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Message-ID: <BANLkTikhZRb5GWFvTVG0bFjD6rAyJPka1w@mail.gmail.com>
Date: Wed, 22 Jun 2011 13:12:28 +0530
From: Venkatraman S <svenkatr@...com>
To: Per Forlin <per.forlin@...aro.org>
Cc: linaro-dev@...ts.linaro.org,
Nicolas Pitre <nicolas.pitre@...aro.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-mmc@...r.kernel.org, Chris Ball <cjb@...top.org>
Subject: Re: [PATCH v7 01/11] mmc: add non-blocking mmc request function
On Wed, Jun 22, 2011 at 5:08 AM, Per Forlin <per.forlin@...aro.org> wrote:
> Previously there has only been one function mmc_wait_for_req()
> to start and wait for a request. This patch adds
> * mmc_start_req() - starts a request wihtout waiting
> If there is on ongoing request wait for completion
> of that request and start the new one and return.
> Does not wait for the new command to complete.
>
> This patch also adds new function members in struct mmc_host_ops
> only called from core.c
> * pre_req - asks the host driver to prepare for the next job
> * post_req - asks the host driver to clean up after a completed job
>
> The intention is to use pre_req() and post_req() to do cache maintenance
> while a request is active. pre_req() can be called while a request is active
> to minimize latency to start next job. post_req() can be used after the next
> job is started to clean up the request. This will minimize the host driver
> request end latency. post_req() is typically used before ending the block
> request and handing over the buffer to the block layer.
>
> Add a host-private member in mmc_data to be used by
> pre_req to mark the data. The host driver will then
> check this mark to see if the data is prepared or not.
>
> Signed-off-by: Per Forlin <per.forlin@...aro.org>
> ---
> drivers/mmc/core/core.c | 110 +++++++++++++++++++++++++++++++++++++++++----
> include/linux/mmc/core.h | 6 ++-
> include/linux/mmc/host.h | 21 +++++++++
> 3 files changed, 126 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 68091dd..c82fa3b 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -198,9 +198,106 @@ mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
>
> static void mmc_wait_done(struct mmc_request *mrq)
> {
> - complete(mrq->done_data);
> + complete(&mrq->completion);
> }
>
> +static void __mmc_start_req(struct mmc_host *host, struct mmc_request *mrq)
> +{
> + init_completion(&mrq->completion);
> + mrq->done = mmc_wait_done;
> + mmc_start_request(host, mrq);
> +}
> +
> +static void mmc_wait_for_req_done(struct mmc_host *host,
> + struct mmc_request *mrq)
> +{
> + wait_for_completion(&mrq->completion);
> +}
> +
> +/**
> + * mmc_pre_req - Prepare for a new request
> + * @host: MMC host to prepare command
> + * @mrq: MMC request to prepare for
> + * @is_first_req: true if there is no previous started request
> + * that may run in parellel to this call, otherwise false
> + *
> + * mmc_pre_req() is called in prior to mmc_start_req() to let
> + * host prepare for the new request. Preparation of a request may be
> + * performed while another request is running on the host.
> + */
> +static void mmc_pre_req(struct mmc_host *host, struct mmc_request *mrq,
> + bool is_first_req)
> +{
> + if (host->ops->pre_req)
> + host->ops->pre_req(host, mrq, is_first_req);
> +}
> +
> +/**
> + * mmc_post_req - Post process a completed request
> + * @host: MMC host to post process command
> + * @mrq: MMC request to post process for
> + * @err: Error, if non zero, clean up any resources made in pre_req
> + *
> + * Let the host post process a completed request. Post processing of
> + * a request may be performed while another reuqest is running.
> + */
> +static void mmc_post_req(struct mmc_host *host, struct mmc_request *mrq,
> + int err)
> +{
> + if (host->ops->post_req)
> + host->ops->post_req(host, mrq, err);
> +}
> +
> +/**
> + * mmc_start_req - start a non-blocking request
> + * @host: MMC host to start command
> + * @areq: async request to start
> + * @error: out parameter returns 0 for success, otherwise non zero
> + *
> + * Start a new MMC custom command request for a host.
> + * If there is on ongoing async request wait for completion
> + * of that request and start the new one and return.
> + * Does not wait for the new request to complete.
> + *
> + * Returns the completed async request, NULL in case of none completed.
> + */
> +struct mmc_async_req *mmc_start_req(struct mmc_host *host,
> + struct mmc_async_req *areq, int *error)
> +{
> + int err = 0;
> + struct mmc_async_req *data = host->areq;
> +
> + /* Prepare a new request */
> + if (areq)
> + mmc_pre_req(host, areq->mrq, !host->areq);
> +
> + if (host->areq) {
> + mmc_wait_for_req_done(host, host->areq->mrq);
> + err = host->areq->err_check(host->card, host->areq);
> + if (err) {
> + mmc_post_req(host, host->areq->mrq, 0);
> + if (areq)
> + mmc_post_req(host, areq->mrq, -EINVAL);
> +
> + host->areq = NULL;
> + goto out;
In this sequence, would the return value (data) have the previous areq ?
Is that intentional - doesn't seem to fit with the description.
> + }
> + }
> +
> + if (areq)
> + __mmc_start_req(host, areq->mrq);
> +
> + if (host->areq)
> + mmc_post_req(host, host->areq->mrq, 0);
> +
> + host->areq = areq;
> + out:
> + if (error)
> + *error = err;
> + return data;
> +}
> +EXPORT_SYMBOL(mmc_start_req);
> +
--
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