(c); __iormb(__v); __v; })
> -
> -#define writeb(v,c)		({ __iowmb(); writeb_relaxed((v),(c)); })
> -#define writew(v,c)		({ __iowmb(); writew_relaxed((v),(c)); })
> -#define writel(v,c)		({ __iowmb(); writel_relaxed((v),(c)); })
> -#define writeq(v,c)		({ __iowmb(); writeq_relaxed((v),(c)); })
> +/* arm64-specific, don't use in portable drivers */
> +#define __iormb(v)		__io_ar(v)
> +#define __iowmb()		__io_bw()
> +#define __iomb()		dma_mb()

More of a nitpick but I'd keep the __iormb()/__iowmb() as they currently
are and just define the generic __io_ar() etc. in terms of the former.

-- 
Catalin