linux-kernel - Re: [PATCH] powerpc: enable a 30-bit ZONE

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Date:   Wed, 19 Jun 2019 22:32:24 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christoph Hellwig <hch@....de>, benh@...nel.crashing.org,
        paulus@...ba.org
Cc:     Larry.Finger@...inger.net, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, aaro.koskinen@....fi
Subject: Re: [PATCH] powerpc: enable a 30-bit ZONE_DMA for 32-bit pmac

Christoph Hellwig <hch@....de> writes:
> Any chance this could get picked up to fix the regression?

Was hoping Ben would Ack it. He's still powermac maintainer :)

I guess he OK'ed it in the other thread, will add it to my queue.

cheers

> On Thu, Jun 13, 2019 at 10:24:46AM +0200, Christoph Hellwig wrote:
>> With the strict dma mask checking introduced with the switch to
>> the generic DMA direct code common wifi chips on 32-bit powerbooks
>> stopped working.  Add a 30-bit ZONE_DMA to the 32-bit pmac builds
>> to allow them to reliably allocate dma coherent memory.
>> 
>> Fixes: 65a21b71f948 ("powerpc/dma: remove dma_nommu_dma_supported")
>> Reported-by: Aaro Koskinen <aaro.koskinen@....fi>
>> Signed-off-by: Christoph Hellwig <hch@....de>
>> ---
>>  arch/powerpc/include/asm/page.h         | 7 +++++++
>>  arch/powerpc/mm/mem.c                   | 3 ++-
>>  arch/powerpc/platforms/powermac/Kconfig | 1 +
>>  3 files changed, 10 insertions(+), 1 deletion(-)
>> 
>> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
>> index b8286a2013b4..0d52f57fca04 100644
>> --- a/arch/powerpc/include/asm/page.h
>> +++ b/arch/powerpc/include/asm/page.h
>> @@ -319,6 +319,13 @@ struct vm_area_struct;
>>  #endif /* __ASSEMBLY__ */
>>  #include <asm/slice.h>
>>  
>> +/*
>> + * Allow 30-bit DMA for very limited Broadcom wifi chips on many powerbooks.
>> + */
>> +#ifdef CONFIG_PPC32
>> +#define ARCH_ZONE_DMA_BITS 30
>> +#else
>>  #define ARCH_ZONE_DMA_BITS 31
>> +#endif
>>  
>>  #endif /* _ASM_POWERPC_PAGE_H */
>> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
>> index cba29131bccc..2540d3b2588c 100644
>> --- a/arch/powerpc/mm/mem.c
>> +++ b/arch/powerpc/mm/mem.c
>> @@ -248,7 +248,8 @@ void __init paging_init(void)
>>  	       (long int)((top_of_ram - total_ram) >> 20));
>>  
>>  #ifdef CONFIG_ZONE_DMA
>> -	max_zone_pfns[ZONE_DMA]	= min(max_low_pfn, 0x7fffffffUL >> PAGE_SHIFT);
>> +	max_zone_pfns[ZONE_DMA]	= min(max_low_pfn,
>> +			((1UL << ARCH_ZONE_DMA_BITS) - 1) >> PAGE_SHIFT);
>>  #endif
>>  	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
>>  #ifdef CONFIG_HIGHMEM
>> diff --git a/arch/powerpc/platforms/powermac/Kconfig b/arch/powerpc/platforms/powermac/Kconfig
>> index f834a19ed772..c02d8c503b29 100644
>> --- a/arch/powerpc/platforms/powermac/Kconfig
>> +++ b/arch/powerpc/platforms/powermac/Kconfig
>> @@ -7,6 +7,7 @@ config PPC_PMAC
>>  	select PPC_INDIRECT_PCI if PPC32
>>  	select PPC_MPC106 if PPC32
>>  	select PPC_NATIVE
>> +	select ZONE_DMA if PPC32
>>  	default y
>>  
>>  config PPC_PMAC64
>> -- 
>> 2.20.1
> ---end quoted text---