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

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Message-ID: <CAPDyKFqKDAqvacwCVKM8KLjxfykpBq38MS_RgWCcA7+He4_S5w@mail.gmail.com>
Date:	Mon, 16 Jun 2014 14:40:09 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	micky <micky_ching@...lsil.com.cn>
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 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?

> 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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