On 6/11/19 3:17 AM, Peng Fan wrote: >> 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.
Right. But I would still like to know whether we can access the HW partitions in HS modes or not. And I would also like to know why we originally prevented it. -- Best regards, Marek Vasut _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
