linux-kernel - Re: [PATCH v2] ARM: dts: dra7: Add bus_dma

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Date:   Mon, 16 Mar 2020 10:35:05 +0200
From:   Roger Quadros <rogerq@...com>
To:     Tony Lindgren <tony@...mide.com>,
        Robin Murphy <robin.murphy@....com>
CC:     <hch@....de>, <robh+dt@...nel.org>, <nm@...com>, <t-kristo@...com>,
        <nsekhar@...com>, <linux-omap@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <stable@...nel.org>
Subject: Re: [PATCH v2] ARM: dts: dra7: Add bus_dma_limit for L3 bus



On 13/03/2020 17:15, Tony Lindgren wrote:
> * Robin Murphy <robin.murphy@....com> [200313 15:06]:
>> On 2020-03-13 9:47 am, Roger Quadros wrote:
>>> The L3 interconnect's memory map is from 0x0 to
>>> 0xffffffff. Out of this, System memory (SDRAM) can be
>>> accessed from 0x80000000 to 0xffffffff (2GB)
>>>
>>> DRA7 does support 4GB of SDRAM but upper 2GB can only be
>>> accessed by the MPU subsystem.
>>>
>>> Add the dma-ranges property to reflect the physical address limit
>>> of the L3 bus.
>>>
>>> Issues ere observed only with SATA on DRA7-EVM with 4GB RAM
>>> and CONFIG_ARM_LPAE enabled. This is because the controller
>>> supports 64-bit DMA and its driver sets the dma_mask to 64-bit
>>> thus resulting in DMA accesses beyond L3 limit of 2G.
>>>
>>> Setting the correct bus_dma_limit fixes the issue.
>>
>> Neat! In principle you should no longer need the specific dma-ranges on the
>> PCIe nodes, since AIUI those really only represent a subset of this general
>> limitation, but given the other inheritance issue you saw it's probably
>> safer to leave them as-is for now.
> 
> Also, Roger, I think omap5 needs a similar patch too, right?
> At least pyra has omap5 with 4GB and SATA connector.

Yes Tony, I'll send a patch for omap5 as well.

> 
>> FWIW,
>>
>> Reviewed-by: Robin Murphy <robin.murphy@....com>
> 
> Sorry missed that as I just pushed out the fix.
> 
> Regards,
> 
> Tony
> 

-- 
cheers,
-roger
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
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