Re: [PATCH v2 1/3] clk: meson: add DT documentation for emmc clock controller

From: Yixun Lan <yixun.lan@amlogic.com>
To: Kevin Hilman <khilman@baylibre.com>
Cc: yixun.lan@amlogic.com, "Rob Herring" <robh@kernel.org>,
	"Jerome Brunet" <jbrunet@baylibre.com>,
	"Neil Armstrong" <narmstrong@baylibre.com>,
	"Carlo Caione" <carlo@caione.org>,
	"Michael Turquette" <mturquette@baylibre.com>,
	"Stephen Boyd" <sboyd@kernel.org>,
	"Miquèl Raynal" <miquel.raynal@bootlin.com>,
	"Boris Brezillon" <boris.brezillon@bootlin.com>,
	"Martin Blumenstingl" <martin.blumenstingl@googlemail.com>,
	"Liang Yang" <liang.yang@amlogic.com>,
	"Qiufang Dai" <qiufang.dai@amlogic.com>,
	"Jian Hu" <jian.hu@amlogic.com>,
	linux-clk <linux-clk@vger.kernel.org>,
	linux-amlogic@lists.infradead.org,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	devicetree@vger.kernel.org
Subject: Re: [PATCH v2 1/3] clk: meson: add DT documentation for emmc clock controller
Date: Mon, 23 Jul 2018 22:28:36 +0800	[thread overview]
Message-ID: <405ff057-a14e-f9eb-19e0-8d467dda35a1@amlogic.com> (raw)
In-Reply-To: <7hbmay3ut6.fsf@baylibre.com>

HI Kevin

On 07/23/2018 10:12 PM, Kevin Hilman wrote:
> Yixun Lan <yixun.lan@amlogic.com> writes:
> 
> [...]
> 
>>>
>>>> Second, we might like to convert eMMC driver to also use mmc-clkc model.
>>>
>>> IMO, this should be done as part of merging this series. Otherwise, we
>>> have duplicated code for the same thing.
>>
>> IMO, I'd leave this out of this series, since this patch series is quite
>> complete as itself. Although, the downside is code duplication.
>>
>> Still, I need to hear Jerome, or Kevin's option, to see if or how we
>> should proceed the eMMC's clock conversion.
>>
>> I could think of three option myself
>> 1) don't do the conversion, downside is code duplication, upside is NO
>> DT change, no compatibility issue
>> 2) add a syscon node into eMMC DT node, then only convert clock part
>> into this mmc-clkc model, while still leave other eMMC register access
>> as the usual iomap way (still no race condition)
>> 3) convert all eMMC register access by using regmap interface.
>>
>> both 2) and 3) need to update the DT.
>>
>> and probably 2) is a compromise way, and 1) is also OK, 3) is probably
>> the worst way due to dramatically change (I think this was already
>> rejected in the previous discussion)
> 
> Because the devices (NAND and eMMC_C) are mutually exclusive, taking the
> step-by-step approach is fine (and preferred) by me.
> 
> Phase 1:
> - add new mmc-clk provider
> - add NAND driver using new mmc-clk provider
> - boards using NAND should ensure emmc_c is disabled in DT
> 
> This allows us to not touch the MMC driver or existing upstream
> bindings.  Yes, this means there is duplicate code in the MMC driver and
> the new mmc-clk provider, but that can be removed in the next phase.
> 
Great, the approach to address this issue is reasonable.
We'd like to focus on phase 1 first, thanks

> Phase 2:
> - convert MMC driver to use new mmc-clk provider
> - update MMC users in DT and bindings
> 
Ok.


Yixun