> -----Original Message----- > From: Ulf Hansson [mailto:ulf.hansson@xxxxxxxxxx] > Sent: Monday, March 16, 2015 3:35 PM > To: Alex Lemberg > Cc: Avi Shchislowski; linux-mmc; Chris Ball > Subject: Re: [PATCH] mmc: sleep notification > > On 16 March 2015 at 12:37, Alex Lemberg <Alex.Lemberg@xxxxxxxxxxx> > wrote: > > Hi Ulf, > > > >> -----Original Message----- > >> From: Ulf Hansson [mailto:ulf.hansson@xxxxxxxxxx] > >> Sent: Thursday, March 12, 2015 11:10 AM > >> To: Alex Lemberg > >> Cc: Avi Shchislowski; linux-mmc; Chris Ball > >> Subject: Re: [PATCH] mmc: sleep notification > >> > >> [...] > >> > >> >> > Also, I think we need to clarify one more point for this patch: > >> >> > As was mentioned in commit message - Sleep_Notification can be > >> >> > interrupted > >> >> by HPI. > >> >> > This allows not blocking the host during the Sleep_Notification > >> >> > busy time and allows accepting requests coming during this stage. > >> >> > Thus, without having HPI supported, suspend/resume process might > >> >> > be influenced by Sleep_Notification busy time, and this should > >> >> > not happen - > >> >> suspend/resume should be done in very fast and not blocking manner. > >> >> > >> >> I fail to understand your comment here. > >> >> > >> >> Please tell me at what point(s) your think it make sense to issue > >> >> the SLEEP_NOTIFICATION? If that is during the suspend phase, then > >> >> a HPI request can't be triggered. > >> > > >> > I think SLEEP_NOTIFICATION should be issued on mmc_pm_notify() > >> > call, on PM_SUSPEND_PREPARE case. > >> > >> So, exactly why is that to prefer, comparing doing it in system PM > >> ->suspend() callback? > > > > Assuming that SLEEP_NOTIFICATION may take time (defined in > > SLEEP_NOTIFICATION_TIME byte in EXT_CSD [216]), I think it is better > > to send it from pm notifier - mmc_pm_notify(). > > I assume you think that you will "earn" some milliseconds doing it in this phase, > but I am not so sure. I was thinking mainly about how to prevent "blocking" during Sleep_Notification process. > > After the PM_SUSPEND_PREPARE notifier, we still have the mmc block queue > open and are ready to serve requests. Therefore I would expect the > SLEEP_NOTIFICATION to potentially be interrupted by using HPI. Right, and this was a reason for adding HPI support during the Sleep_Notification. > > Then we end up with the following sequence during the system PM sleep phase. > 1. Issue SLEEP_NOTIFICATION. > 2. Interrupt SLEEP_NOTIFICATION, using HPI. > 3. Serve blk request > 4. Issue SLEEP_NOTIFICATION. > 5. Issue SLEEP (CMD5). Correct, this is a sequence that we see after adding the patch. > That seems like a bad idea to me. Could you please explain why? Would you suggest to call Sleep_Notification from Suspend only? What if Sleep_Notification will take several seconds? > > Kind regards > Uffe ��.n��������+%������w��{.n�����{��i��)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
