Hi Marek, On 04/06/19 6:56 PM, Marek Vasut wrote: > On 6/4/19 1:22 PM, Faiz Abbas wrote: >> Hi Marek, Peng, > > Hi, > >> 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. >> >> 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. > > Did you practically verify this ? In my case, the boot partition access > fails in HS200/HS400 mode (samsung and sandisk emmc, but I'd have to > check the exact part number). > > commit 01298da31d92ecc46cf9130d8cff68bc51698197 > mmc: Change mode when switching to a boot partition > seems to confirm that too. >
I had tried to raise these concerns for that patch as well (https://www.spinics.net/lists/linux-mmc/msg50432.html) but it was missed at that time. I did verify that kernel is not switching speeds on a dra7xx board. JJ and I have seen failures similar to yours in u-boot (which led to this patch) but not in kernel which makes me think that the fix was wrong. Have you verified with your setup in kernel? Thanks, Faiz _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
