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 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
