Re: [PATCH] mmc: sdhci: Use Auto CMD Auto Select only when v4_mode is true

[Jisheng Zhang <Jisheng.Zhang@synaptics.com>]

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      /

> So the question is whether this is standard or a quirk of your controller.
> 

other v4 controllers can do the same benchmark test after removing
sdhci_enable_v4_mode() in the controller's probe.


Thanks