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

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Date:   Wed, 4 Mar 2020 10:28:28 +0200
From:   Roger Quadros <rogerq@...com>
To:     Rob Herring <robh+dt@...nel.org>,
        Robin Murphy <robin.murphy@....com>
CC:     Christoph Hellwig <hch@....de>,
        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

Hi,

On 03/03/2020 21:26, Rob Herring wrote:
> On Tue, Mar 3, 2020 at 8:06 AM Robin Murphy <robin.murphy@....com> wrote:
>>
>> On 03/03/2020 8:27 am, Roger Quadros wrote:
>> [...]
>>>> With the patch (in the end). dev->bus_dma_limit is still set to 0 and
>>>> so is not being used.
>>>>
>>>> from of_dma_configure()
>>>>           ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
>>>> ...
>>>>           /* ...but only set bus limit if we found valid dma-ranges
>>>> earlier */
>>>>           if (!ret)
>>>>                   dev->bus_dma_limit = end;
>>>>
>>>> There is no other place bus_dma_limit is set. Looks like every device
>>>> should inherit that
>>>> from it's parent right?
>>>
>>> Any ideas how to expect this to work?
>>
>> Is of_dma_get_range() actually succeeding, or is it tripping up on some
>> aspect of the DT (in which case there should be errors in the log)?
>>

of_dma_get_range() was failing but no errors in the log.

>> Looking again at the fragment below, are you sure it's correct? It
>> appears to me like it might actually be defining a 1-byte-long DMA
>> range, which indeed I wouldn't really expect to work.
> 
> Indeed, though it took me a minute to see why.
> 
>>
>> Robin.
>>
>>>>
>>>> diff --git a/arch/arm/boot/dts/dra7.dtsi b/arch/arm/boot/dts/dra7.dtsi
>>>> index 64a0f90f5b52..5418c31d4da7 100644
>>>> --- a/arch/arm/boot/dts/dra7.dtsi
>>>> +++ b/arch/arm/boot/dts/dra7.dtsi
>>>> @@ -680,15 +680,22 @@
>>>>            };
>>>>
>>>>            /* OCP2SCP3 */
>>>> -        sata: sata@...41100 {
>>>> -            compatible = "snps,dwc-ahci";
>>>> -            reg = <0x4a140000 0x1100>, <0x4a141100 0x7>;
> 
> Based on this, the parent address size is 1 cell...
> 
>>>> -            interrupts = <GIC_SPI 49 IRQ_TYPE_LEVEL_HIGH>;
>>>> -            phys = <&sata_phy>;
>>>> -            phy-names = "sata-phy";
>>>> -            clocks = <&l3init_clkctrl DRA7_L3INIT_SATA_CLKCTRL 8>;
>>>> -            ti,hwmods = "sata";
>>>> -            ports-implemented = <0x1>;
>>>> +        sata_aux_bus {
>>>> +            #address-cells = <2>;
>>>> +            #size-cells = <2>;
>>>> +            compatible = "simple-bus";
>>>> +            ranges = <0x0 0x0 0x4a140000 0x0 0x1200>;
>>>> +            dma-ranges = <0x0 0x0 0x0 0x0 0x1 0x00000000>;
> 
> So this is:
> child addr: 0x0 0x0
> parent addr: 0x0
> size: 0x0 0x1

Good catch.
So I fixed it to

	dma-ranges = <0x0 0x0 0x0 0x1 0x00000000>;

And now it works :).
Thanks!

> 
> The last cell is just ignored I guess if you aren't seeing any errors.
> We check this in dtc for ranges, but not dma-ranges. So I'm fixing
> that.

Great!

> 
>>>> +            sata: sata@...41100 {
>>>> +                compatible = "snps,dwc-ahci";
>>>> +                reg = <0x0 0x0 0x0 0x1100>, <0x0 0x1100 0x0 0x7>;
>>>> +                interrupts = <GIC_SPI 49 IRQ_TYPE_LEVEL_HIGH>;
>>>> +                phys = <&sata_phy>;
>>>> +                phy-names = "sata-phy";
>>>> +                clocks = <&l3init_clkctrl DRA7_L3INIT_SATA_CLKCTRL 8>;
>>>> +                ti,hwmods = "sata";
>>>> +                ports-implemented = <0x1>;
>>>> +            };
>>>>            };
>>>>
>>>>            /* OCP2SCP1 */
>>>>
>>>

-- 
cheers,
-roger
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