On 15/10/20 9:24 am, Jisheng Zhang wrote: > On Thu, 15 Oct 2020 08:57:05 +0300 Adrian Hunter wrote: > >> >> >> On 15/10/20 5:38 am, Jisheng Zhang wrote: >>> On Thu, 15 Oct 2020 10:12:07 +0800 Jisheng Zhang wrote: >>> >>> >>>> >>>> On Wed, 14 Oct 2020 22:44:50 +0300 Adrian Hunter wrote: >>>> >>>>> >>>>> >>>>> + Chunyan >>>>> >>>>> On 14/10/20 1:32 pm, Jisheng Zhang wrote: >>>>>> Auto CMD Auto Select can only be used when v4_mode is enabled. >>>>> >>>>> The SDHCI spec. doesn't seem to say that. AFAICS it refers only to v4.1 not >>>>> v4 mode. >>>> >>>> 4.10 defines the "Auto CMD Auto Select" mode, v4 mode bit in SDHCI_HOST_CONTROL2 >>>> selects V3 compatible or V4 compatible mode, I think the v4 here includes >>>> v4.0, v4.1 and v4.2, so if we want to use the mode we have to ensure v4_mode >>> >>> So if we want to use the "Auto CMD Auto Select" mode, we have to ensure v4 mode >>> is enabled. >> >> But that is not exactly what the SDHCI spec. says. It is quite explicit >> about which registers and bit fields are affected by "Host Version 4 Enable =1". >> > > Just my humble opinion, this is implied, my logic look like: > > Host Version 4 Enable == 0 => only V3 compatible mode \ > => v4 mode is must for auto cmd auto select > No "Auto CMD Auto Select" definition in v3 spec / Ok, we will need the commit message to explain the performance degradation, and which driver / version / platform, and a comment in the code explaining we require Version 4 Mode for Auto CMD Auto Select because some controllers expect it that way.
