linux-kernel - Re: [PATCH] mfd: Add support for CPLD chip on Mikrotik RB4xx boards

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Message-ID: <5523FC32.3080904@biot.com>
Date:	Tue, 07 Apr 2015 17:48:02 +0200
From:	Bert Vermeulen <bert@...t.com>
To:	Lee Jones <lee.jones@...aro.org>
CC:	ralf@...ux-mips.org, sameo@...ux.intel.com,
	linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mfd: Add support for CPLD chip on Mikrotik RB4xx boards

On 07/04/15 08:52, Lee Jones wrote:
> On Mon, 06 Apr 2015, Bert Vermeulen wrote:
>
>> The SPI-connected CPLD chip controls access to the main NAND flash
>> chip and five LEDs.
>>
>> Signed-off-by: Bert Vermeulen <bert@...t.com>
>> ---
>>   arch/mips/include/asm/mach-ath79/rb4xx_cpld.h |  49 +++++
>>   drivers/mfd/Kconfig                           |   7 +
>>   drivers/mfd/Makefile                          |   1 +
>>   drivers/mfd/rb4xx-cpld.c                      | 279 ++++++++++++++++++++++++++
>>   4 files changed, 336 insertions(+)
>>   create mode 100644 arch/mips/include/asm/mach-ath79/rb4xx_cpld.h
>>   create mode 100644 drivers/mfd/rb4xx-cpld.c
>
> This device doesn't look like an MFD, it rather looks like a CPLD
> driver.  We had a recent submission like this [1], perhaps this will
> provide another argument for drivers/programmables or something.
>
> [1] https://lkml.org/lkml/2015/2/17/42

Yup, got bounced into drivers/mfd after initially submitting it as an SPI
protocol driver (where it lives in openwrt). Indeed it's not a great fit
anywhere -- not even programmables: this thing has its firmware on board,
nothing ever feeds it on startup.

Drivers for CPLDs don't necessarily have anything in common -- these are
customized chips basically. In this case it's a NAND controller and GPIO/LED
expander rolled into one.


-- 
Bert Vermeulen
bert@...t.com
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