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

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 06/17/2014 03:45 PM, Ulf Hansson wrote:
On 17 June 2014 03:04, micky <micky_ching@xxxxxxxxxxxxxx> wrote:
On 06/16/2014 08:40 PM, Ulf Hansson wrote:
On 16 June 2014 11:09, micky <micky_ching@xxxxxxxxxxxxxx> 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?
Yes.
Okay. Unless I missed your point, I don't think you need the work/workqueue.
any other method?
Because, ops->request isn't ever executed in atomic context. That's
due to the mmc core, which handles the async mechanism, are waiting
for a completion variable in process context, before it invokes the
ops->request() callback.

That completion variable will be kicked, from your host driver, when
you invoke mmc_request_done(), .
Sorry, I don't understand here, how kicked?

I think the flow is:
- not wait for first req
- init mrq->done
- ops->request() --- A.rtsx: start queue work.
- continue fetch next req
- prepare next req ok,
- wait previous done. --- B.(mmc_request_done() may be called at any time from A to B)
- init mrq->done
- ops->request() --- C.rtsx: start queue next work.
...
and seems no problem.

Best Regards.
micky.
Kind regards
Uffe

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
.

.

--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux USB Devel]     [Linux Media]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux