linux-kernel - Re: [PATCH, RFC] unicore32: remove swiotlb support

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Date:   Sat, 29 Sep 2018 21:40:27 +0800 (GMT+08:00)
From:   "Guan Xuetao" <gxt@....edu.cn>
To:     "christoph hellwig" <hch@....de>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RFC] unicore32: remove swiotlb support

That's right and really good to use direct.c, not swiotlb.c
No special limitation for dma zone in unicore32.

Acked-by: Guan Xuetao <gxt@....edu.cn>

Thanks,

Guan Xuetao

> -----Original Messages-----
> From: "Christoph Hellwig" <hch@....de>
> Sent Time: 2018-09-27 21:54:34 (Thursday)
> To: "Guan Xuetao" <gxt@....edu.cn>
> Cc: iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
> Subject: [PATCH, RFC] unicore32: remove swiotlb support
> 
> unicore32 is a bog standard 32-bit port without larger physical address
> space, highmem or any other obvious addressing limitation.  There should
> be no need to bounce buffer using swiotlb.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
> 
> Guan, can you double check my assumptions?  I really can't find a
> reason why unicore32 would need swiotlb.
> 
>  arch/unicore32/Kconfig                   |  2 +-
>  arch/unicore32/include/asm/Kbuild        |  1 +
>  arch/unicore32/include/asm/dma-mapping.h | 22 ----------------------
>  arch/unicore32/mm/init.c                 |  3 ---
>  4 files changed, 2 insertions(+), 26 deletions(-)
>  delete mode 100644 arch/unicore32/include/asm/dma-mapping.h
> 
> diff --git a/arch/unicore32/Kconfig b/arch/unicore32/Kconfig
> index 60eae744d8fd..3a3b40f79558 100644
> --- a/arch/unicore32/Kconfig
> +++ b/arch/unicore32/Kconfig
> @@ -4,6 +4,7 @@ config UNICORE32
>  	select ARCH_HAS_DEVMEM_IS_ALLOWED
>  	select ARCH_MIGHT_HAVE_PC_PARPORT
>  	select ARCH_MIGHT_HAVE_PC_SERIO
> +	select DMA_DIRECT_OPS
>  	select HAVE_MEMBLOCK
>  	select HAVE_GENERIC_DMA_COHERENT
>  	select HAVE_KERNEL_GZIP
> @@ -20,7 +21,6 @@ config UNICORE32
>  	select GENERIC_IOMAP
>  	select MODULES_USE_ELF_REL
>  	select NEED_DMA_MAP_STATE
> -	select SWIOTLB
>  	help
>  	  UniCore-32 is 32-bit Instruction Set Architecture,
>  	  including a series of low-power-consumption RISC chip
> diff --git a/arch/unicore32/include/asm/Kbuild b/arch/unicore32/include/asm/Kbuild
> index bfc7abe77905..1372553dc0a9 100644
> --- a/arch/unicore32/include/asm/Kbuild
> +++ b/arch/unicore32/include/asm/Kbuild
> @@ -4,6 +4,7 @@ generic-y += compat.h
>  generic-y += current.h
>  generic-y += device.h
>  generic-y += div64.h
> +generic-y += dma-mapping.h
>  generic-y += emergency-restart.h
>  generic-y += exec.h
>  generic-y += extable.h
> diff --git a/arch/unicore32/include/asm/dma-mapping.h b/arch/unicore32/include/asm/dma-mapping.h
> deleted file mode 100644
> index 790bc2ef4af2..000000000000
> --- a/arch/unicore32/include/asm/dma-mapping.h
> +++ /dev/null
> @@ -1,22 +0,0 @@
> -/*
> - * linux/arch/unicore32/include/asm/dma-mapping.h
> - *
> - * Code specific to PKUnity SoC and UniCore ISA
> - *
> - * Copyright (C) 2001-2010 GUAN Xue-tao
> - *
> - * This program is free software; you can redistribute it and/or modify
> - * it under the terms of the GNU General Public License version 2 as
> - * published by the Free Software Foundation.
> - */
> -#ifndef __UNICORE_DMA_MAPPING_H__
> -#define __UNICORE_DMA_MAPPING_H__
> -
> -#include <linux/swiotlb.h>
> -
> -static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
> -{
> -	return &swiotlb_dma_ops;
> -}
> -
> -#endif
> diff --git a/arch/unicore32/mm/init.c b/arch/unicore32/mm/init.c
> index f4950fbfe574..5f72a8d1d953 100644
> --- a/arch/unicore32/mm/init.c
> +++ b/arch/unicore32/mm/init.c
> @@ -234,9 +234,6 @@ void __init bootmem_init(void)
>  
>  	uc32_bootmem_init(min, max_low);
>  
> -#ifdef CONFIG_SWIOTLB
> -	swiotlb_init(1);
> -#endif
>  	/*
>  	 * Sparsemem tries to allocate bootmem in memory_present(),
>  	 * so must be done after the fixed reservations
> -- 
> 2.19.0