linux-kernel - Re: [PATCH 0/4] MIPS: ath79: Add USB support on the TL-WR1043ND

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Date:	Tue, 29 Sep 2015 16:40:42 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Arnd Bergmann <arnd@...db.de>, Alban <albeu@...e.fr>
CC:	<linux-mips@...ux-mips.org>, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Ralf Baechle <ralf@...ux-mips.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] MIPS: ath79: Add USB support on the TL-WR1043ND

Hi,

On Wednesday 09 September 2015 07:51 PM, Arnd Bergmann wrote:
> On Wednesday 09 September 2015 16:14:59 Alban wrote:
>> On Mon, 07 Sep 2015 15:20:42 +0200
>> Arnd Bergmann <arnd@...db.de> wrote:
>>
>>> On Tuesday 01 September 2015 17:23:10 Alban Bedel wrote:
>>>>
>>>> this serie add a driver for the USB phy on the ATH79 SoCs and enable the
>>>> USB port on the TL-WR1043ND. The phy controller is really trivial as it
>>>> only use reset lines.
>>>>
>>>
>>> Is this a common thing to have? If other PHY devices are like this, we
>>> could instead add a simple generic PHY driver that just asserts all
>>> its reset lines in the order as provided, rather than making this a
>>> hardware specific driver that ends up getting copied several times.
>>
>> I don't know how common it is. However I agree that a simple driver that
>> can start a clock and toggle a few GPIO and/or reset would make sense.
>>
>> However in the case of the ATH79 SoC some models have a reset line that
>> is misused to force the PHY in sleep mode. Sadly this extra reset must
>> be asserted for the PHY to work, so it wouldn't fit in such a generic
>> design.
>>
>> Still we could have such a generic driver and let the ATH79 driver
>> build on top of it. Honestly that's what I wanted to do, but getting
>> generic drivers with DT support accepted is not easy. That's why I went
>> with this driver, it is technically inferior but much easier to get
>> considered for merging.
> 
> Ok, fair enough. If we end up doing a more generic driver for this,
> we can still consider adding the compatible string there, potentially
> with some workaround for the sleep mode.

hmm, makes sense to have a generic PHY driver for PHY's which doesn't
have PHY registers to be programmed like a PHY driver which enables only
clocks, regulators, drives gpios etc.

Cheers
Kishon
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