> partitions > > On 6/10/19 7:59 AM, Peng Fan wrote: > >> Subject: Re: [U-Boot] [PATCH] mmc: Avoid HS400 mode when accessing > >> boot partitions > >> > >> Hi Marek, Peng, > >> > >> On 03/06/19 12:04 PM, Peng Fan wrote: > >>> > >>>> Subject: [PATCH] mmc: Avoid HS400 mode when accessing boot > >>>> partitions > >>>> > >>>> According to JEDEC JESD84-B51.pdf section 6.3.3 Boot operation , > >>>> HS200 & HS400 mode is not supported during boot operation. The > >>>> U-Boot code currently only applies this restriction to HS200 mode, > >>>> extend this to > >>>> HS400 mode as well. > >> The spec in section 6.3.3 (according to my understanding) is talking > >> about "boot operation" which is a way of getting data from the the > >> eMMC without going through the Device identification mode (Section > >> 6.4.4) i.e. without sending any commands. All the host has to do is > >> hold the command line low in Pre-Idle mode to automatically receive > >> data at the preconfigured frequency and bus width. > >> > >> When U-boot is accessing the partition, it has already gone through > >> the Device identification mode and is in data transfer mode (i.e. it > >> needs to send commands for read/write to happen). In this case, we > >> need to switch the partition in Extended CSD to access the boot > >> partition (Section 6.2.5). The spec doesn't say anything about HS200 and > HS400 not being supported here. > > > > Yes, the spec does not mention this. It only mentions HS200/400 not > > supported during boot operation. > > > >> > >> Also, I don't see linux kernel switching down speed when trying to > >> access a boot partition (unless its being very sneaky about it). So > >> if you are seeing issues with accessing boot partitions at > >> HS200/HS400 then you should probably look at how linux code is working > instead. > > > > There might be bug in U-Boot code. > > So are we gonna leave this inconsistency in for current release or what's it > gonna be ? Like I said, we're in rc3, it's fine to do bigger changes in next > release, but we should at least fix this in current release.
I'll pick up your patch in this release. Regards, Peng. > > I would also like to hear from Jean why he originally introduced this for > HS200 > mode. > > -- > Best regards, > Marek Vasut _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
