linux-kernel - Re: [PATCH v2 4/7] sparc32: Do not select ZONE

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Message-ID: <8d5780f5-1047-48d7-a9c9-09b95c7b5604@gaisler.com>
Date: Tue, 5 Mar 2024 16:06:07 +0100
From: Andreas Larsson <andreas@...sler.com>
To: sam@...nborg.org, "Maciej W. Rozycki" <macro@...am.me.uk>,
 sparclinux@...r.kernel.org, Randy Dunlap <rdunlap@...radead.org>
Cc: Miquel Raynal <miquel.raynal@...tlin.com>,
 linux-parport@...ts.infradead.org, "David S. Miller" <davem@...emloft.net>,
 Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/7] sparc32: Do not select ZONE_DMA

On 2024-02-24 18:42, Sam Ravnborg via B4 Relay wrote:
> From: Sam Ravnborg <sam@...nborg.org>
> 
> sparc32 has no limited DMA zone so there is no need to select ZONE_DMA.
> 
> Based on analysis from Marciej:
> "
>     Actually I think ZONE_DMA should go too (it's linked to GENERIC_ISA_DMA,
>     isn't it? -- cf. commit 5ac6da669e24 ("[PATCH] Set CONFIG_ZONE_DMA for
>     arches with GENERIC_ISA_DMA")), and the whole thing use:
> 
>     Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> 
>     The GENERIC_ISA_DMA option itself was added to arch/sparc/config.in with
>     2.5.31 as:
> 
>         define_bool CONFIG_GENERIC_ISA_DMA y
> 
>     despite of:
> 
>         define_bool CONFIG_ISA n
> "
> 
> The sparc32 code did not differ between ZONE_NORMAL and ZONE_DMA,
> which confirms the above. This patch drop ZONE_DMA.
> 
> Signed-off-by: Sam Ravnborg <sam@...nborg.org>
> Reported-by: "Maciej W. Rozycki" <macro@...am.me.uk>
> Cc: Andreas Larsson <andreas@...sler.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Randy Dunlap <rdunlap@...radead.org>
> Cc: Maciej W. Rozycki <macro@...am.me.uk>
> Cc: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/sparc/Kconfig    | 1 -
>  arch/sparc/mm/srmmu.c | 1 -
>  2 files changed, 2 deletions(-)
> 
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index 734f23daecca..bdbde506c01e 100644
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -62,7 +62,6 @@ config SPARC32
>  	select HAVE_UID16
>  	select LOCK_MM_AND_FIND_VMA
>  	select OLD_SIGACTION
> -	select ZONE_DMA

This however makes a number of PCI drivers that depend on
ZONE_DMA unselectable.

>  
>  config SPARC64
>  	def_bool 64BIT
> diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
> index 852085ada368..7aae2f6f4973 100644
> --- a/arch/sparc/mm/srmmu.c
> +++ b/arch/sparc/mm/srmmu.c
> @@ -975,7 +975,6 @@ void __init srmmu_paging_init(void)
>  	{
>  		unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0 };
>  
> -		max_zone_pfn[ZONE_DMA] = max_low_pfn;
>  		max_zone_pfn[ZONE_NORMAL] = max_low_pfn;
>  		max_zone_pfn[ZONE_HIGHMEM] = highend_pfn;
>  
> 
Thanks,
Andreas