linux-kernel - Re: [PATCH 2/2] mmc: rtsx: add support for async request

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Message-ID: <539F9412.3010209@realsil.com.cn>
Date:	Tue, 17 Jun 2014 09:04:18 +0800
From:	micky <micky_ching@...lsil.com.cn>
To:	Ulf Hansson <ulf.hansson@...aro.org>
CC:	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Chris Ball <chris@...ntf.net>, <devel@...uxdriverproject.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Roger <rogerable@...ltek.com>, Wei WANG <wei_wang@...lsil.com.cn>
Subject: Re: [PATCH 2/2] mmc: rtsx: add support for async request

On 06/16/2014 08:40 PM, Ulf Hansson wrote:
> On 16 June 2014 11:09, micky <micky_ching@...lsil.com.cn> wrote:
>> On 06/16/2014 04:42 PM, Ulf Hansson wrote:
>>>> @@ -36,7 +37,10 @@ struct realtek_pci_sdmmc {
>>>>>          struct rtsx_pcr         *pcr;
>>>>>          struct mmc_host         *mmc;
>>>>>          struct mmc_request      *mrq;
>>>>> +       struct workqueue_struct *workq;
>>>>> +#define SDMMC_WORKQ_NAME       "rtsx_pci_sdmmc_workq"
>>>>>
>>>>> +       struct work_struct      work;
>>> I am trying to understand why you need a work/workqueue to implement
>>> this feature. Is that really the case?
>>>
>>> Could you elaborate on the reasons?
>> Hi Uffe,
>>
>> we need return as fast as possible in mmc_host_ops request(ops->request)
>> callback,
>> so the mmc core can continue handle next request.
>> when next request everything is ready, it will wait previous done(if not
>> done),
>> then call ops->request().
>>
>> we can't use atomic context, because we use mutex_lock() to protect
> ops->request should never executed in atomic context. Is that your concern?
Yes.
>
>> resource, and we have to hold the lock during handle request.
>> So I use workq, we just queue a work and return in ops->request(),
>> The mmc core can continue without blocking at ops->request().
>>
>> Best Regards.
>> micky.
> Kind regards
> Uffe
> .
>

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