Re: Bug 205201 - Booting halts if Dawicontrol DC-2976 UW SCSI board installed, unless RAM size limited to 3500M

From: Christian Zigotzky <chzigotzky@xenosoft.de>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-arch@vger.kernel.org, darren@stevens-zone.net,
	rtd2@xtra.co.nz,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	linux-kernel@vger.kernel.org, Mike Rapoport <rppt@linux.ibm.com>,
	linux-mm@kvack.org, iommu@lists.linux-foundation.org,
	Rob Herring <robh+dt@kernel.org>,
	paulus@samba.org, mad skateman <madskateman@gmail.com>,
	"contact@a-eon.com" <contact@a-eon.com>,
	Robin Murphy <robin.murphy@arm.com>,
	nsaenzjulienne@suse.de
Subject: Re: Bug 205201 - Booting halts if Dawicontrol DC-2976 UW SCSI board installed, unless RAM size limited to 3500M
Date: Tue, 26 Nov 2019 12:26:38 +0100	[thread overview]
Message-ID: <4681f5fe-c095-15f5-9221-4b55e940bafc@xenosoft.de> (raw)
In-Reply-To: <20191125073923.GA30168@lst.de>

On 25 November 2019 at 08:39 am, Christoph Hellwig wrote:
> On Sat, Nov 23, 2019 at 12:42:27PM +0100, Christian Zigotzky wrote:
>> Hello Christoph,
>>
>> Please find attached the dmesg of your Git kernel.
> Thanks.  It looks like on your platform the swiotlb buffer isn't
> actually addressable based on the bus dma mask limit, which is rather
> interesting.  swiotlb_init uses memblock_alloc_low to allocate the
> buffer, and I'll need some help from Mike and the powerpc maintainers
> to figure out how that select where to allocate the buffer from, and
> how we can move it to a lower address.  My gut feeling would be to try
> to do what arm64 does and define a new ARCH_LOW_ADDRESS_LIMIT, preferably
> without needing too much arch specific magic.
>
> As a quick hack can you try this patch on top of the tree from Friday?
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index f491690d54c6..e3f95c362922 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -344,7 +344,7 @@ static inline int memblock_get_region_node(const struct memblock_region *r)
>   #define MEMBLOCK_LOW_LIMIT 0
>   
>   #ifndef ARCH_LOW_ADDRESS_LIMIT
> -#define ARCH_LOW_ADDRESS_LIMIT  0xffffffffUL
> +#define ARCH_LOW_ADDRESS_LIMIT  0x0fffffffUL
>   #endif
>   
>   phys_addr_t memblock_phys_alloc_range(phys_addr_t size, phys_addr_t align,
>
Hello Christoph,

The PCI TV card works with your patch! I was able to patch your Git 
kernel with the patch above.

I haven't found any error messages in the dmesg yet.

Thank you!

Cheers,
Christian
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