linux-kernel - Re: [PATCH v3 2/3] mmc: Add realtek USB sdmmc host driver

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Message-ID: <52FAECEB.3060902@realtek.com>
Date:	Wed, 12 Feb 2014 11:39:23 +0800
From:	Roger <rogerable@...ltek.com>
To:	Ulf Hansson <ulf.hansson@...aro.org>
CC:	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>, Chris Ball <cjb@...top.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	Alex Dubov <oakad@...oo.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	<driverdev-devel@...uxdriverproject.org>,
	Wei WANG <wei_wang@...lsil.com.cn>,
	<micky_ching@...lsil.com.cn>
Subject: Re: [PATCH v3 2/3] mmc: Add realtek USB sdmmc host driver

On 02/11/2014 05:50 PM, Ulf Hansson wrote:
> On 11 February 2014 10:27, Roger <rogerable@...ltek.com> wrote:
>> On 02/10/2014 10:58 PM, Ulf Hansson wrote:
>>>
>>> On 6 February 2014 15:35,  <rogerable@...ltek.com> wrote:
>>>>
>>>> From: Roger Tseng <rogerable@...ltek.com>
>>>>
>>>> Realtek USB SD/MMC host driver provides mmc host support based on the
>>>> Realtek
>>>> USB card reader MFD driver.
>>>>
>>>> Signed-off-by: Roger Tseng <rogerable@...ltek.com>
>>>> ---
>>>>    drivers/mmc/host/Kconfig          |    7 +
>>>>    drivers/mmc/host/Makefile         |    1 +
>>>>    drivers/mmc/host/rtsx_usb_sdmmc.c | 1500
>>>> +++++++++++++++++++++++++++++++++++++
>>>>    3 files changed, 1508 insertions(+)
>>>>    create mode 100644 drivers/mmc/host/rtsx_usb_sdmmc.c
>>
>> [snip]
>>
>>>> +#ifdef CONFIG_PM_RUNTIME
>>>
>>>
>>> There are stubs for pm_runtime* functions, thus the ifdefs can be removed.
>>> Please go though the complete patch and remove all instances.
>>>
>>>> +               pm_runtime_put(sdmmc_dev(host));
>>>
>>>
>>> I don't know so much about USB mmc hosts hardware, but I just wanted
>>> to find out if I have understood this correct.
>>>
>>> You can't do fine grained power management of the USB parent device,
>>> since it needs to be runtime resumed to be able keep the power the
>>> card? Once it becomes runtime suspended, the power to the card will
>>> thus also be dropped?
>>>
>> Yes, and to keep some internal state of the controller.
>
> Okay.
>
> But the internal state of the controller should be possible to restore
> at runtime_resume, so that should not be the reason, right?
>

I checked again. Internal registers will hold its state during suspend.
Card power is the exact reason.
>>> Kind regards
>>> Ulf Hansson
> .
>
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