On Fri, Aug 14, 2015 at 1:24 AM, Yao Yuan <yao.yuan@xxxxxxxxxxxxx> wrote: > Hi Leo, > > Thanks for your review. > About those two methods for DMA suspend that you have mentioned. We have a lot of the discussions in other DMA driver like DMA for Freescale PowerPC. > > Finally, we think the device which used the DMA transmission service should cancel the transmission service in its suspend. > So DMA in suspend should be idle. If that's the case you should clearly state this in the commit message and in code, although I don't know if it is safe to make such assumption. There could be user of the DMA that doesn't track the completion of transfers. > > Once the DMA in late_suspend is not be idle, we think some driver haven't canceled the DMA transmission. So maybe something is error when other driver in suspend. > > In the case, we should return failed to stop PM. DMA should not make a choice for other drivers(which used DMA) to force stop DMA transmission. The suspend entrance should be terminated by wakeup events and only critical issues. I don't think we should just terminate the suspend entrance just because having on-going I/O without even try to stop it. > > Thanks. > > Best Regards, > Yuan Yao > >> -----Original Message----- >> From: pku.leo@xxxxxxxxx [mailto:pku.leo@xxxxxxxxx] On Behalf Of Li Yang >> Sent: Friday, August 14, 2015 4:58 AM >> To: Yuan Yao-B46683 >> Cc: Vinod Koul; stefan@xxxxxxxx; Arnd Bergmann; Dan Williams; >> dmaengine@xxxxxxxxxxxxxxx; lkml; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux- >> pm@xxxxxxxxxxxxxxx >> Subject: Re: [PATCH v2] dmaengine: fsl-edma: add PM suspend/resume >> support >> >> On Tue, Jul 21, 2015 at 3:56 AM, Yuan Yao <yao.yuan@xxxxxxxxxxxxx> wrote: >> > This add power management suspend/resume support for the fsl-edma >> > driver. >> > >> > eDMA acted as a basic function used by others. What it needs to do is >> > the two steps below to support power management. >> > >> > In fsl_edma_suspend_late: >> > Check whether the DMA chan is idle and if it is not idle, stop PM >> > operation. >> >> You should try to quiesce the device on suspend instead of depending on itself >> to be happen in idle and failing if it is not. >> >> Regards, >> Leo -- - Leo -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
