linux-kernel - Re: dma_mask limited to 32-bits with OF platform device

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Date:   Wed, 19 Feb 2020 16:29:20 +0200
From:   Roger Quadros <rogerq@...com>
To:     Rob Herring <robh+dt@...nel.org>
CC:     Christoph Hellwig <hch@....de>,
        Robin Murphy <robin.murphy@....com>,
        Péter Ujfalusi <peter.ujfalusi@...com>,
        Murali Karicheri <m-karicheri2@...com>,
        "Nori, Sekhar" <nsekhar@...com>, "Anna, Suman" <s-anna@...com>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Andreas Färber <afaerber@...e.de>,
        Hans Verkuil <hverkuil@...all.nl>,
        <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Nishanth Menon <nm@...com>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        Vignesh Raghavendra <vigneshr@...com>
Subject: Re: dma_mask limited to 32-bits with OF platform device

Rob,

On 18/02/2020 19:22, Rob Herring wrote:
> On Tue, Feb 18, 2020 at 2:28 AM Roger Quadros <rogerq@...com> wrote:
>>
>> Chrishtoph,
>>
>> The branch works fine for SATA on DRA7 with CONFIG_LPAE once I
>> have the below DT fix.
>>
>> Do you intend to send these fixes to -stable?
>>
>> ------------------------- arch/arm/boot/dts/dra7.dtsi -------------------------
>> index d78b684e7fca..853ecf3cfb37 100644
>> @@ -645,6 +645,8 @@
>>                  sata: sata@...41100 {
>>                          compatible = "snps,dwc-ahci";
>>                          reg = <0x4a140000 0x1100>, <0x4a141100 0x7>;
>> +                       #size-cells = <2>;
>> +                       dma-ranges = <0x00000000 0x00000000 0x1 0x00000000>;
> 
> dma-ranges should be in the parent (bus) node, not the device node.

I didn't understand why.

There are many devices on the parent bus node and all devices might not have the 32-bit DMA limit
the SATA controller has.

SATA controller is the bus master and the ATA devices are children of the SATA controller.

 From Documentation/devicetree/booting-without-of.txt

* DMA Bus master
Optional property:
- dma-ranges: <prop-encoded-array> encoded as arbitrary number of triplets of
         (child-bus-address, parent-bus-address, length). Each triplet specified
         describes a contiguous DMA address range.
         The dma-ranges property is used to describe the direct memory access (DMA)
         structure of a memory-mapped bus whose device tree parent can be accessed
         from DMA operations originating from the bus. It provides a means of
         defining a mapping or translation between the physical address space of
         the bus and the physical address space of the parent of the bus.
         (for more information see the Devicetree Specification)

* DMA Bus child
Optional property:
- dma-ranges: <empty> value. if present - It means that DMA addresses
         translation has to be enabled for this device.
- dma-coherent: Present if dma operations are coherent



> 
>>                          interrupts = <GIC_SPI 49 IRQ_TYPE_LEVEL_HIGH>;
>>                          phys = <&sata_phy>;
>>                          phy-names = "sata-phy";
>>
>>
>> cheers,
>> -roger
>>
>> On 17/02/2020 15:21, Christoph Hellwig wrote:
>>> Roger,
>>>
>>> can you try the branch below and check if that helps?
>>>
>>>       git://git.infradead.org/users/hch/misc.git arm-dma-bus-limit
>>>
>>> Gitweb:
>>>
>>>       http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/arm-dma-bus-limit
>>>
>>
>> --
>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

-- 
cheers,
-roger
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki