On 22 June 2011 10:53, S, Venkatraman [off-list ref] wrote:

On Wed, Jun 22, 2011 at 2:15 PM, Per Forlin [off-list ref] wrote:

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On 22 June 2011 09:42, Venkatraman S [off-list ref] wrote:

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On Wed, Jun 22, 2011 at 5:08 AM, Per Forlin [off-list ref] wrote:

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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 <redacted>
---
?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.

I meant that in case of an error (err !=0), data is already assigned
to host->areq
and goto out returns 'data'. So my question was 'Does returning a non-null
pointer for a unsuccessful request doesn't fit with the description, does it ?'

Now I get it. Thanks for your patience :)

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+       struct mmc_async_req *data = host->areq;

...

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+               mmc_wait_for_req_done(host, host->areq->mrq);
+               err = host->areq->err_check(host->card, host->areq);

in case of error host->areq is returned. Basically the failing request
is returned.
block.c needs the failing request in order to do error handling.

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+ *     @error: out parameter returns 0 for success, otherwise non zero

This parameter indicates error.

Returning NULL is not error. NULL is returned when starting a new
request and there is no ongoing (previous) request.

Regards,
Per