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Date:   Mon, 4 Dec 2023 11:05:00 -0800
From:   Charlie Jenkins <charlie@rivosinc.com>
To:     Jisheng Zhang <jszhang@kernel.org>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] riscv: Use asm-generic for {read,write}{bwlq} and
 their relaxed variant
Message-ID: <ZW4i3MqVRg21RmRV@ghost>
References: <20231202133813.4003-1-jszhang@kernel.org>
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On Sat, Dec 02, 2023 at 09:38:13PM +0800, Jisheng Zhang wrote:
> The asm-generic implementation is functionally identical to the riscv
> version. At the same time, the readl{q}_relaxed is replaced with the
> raw version for nommu building.
> 
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
> 
> Since v1:
>  - fix nommu build
> 
>  arch/riscv/include/asm/mmio.h  | 62 +---------------------------------
>  arch/riscv/include/asm/timex.h |  6 ++--
>  2 files changed, 4 insertions(+), 64 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/mmio.h b/arch/riscv/include/asm/mmio.h
> index 4c58ee7f95ec..a491590593ca 100644
> --- a/arch/riscv/include/asm/mmio.h
> +++ b/arch/riscv/include/asm/mmio.h
> @@ -80,54 +80,7 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
>  #endif
>  
>  /*
> - * Unordered I/O memory access primitives.  These are even more relaxed than
> - * the relaxed versions, as they don't even order accesses between successive
> - * operations to the I/O regions.
> - */
> -#define readb_cpu(c)		({ u8  __r = __raw_readb(c); __r; })
> -#define readw_cpu(c)		({ u16 __r = le16_to_cpu((__force __le16)__raw_readw(c)); __r; })
> -#define readl_cpu(c)		({ u32 __r = le32_to_cpu((__force __le32)__raw_readl(c)); __r; })
> -
> -#define writeb_cpu(v, c)	((void)__raw_writeb((v), (c)))
> -#define writew_cpu(v, c)	((void)__raw_writew((__force u16)cpu_to_le16(v), (c)))
> -#define writel_cpu(v, c)	((void)__raw_writel((__force u32)cpu_to_le32(v), (c)))
> -
> -#ifdef CONFIG_64BIT
> -#define readq_cpu(c)		({ u64 __r = le64_to_cpu((__force __le64)__raw_readq(c)); __r; })
> -#define writeq_cpu(v, c)	((void)__raw_writeq((__force u64)cpu_to_le64(v), (c)))
> -#endif
> -
> -/*
> - * Relaxed I/O memory access primitives. These follow the Device memory
> - * ordering rules but do not guarantee any ordering relative to Normal memory
> - * accesses.  These are defined to order the indicated access (either a read or
> - * write) with all other I/O memory accesses to the same peripheral. Since the
> - * platform specification defines that all I/O regions are strongly ordered on
> - * channel 0, no explicit fences are required to enforce this ordering.
> - */
> -/* FIXME: These are now the same as asm-generic */
> -#define __io_rbr()		do {} while (0)
> -#define __io_rar()		do {} while (0)
> -#define __io_rbw()		do {} while (0)
> -#define __io_raw()		do {} while (0)
> -
> -#define readb_relaxed(c)	({ u8  __v; __io_rbr(); __v = readb_cpu(c); __io_rar(); __v; })
> -#define readw_relaxed(c)	({ u16 __v; __io_rbr(); __v = readw_cpu(c); __io_rar(); __v; })
> -#define readl_relaxed(c)	({ u32 __v; __io_rbr(); __v = readl_cpu(c); __io_rar(); __v; })
> -
> -#define writeb_relaxed(v, c)	({ __io_rbw(); writeb_cpu((v), (c)); __io_raw(); })
> -#define writew_relaxed(v, c)	({ __io_rbw(); writew_cpu((v), (c)); __io_raw(); })
> -#define writel_relaxed(v, c)	({ __io_rbw(); writel_cpu((v), (c)); __io_raw(); })
> -
> -#ifdef CONFIG_64BIT
> -#define readq_relaxed(c)	({ u64 __v; __io_rbr(); __v = readq_cpu(c); __io_rar(); __v; })
> -#define writeq_relaxed(v, c)	({ __io_rbw(); writeq_cpu((v), (c)); __io_raw(); })
> -#endif
> -
> -/*
> - * I/O memory access primitives.  Reads are ordered relative to any following
> - * Normal memory read and delay() loop.  Writes are ordered relative to any
> - * prior Normal memory write.  The memory barriers here are necessary as RISC-V
> + * I/O barriers. The memory barriers here are necessary as RISC-V
>   * doesn't define any ordering between the memory space and the I/O space.
>   */
>  #define __io_br()	do {} while (0)
> @@ -135,17 +88,4 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
>  #define __io_bw()	({ __asm__ __volatile__ ("fence w,o" : : : "memory"); })
>  #define __io_aw()	mmiowb_set_pending()
>  
> -#define readb(c)	({ u8  __v; __io_br(); __v = readb_cpu(c); __io_ar(__v); __v; })
> -#define readw(c)	({ u16 __v; __io_br(); __v = readw_cpu(c); __io_ar(__v); __v; })
> -#define readl(c)	({ u32 __v; __io_br(); __v = readl_cpu(c); __io_ar(__v); __v; })
> -
> -#define writeb(v, c)	({ __io_bw(); writeb_cpu((v), (c)); __io_aw(); })
> -#define writew(v, c)	({ __io_bw(); writew_cpu((v), (c)); __io_aw(); })
> -#define writel(v, c)	({ __io_bw(); writel_cpu((v), (c)); __io_aw(); })
> -
> -#ifdef CONFIG_64BIT
> -#define readq(c)	({ u64 __v; __io_br(); __v = readq_cpu(c); __io_ar(__v); __v; })
> -#define writeq(v, c)	({ __io_bw(); writeq_cpu((v), (c)); __io_aw(); })
> -#endif
> -
>  #endif /* _ASM_RISCV_MMIO_H */
> diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h
> index a06697846e69..9ff9f398f61a 100644
> --- a/arch/riscv/include/asm/timex.h
> +++ b/arch/riscv/include/asm/timex.h
> @@ -17,18 +17,18 @@ typedef unsigned long cycles_t;
>  #ifdef CONFIG_64BIT
>  static inline cycles_t get_cycles(void)
>  {
> -	return readq_relaxed(clint_time_val);
> +	return __raw_readq(clint_time_val);
>  }
>  #else /* !CONFIG_64BIT */
>  static inline u32 get_cycles(void)
>  {
> -	return readl_relaxed(((u32 *)clint_time_val));
> +	return __raw_readl(((u32 *)clint_time_val));
>  }
>  #define get_cycles get_cycles
>  
>  static inline u32 get_cycles_hi(void)
>  {
> -	return readl_relaxed(((u32 *)clint_time_val) + 1);
> +	return __raw_readl(((u32 *)clint_time_val) + 1);
>  }
>  #define get_cycles_hi get_cycles_hi
>  #endif /* CONFIG_64BIT */
> -- 
> 2.42.0
> 
> 
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Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>