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Subject: Re: [PATCH kernel v3 0/3] powerpc/ioda2: Yet another attempt to allow
 DMA masks between 32 and 59
To: Alexey Kardashevskiy <aik@ozlabs.ru>, linuxppc-dev@lists.ozlabs.org
References: <20190530070355.121802-1-aik@ozlabs.ru>
From: Shawn Anastasio <shawn@anastas.io>
Message-ID: <deb34b5f-9472-2156-e58d-8dbcb0a38979@anastas.io>
Date: Wed, 5 Jun 2019 23:11:06 -0500
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Cc: Sam Bobroff <sbobroff@linux.ibm.com>,
 Alistair Popple <alistair@popple.id.au>, Oliver O'Halloran <oohall@gmail.com>,
 David Gibson <david@gibson.dropbear.id.au>
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On 5/30/19 2:03 AM, Alexey Kardashevskiy wrote:
> This is an attempt to allow DMA masks between 32..59 which are not large
> enough to use either a PHB3 bypass mode or a sketchy bypass. Depending
> on the max order, up to 40 is usually available.
> 
> 
> This is based on v5.2-rc2.
> 
> Please comment. Thanks.

I have tested this patch set with an AMD GPU that's limited to <64bit
DMA (I believe it's 40 or 42 bit). It successfully allows the card to
operate without falling back to 32-bit DMA mode as it does without
the patches.

Relevant kernel log message:
```
[    0.311211] pci 0033:01     : [PE# 00] Enabling 64-bit DMA bypass
```

Tested-by: Shawn Anastasio <shawn@anastas.io>