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Subject: 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, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, iommu@lists.linux-foundation.org,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        paulus@samba.org, darren@stevens-zone.net,
        "contact@a-eon.com" <contact@a-eon.com>, rtd2@xtra.co.nz,
        mad skateman <madskateman@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        nsaenzjulienne@suse.de
References: <F1EBB706-73DF-430E-9020-C214EC8ED5DA@xenosoft.de>
 <20191121072943.GA24024@lst.de>
 <dbde2252-035e-6183-7897-43348e60647e@xenosoft.de>
Message-ID: <6eec5c42-019c-a988-fc2a-cb804194683d@xenosoft.de>
Date:   Thu, 21 Nov 2019 13:21:23 +0100
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On 21 November 2019 at 01:16 pm, Christian Zigotzky wrote:
> On 21 November 2019 at 08:29 am, Christoph Hellwig wrote:
>> On Sat, Nov 16, 2019 at 08:06:05AM +0100, Christian Zigotzky wrote:
>>> /*
>>>   *  DMA addressing mode.
>>>   *
>>>   *  0 : 32 bit addressing for all chips.
>>>   *  1 : 40 bit addressing when supported by chip.
>>>   *  2 : 64 bit addressing when supported by chip,
>>>   *      limited to 16 segments of 4 GB -> 64 GB max.
>>>   */
>>> #define   SYM_CONF_DMA_ADDRESSING_MODE 
>>> CONFIG_SCSI_SYM53C8XX_DMA_ADDRESSING_MODE
>>>
>>> Cyrus config:
>>>
>>> CONFIG_SCSI_SYM53C8XX_DMA_ADDRESSING_MODE=1
>>>
>>> I will configure “0 : 32 bit addressing for all chips” for the RC8. 
>>> Maybe this is the solution.
>> 0 means you are going to do bounce buffering a lot, which seems
>> generally like a bad idea.
>>
>> But why are we talking about the sym53c8xx driver now?  The last issue
>> you reported was about video4linux allocations.
>>
> Both drivers have the same problem. They don't work if we have more 
> than 3.5GB RAM. I try to find a solution until you have a good 
> solution. I have already a solution for V4L but I still need one for 
> the sym53c8xx driver.
OK, you mean that "0" is a bad idea but maybe it works until you have a 
solution. ;-)