linux-kernel - Re: [PATCH] gpio: thunderx: select IRQ_DOMAIN

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Message-ID: <CAK7LNAQ9kjUKFL6+Hm+XjQvUDTp6aeeCLQJcgin=Fs446cdQRw@mail.gmail.com>
Date:   Thu, 7 Sep 2017 10:03:51 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     David Daney <ddaney@...iumnetworks.com>
Cc:     linux-gpio@...r.kernel.org, David Daney <david.daney@...ium.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: thunderx: select IRQ_DOMAIN_HIERARCHY instead of
 depends on

Hi David,


2017-09-07 2:36 GMT+09:00 David Daney <ddaney@...iumnetworks.com>:
> On 09/05/2017 09:20 PM, Masahiro Yamada wrote:
>>
>> Hi David,
>>
>>
>> 2017-09-06 11:09 GMT+09:00 David Daney <ddaney@...iumnetworks.com>:
>>>
>>> On 09/05/2017 06:40 PM, Masahiro Yamada wrote:
>>>>
>>>>
>>>> IRQ_DOMAIN_HIERARCHY is not user-configurable, but supposed to be
>>>> selected by drivers that need IRQ domain hierarchy support.
>>>>
>>>> GPIO_THUNDERX is the only user of "depends on IRQ_DOMAIN_HIERARCHY".
>>>> This means, we can not enable GPIO_THUNDERX unless other drivers
>>>> select IRQ_DOMAIN_HIERARCHY elsewhere.  This is odd.  Flip the logic.
>>>>
>>>> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
>>>
>>>
>>>
>>> IRQ_DOMAIN_HIERARCHY is set as a result of ARCH_THUNDER (this SoC
>>> hardware),
>>> so it actually works as-is.
>>
>>
>>
>> Right, ARCH_THUNDER does not select it directly,
>> but does it indirectly.  (this is not so clear...)
>>
>> ARCH_THUNDER  -> ARM64 -> ARM_GIC -> IRQ_DOMAIN_HIERARCHY
>>
>>
>>
>>>   That said, this looks like a reasonable
>>> improvement, and will allow the COMPILE_TEST to enable it, so...
>>>
>>> Acked-by: David Daney <david.daney@...ium.com>
>>
>>
>>
>> BTW, I could not understand your intention of
>> (64BIT && COMPILE_TEST)
>>
>
> The driver uses readq()/writeq(), which are not available in some 32BIT
> kernels.  So to ensure that it can build without error we depend on 64BIT as
> a proxy for the availability of readq()/writeq()
>
>


IMHO, drivers code should not depend on CPU architecture too much.


Does the following make sense for your driver?


- split {read,write}q into two transactions of {read,write}l

or

- include <linux/io-64-nonatomic-hi-lo.h> or
          <linux-io-64-nonatomic-lo-hi.h>
   (choose a suitable one for your driver)




-- 
Best Regards
Masahiro Yamada