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Message-ID: <BANLkTi=TY3wrH2GH1B2p+L506aUKOjg9uA@mail.gmail.com>
Date: Wed, 22 Jun 2011 10:45:16 +0200
From: Per Forlin <per.forlin@...aro.org>
To: Venkatraman S <svenkatr@...com>
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 22 June 2011 09:42, Venkatraman S <svenkatr@...com> wrote:
> 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.
It will return the data that belongs to the completed request. The
completed request will be the same as the previous request. The
mmc_start_req will start a new request and return data for the
completed request, if any.
Do you think I should clarify the description?
Regards,
Per
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