linux-kernel - Re: [RFC PATCH 6/7] mmc: sdhci-omap: Add OMAP SDHCI driver

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Message-ID: <946e5930-7897-5f66-8d75-c112202857d1@ti.com>
Date:   Sun, 20 Aug 2017 16:33:19 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Tony Lindgren <tony@...mide.com>,
        Rob Herring <robh+dt@...nel.org>
CC:     <nsekhar@...com>, <linux-omap@...r.kernel.org>,
        <linux-mmc@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 6/7] mmc: sdhci-omap: Add OMAP SDHCI driver

Adrian,

On Thursday 17 August 2017 01:53 PM, Adrian Hunter wrote:
> On 17/08/17 10:59, Kishon Vijay Abraham I wrote:
>> Hi Adrian,
>>
>> On Thursday 17 August 2017 12:13 PM, Adrian Hunter wrote:
>>> On 17/08/17 08:57, Kishon Vijay Abraham I wrote:
>>>> Hi Adrian,
>>>>
>>>> On Tuesday 15 August 2017 01:52 PM, Adrian Hunter wrote:
>>>>> On 07/08/17 19:01, Kishon Vijay Abraham I wrote:
> 
> <SNIP>
> 
>>>>>> +	pm_runtime_enable(dev);
>>>>>> +	ret = pm_runtime_get_sync(dev);
>>>>>
>>>>> What are you trying to do with runtime pm?  There don't seem to be any pm
>>>>> callbacks, so does this do anything?
>>>>
>>>> yeah, pm_runtime_get_sync enables the functional clock and also configures the
>>>> SYSCONFIG regiters present in the controller. It gets the details for
>>>> configuring those from arch/arm/mach-omap2/omap_hwmod_*
>>>
>>> You mean it will do those things when you add the callbacks?  I would prefer
>>> you leave out runtime pm until you can add the callbacks as well.
>>
>> No. Generally in callbacks, 'optional' functional clocks are enabled. But main
>> functional clock and interface clocks are enabled in pm_runtime_get_sync.
>> Without pm_runtime_get_sync, we won't be able to access controller registers.
> 
> So that is done by the pm domain?  Please add comments to the code to explain.

right, it's done by omap_device_pm_domain.
Invoking pm_runtime_get_sync of a platform device in OMAP platforms will
eventually come to omap_hwmod_enable where main functional clock, interface
clock and sysconfig are programmed.

Thanks
Kishon