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Re: [PATCH V15 01/12] MIPS: Loongson: Add basic Loongson-3 definition

To: Huacai Chen <chenhc@lemote.com>
Subject: Re: [PATCH V15 01/12] MIPS: Loongson: Add basic Loongson-3 definition
From: Aurelien Jarno <aurelien@aurel32.net>
Date: Mon, 30 Dec 2013 22:09:10 +0100
Cc: Ralf Baechle <ralf@linux-mips.org>, John Crispin <john@phrozen.org>, "Steven J. Hill" <Steven.Hill@imgtec.com>, linux-mips@linux-mips.org, Fuxin Zhang <zhangfx@lemote.com>, Zhangjin Wu <wuzhangjin@gmail.com>, Hongliang Tao <taohl@lemote.com>, Hua Yan <yanh@lemote.com>
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On Sun, Dec 15, 2013 at 08:14:25PM +0800, Huacai Chen wrote:
> Loongson-3 is a multi-core MIPS family CPU, it support MIPS64R2 fully.
> Loongson-3 has the same IMP field (0x6300) as Loongson-2.
> 
> Loongson-3 has a hardware-maintained cache, system software doesn't
> need to maintain coherency.
> 
> Loongson-3A is the first revision of Loongson-3, and it is the quad-
> core version of Loongson-2G. Loongson-3A has a simplified version named
> Loongson-2Gq, the main difference between Loongson-3A/2Gq is 3A has two
> HyperTransport controller but 2Gq has only one. HT0 is used for cross-
> chip interconnection and HT1 is used to link PCI bus. Therefore, 2Gq
> cannot support NUMA but 3A can. For software, Loongson-2Gq is simply
> identified as Loongson-3A.
> 
> Exsisting Loongson family CPUs:
> Loongson-1: Loongson-1A, Loongson-1B, they are 32-bit MIPS CPUs.
> Loongson-2: Loongson-2E, Loongson-2F, Loongson-2G, they are 64-bit
>             single-core MIPS CPUs.
> Loongson-3: Loongson-3A(including so-called Loongson-2Gq), they are
>             64-bit multi-core MIPS CPUs.
> 
> Signed-off-by: Huacai Chen <chenhc@lemote.com>
> Signed-off-by: Hongliang Tao <taohl@lemote.com>
> Signed-off-by: Hua Yan <yanh@lemote.com>
> ---
>  arch/mips/include/asm/addrspace.h            |    2 ++
>  arch/mips/include/asm/cpu.h                  |    5 +++--
>  arch/mips/include/asm/mach-loongson/spaces.h |   19 +++++++++++++++++++
>  arch/mips/include/asm/module.h               |    2 ++
>  arch/mips/include/asm/pgtable-bits.h         |    7 +++++++
>  5 files changed, 33 insertions(+), 2 deletions(-)
>  create mode 100644 arch/mips/include/asm/mach-loongson/spaces.h
> 
> diff --git a/arch/mips/include/asm/addrspace.h 
> b/arch/mips/include/asm/addrspace.h
> index 3f74545..41c030e 100644
> --- a/arch/mips/include/asm/addrspace.h
> +++ b/arch/mips/include/asm/addrspace.h
> @@ -116,7 +116,9 @@
>  #define K_CALG_UNCACHED              2
>  #define K_CALG_NONCOHERENT   3
>  #define K_CALG_COH_EXCL              4
> +#ifndef K_CALG_COH_SHAREABLE
>  #define K_CALG_COH_SHAREABLE 5
> +#endif
>  #define K_CALG_NOTUSED               6
>  #define K_CALG_UNCACHED_ACCEL        7
>  
> diff --git a/arch/mips/include/asm/cpu.h b/arch/mips/include/asm/cpu.h
> index d2035e1..7fffaf1 100644
> --- a/arch/mips/include/asm/cpu.h
> +++ b/arch/mips/include/asm/cpu.h
> @@ -224,6 +224,7 @@
>  #define PRID_REV_LOONGSON1B  0x0020
>  #define PRID_REV_LOONGSON2E  0x0002
>  #define PRID_REV_LOONGSON2F  0x0003
> +#define PRID_REV_LOONGSON3A  0x0005
>  
>  /*
>   * Older processors used to encode processor version and revision in two
> @@ -295,8 +296,8 @@ enum cpu_type_enum {
>        * MIPS64 class processors
>        */
>       CPU_5KC, CPU_5KE, CPU_20KC, CPU_25KF, CPU_SB1, CPU_SB1A, CPU_LOONGSON2,
> -     CPU_CAVIUM_OCTEON, CPU_CAVIUM_OCTEON_PLUS, CPU_CAVIUM_OCTEON2,
> -     CPU_CAVIUM_OCTEON3, CPU_XLR, CPU_XLP,
> +     CPU_LOONGSON3, CPU_CAVIUM_OCTEON, CPU_CAVIUM_OCTEON_PLUS,
> +     CPU_CAVIUM_OCTEON2, CPU_CAVIUM_OCTEON3, CPU_XLR, CPU_XLP,
>  
>       CPU_LAST
>  };
> diff --git a/arch/mips/include/asm/mach-loongson/spaces.h 
> b/arch/mips/include/asm/mach-loongson/spaces.h
> new file mode 100644
> index 0000000..e32c9ad
> --- /dev/null
> +++ b/arch/mips/include/asm/mach-loongson/spaces.h
> @@ -0,0 +1,19 @@
> +#ifndef __ASM_MACH_LOONGSON_SPACES_H_
> +#define __ASM_MACH_LOONGSON_SPACES_H_
> +
> +#ifndef CAC_BASE
> +#if defined(CONFIG_64BIT)
> +#if defined(CONFIG_DMA_NONCOHERENT) || defined(CONFIG_CPU_LOONGSON3)
> +#define CAC_BASE        _AC(0x9800000000000000, UL)
> +#else
> +#define CAC_BASE        _AC(0xa800000000000000, UL)
> +#endif /* CONFIG_DMA_NONCOHERENT || CONFIG_CPU_LOONGSON3 */
> +#endif /* CONFIG_64BIT */
> +#endif /* CONFIG_CAC_BASE */
> +

The value for Loongson 3A is correct and correspond to the one in the user
manual. It comes from the fact that Loongson 3A only have cache and
coherency attribute 2 (uncached), 3 (cached) and 7 (uncached
accelerated), and not 5 like some other CPU have for cacheable coherent
exclusive on write. This is perfectly fine as only values 2 and 3 are
required, the others are available for implementation dependent use.

That said it's already the case for the Loongson 2E and 2F according to
their respective manuals, even if 3 is non coherent there. So it looks
like the wrong value is used for Loongson 2E and 2F, even though it
obviously work.

I therefore suggest to use 0x9800000000000000 for all 64-bit Loongson
CPUs and get rid of the #ifdefs that do not really make sense here.

> +#ifdef CONFIG_CPU_LOONGSON3
> +#define K_CALG_COH_SHAREABLE 3
> +#endif
> +

This is the same here, the value should be 3 for Loongson 2E, 2F and 3A

> +#include <asm/mach-generic/spaces.h>
> +#endif
> diff --git a/arch/mips/include/asm/module.h b/arch/mips/include/asm/module.h
> index 44b705d..c2edae3 100644
> --- a/arch/mips/include/asm/module.h
> +++ b/arch/mips/include/asm/module.h
> @@ -126,6 +126,8 @@ search_module_dbetables(unsigned long addr)
>  #define MODULE_PROC_FAMILY "LOONGSON1 "
>  #elif defined CONFIG_CPU_LOONGSON2
>  #define MODULE_PROC_FAMILY "LOONGSON2 "
> +#elif defined CONFIG_CPU_LOONGSON3
> +#define MODULE_PROC_FAMILY "LOONGSON3 "
>  #elif defined CONFIG_CPU_CAVIUM_OCTEON
>  #define MODULE_PROC_FAMILY "OCTEON "
>  #elif defined CONFIG_CPU_XLR
> diff --git a/arch/mips/include/asm/pgtable-bits.h 
> b/arch/mips/include/asm/pgtable-bits.h
> index 32aea48..6c1e99e 100644
> --- a/arch/mips/include/asm/pgtable-bits.h
> +++ b/arch/mips/include/asm/pgtable-bits.h
> @@ -235,6 +235,13 @@ static inline uint64_t pte_to_entrylo(unsigned long 
> pte_val)
>  #define _CACHE_CACHABLE_NONCOHERENT (5<<_CACHE_SHIFT)
>  #define _CACHE_UNCACHED_ACCELERATED (7<<_CACHE_SHIFT)
>  
> +#elif defined(CONFIG_CPU_LOONGSON3)
> +
> +#define _CACHE_UNCACHED             (2<<_CACHE_SHIFT)  /* LOONGSON       */
> +#define _CACHE_CACHABLE_NONCOHERENT (3<<_CACHE_SHIFT)  /* LOONGSON       */
> +#define _CACHE_CACHABLE_COHERENT    (3<<_CACHE_SHIFT)  /* LOONGSON-3     */
> +#define _CACHE_UNCACHED_ACCELERATED (7<<_CACHE_SHIFT)  /* LOONGSON       */
> +
>  #else

This is fine but you should probably add an explanation why the same
value is used for both coherent and non-coherent, like it is done a few
line above for SB1.

>  #define _CACHE_CACHABLE_NO_WA            (0<<_CACHE_SHIFT)  /* R4600 only    
>   */

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net

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