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

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Message-ID: <539EB43B.8070707@realsil.com.cn>
Date:	Mon, 16 Jun 2014 17:09:15 +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 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
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.
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