On 04/04/13 17:58, Ulf Hansson wrote: > On 4 April 2013 14:00, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >> On 04/04/13 14:52, Ulf Hansson wrote: >>> On 4 April 2013 13:44, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >>>> On 04/04/13 12:55, Ulf Hansson wrote: >>>>> On 4 April 2013 10:46, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >>>>>> On 01/03/13 14:47, Ulf Hansson wrote: >>>>>>> From: Ulf Hansson <ulf.hansson@xxxxxxxxxx> >>>>>>> >>>>>>> The mmc_power_restore|save_host API is only used by SDIO func drivers. SDIO >>>>>> >>>>>> NAK - it is also used by eMMC hardware reset i.e. mmc_do_hw_reset() >>>>> >>>>> True for eMMC, but for SD card the bus_ops can go away. Thanks for >>>>> spotting this Adrian! >>>>> >>>>> Although, I see some serious problems with the mmc_do_hw_reset >>>>> function - it could cause eMMC data corruption. >>>>> >>>>> Issuing hw reset and doing re-initialization by using the mmc >>>>> bus_ops->power_restore will mean no consideration is taken to "cache >>>>> ctrl", "bkops" and "power off notify". I think it must. >>>>> >>>>> So the more proper way instead of calling power_restore, should be to >>>>> use bus_ops->suspend and bus_ops->resume callbacks from the >>>>> mmc_do_hw_reset function. Additionally if bus_ops->suspend is done >>>>> successfully, we should be able to skip the actual hw reset and just >>>>> do bus_ops->resume. >>>>> >>>>> Do you have any thoughts on this? >>>> >>>> Certainly the bootloader should leave the eMMC is a safe state including: >>>> flushing the cache or turning it off (why did it turn on?), stopping >>>> background operations (why did it start them?), disabling power-off >>>> notification CMD0? (again why it it enable it?) >>> >>> Not sure what you mean here. What has a booloader to do with this? >> >> When do you think hw reset is used? > > Two types is being used. > > 1. At the mmc_rescan sequence. At this point mmc_do_hw_reset is _not_ > used. Instead mmc_hw_reset_for_init, which onlcy makes use of > host->ops->hw_reset, no "power_restore" of course. So this has no > issues whatsoever with this patch. > > 2. At blk request errors, which I thought we were discussing from the > beginning. In this case mmc_do_hw_reset is used. And it here my > proposals doing bus_ops->suspend|resume make sense. > > >> >>> >>>> >>>> Note that according to spec. CMD0 anyway clears the cache so you have lost >>>> your data anyway. >>> >>> What I am saying that we can try send "cache ctrl" and "power off >>> notify" before we send CMD0 / do hw reset. The no data shall be lost. >> >> With an uninitialized bus? Or an unresponsive card? > > See above. > > The bus is never uninitialized. > > The card has responded with an error, but that does not have to mean > that it is completely "unresponsive". True. Arguably caching should be disabled at the first sign of trouble and never re-enabled. However reset could attempt to flush the cache. Then, even if the reset is successful, an error must still be returned if the flush failed. -- 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
