linux-kernel - Re: [PATCH] arm64: dts: stingray: use NUM_SATA to configure number of sata ports

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Message-ID: <0bf3c57c-dac8-8ece-6b8a-3b4d024140fc@broadcom.com>
Date:   Wed, 13 Jun 2018 13:18:35 -0700
From:   Scott Branden <scott.branden@...adcom.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>, Ray Jui <rjui@...adcom.com>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        devicetree@...r.kernel.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: stingray: use NUM_SATA to configure number of
 sata ports

Hi Rob,

Thanks for comment - reply inline.


On 18-06-13 12:31 PM, Florian Fainelli wrote:
> On 06/12/2018 03:54 PM, Rob Herring wrote:
>> On Thu, Jun 7, 2018 at 12:53 PM, Scott Branden
>> <scott.branden@...adcom.com> wrote:
>>> Hi Rob,
>>>
>>> Could you please kindly comment on change below.
>>>
>>> It allows board variants to be added easily via a simple define for
>>> different number of SATA ports.
>>>
>>>
>>>
>>> On 18-06-04 09:22 AM, Florian Fainelli wrote:
>>>> On 05/18/2018 11:34 AM, Scott Branden wrote:
>>>>> Move remaining sata configuration to stingray-sata.dtsi and enable
>>>>> ports based on NUM_SATA defined.
>>>>> Now, all that needs to be done is define NUM_SATA per board.
>>>> Rob could you review this and let us know if this approach is okay or
>>>> not? Thank you!
>>>>
>>>>> Signed-off-by: Scott Branden <scott.branden@...adcom.com>
>>>>> ---
>>>>> diff --git a/arch/arm64/boot/dts/broadcom/stingray/stingray-sata.dtsi
>>>>> b/arch/arm64/boot/dts/broadcom/stingray/stingray-sata.dtsi
>>>>> index 8c68e0c..7f6d176 100644
>>>>> --- a/arch/arm64/boot/dts/broadcom/stingray/stingray-sata.dtsi
>>>>> +++ b/arch/arm64/boot/dts/broadcom/stingray/stingray-sata.dtsi
>>>>> @@ -43,7 +43,11 @@
>>>>>                          interrupts = <GIC_SPI 321 IRQ_TYPE_LEVEL_HIGH>;
>>>>>                          #address-cells = <1>;
>>>>>                          #size-cells = <0>;
>>>>> +#if (NUM_SATA > 0)
>>>>> +                       status = "okay";
>>>>> +#else
>>>>>                          status = "disabled";
>>>>> +#endif
>> This only works if ports are contiguously enabled (0-N). You might not
>> care, but it is not a pattern that works in general.
Correct - all board designs that include this dtsi file follow such 
commonality (ie. design with SATA0 first, etc).  By having common board 
designs it allows for commonality in dts files rather than duplicating 
information everywhere.  If somebody designs a bizarro board they are 
free to create their own dts file of course.
>>   And I'm not a fan
>> of C preprocessing in DT files in general beyond just defines for
>> single numbers.
The use of a define to specify the number of SATA ports in the board 
design meets our requirements of being able to maintain many boards.  We 
need a method to specify the number of ports in the board design rather 
than copying and pasting the information in many dts files.  If you have 
an alternative upstreamable mechanism to manage the configuration of 
many boards without copy and paste that would be ideal?
> Should we interpret this as a formal NAK?