linux-kernel - Re: [PATCH] serial: samsung: Fix serial config dependencies for exynos7

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Message-ID: <CAM4voam9jEuYvwDUnAZzU4Q-aZdF-P+KUuSm=x-9beobpyeR1w@mail.gmail.com>
Date:	Tue, 30 Sep 2014 20:02:22 +0530
From:	Abhilash Kesavan <kesavan.abhilash@...il.com>
To:	Tomasz Figa <tomasz.figa@...il.com>
Cc:	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	jslaby@...e.cz, Pankaj Dubey <pankaj.dubey@...sung.com>
Subject: Re: [PATCH] serial: samsung: Fix serial config dependencies for exynos7

Hi Tomasz,

On Tue, Sep 30, 2014 at 4:08 AM, Tomasz Figa <tomasz.figa@...il.com> wrote:
> Hi Abhilash,
>
> The patch itself seems fine, but I wonder if those config options aren't
> really just leftovers from the past and couldn't be completely removed.
>
> On 29.09.2014 07:16, Abhilash Kesavan wrote:
>> From: Pankaj Dubey <pankaj.dubey@...sung.com>
>>
>> Exynos7 has a similar serial controller to that present in older Samsung
>> SoCs. To re-use the existing serial driver on Exynos7 we need to have
>> SERIAL_SAMSUNG_UARTS_4 and SERIAL_SAMSUNG_UARTS selected. This is not
>> possible because these symbols are dependent on PLAT_SAMSUNG which is
>> not present for the ARMv8 based exynos7.
>>
>> Change the dependency of these symbols from PLAT_SAMSUNG to the serial
>> driver thus making it available on exynos7. As the existing platform
>> specific code making use of these symbols is related to uart driver this
>> change in dependency should not cause any issues.
>>
>> Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
>> Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@...sung.com>
>> Signed-off-by: Abhilash Kesavan <a.kesavan@...sung.com>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> ---
>> Build tested with s3c6400_defconfig, exynos_defconfig and arm64's defconfig
>> with and without the serial driver enabled.
>>
>>  drivers/tty/serial/Kconfig |    4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
>> index 81f6ee7..e6c0bcb 100644
>> --- a/drivers/tty/serial/Kconfig
>> +++ b/drivers/tty/serial/Kconfig
>> @@ -249,14 +249,14 @@ config SERIAL_SAMSUNG
>>
>>  config SERIAL_SAMSUNG_UARTS_4
>>       bool
>> -     depends on PLAT_SAMSUNG
>> +     depends on SERIAL_SAMSUNG
>>       default y if !(CPU_S3C2410 || CPU_S3C2412 || CPU_S3C2440 || CPU_S3C2442)
>>       help
>>         Internal node for the common case of 4 Samsung compatible UARTs
>
> The only place where this symbol is used is below.
>
>>
>>  config SERIAL_SAMSUNG_UARTS
>>       int
>> -     depends on PLAT_SAMSUNG
>> +     depends on SERIAL_SAMSUNG
>>       default 4 if SERIAL_SAMSUNG_UARTS_4 || CPU_S3C2416
>>       default 3
>>       help
>>
>
> With this symbol the situation isn't that easy, but still should be
> manageable.
>
> Looking at the serial-samsung driver, all occurrences of
> CONFIG_SERIAL_SAMSUNG_UARTS could be simply replaced with a locally
> defined number equal to the maximum value - in this case 4.
>
> There are also two places in arch/arm where this symbol is used:
>
> 1) In arch/arm/mach-s3c64xx/irq-pm.c it's used as the number of serial
> ports which need suspend/resume handling. Since on s3c64xx the number is
> always 4, it can be simply defined locally as a constant.
>
> 2) In arch/arm/plat-samsung/init.c it is used to determine size of a
> static array of UART ports and to check whether the UART driver is
> enabled. In former case I believe it should be safe to hardcode it to 4
> as well, in latter CONFIG_SERIAL_SAMSUNG can be used.

I will post patches removing these two symbols.

Regards,
Abhilash
>
> Best regards,
> Tomasz
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