Re: [PATCH] Revert "spi: modify set_cs_timing parameter"

[Dafna Hirschfeld]

On 30.09.21 14:46, Mark Brown wrote:
> On Thu, Sep 30, 2021 at 02:36:01PM +0200, Dafna Hirschfeld wrote:
> > hi, thanks for the fast feedback
> >
> > On 30.09.21 14:25, Mark Brown wrote:
> > > On Thu, Sep 30, 2021 at 02:07:00PM +0200, Dafna Hirschfeld wrote:
> > > > This reverts commit 04e6bb0d6bb127bac929fb35edd2dd01613c9520.
>
> > > Which is not what the commit message nor the paste of the full hash
> > > claimed :/
>
> > What is the paste of the full hash?
>
> The above.
>
> > Since the second commit is only a warning fixes I thought it is cumbersome to
> > send two separate reverting patches. Should I?
>
> No, you should write a proper commit log with (like I said) a normal
> subject line - basically, follow the process in submitting-patches.rst.
>
> > > Do we have any analysis as to why?  Do these devices use timing
> > > parameters in some way for example, or do the values written out to the
> > > device change in some way?
>
> > > You've provided no analysis here so it's hard to tell if this is just
> > > some random change that happens to change code generation slighly or if
> > > there's some actual reason why this might fix something.  I'll note that
> > > as far as I can see there are no users of this API upstream so I'm
> > > guessing that you've got some out of tree consumer driver which uses the
> > > API, it's possible that there was some error in updating that driver to
> > > the new interface which is causing the issue.
>
> > Actually the original commit not only change that callback 'set_cs_timing' but it also
> > calls 'mtk_spi_set_hw_cs_timing' directly from the function "mtk_spi_prepare_message".
> > So this actually influences all devices bound to this driver (in upstream)
> > I did some printing and it does change values that are written to registers.
>
> OK, so that's something that should have been in the commit log,
> preferrably in a more detailed form that identifies what the change is.
> However changing the values written out is clearly not the intent of the
> patch and it is a substantially better API so can we not just fix things
> so that the old values are written out?  Why are we jumping straight to
> a revert here?

It could be that the values written to the register in the new version of "mtk_spi_set_hw_cs_timing" are the same
as with the previous version. I didn't check that. The difference is that before that patch
the function was not called so it was a dead code. Now it is called and causes erros.
Without the datasheet it is hard to know how to fix it. I responded to that patch two days ago explaining
that but Mason Zhang didn't respond yet.

Thanks,
Dafna

>