[U-Boot] [PATCH 4/6] mmc: Continue polling MMC card for OCR only if it is still not ready

[Andrew Gabbasov]

> From: Troy Kisky [mailto:troy.kisky at boundarydevices.com]
> Sent: Tuesday, March 24, 2015 9:03 PM
> To: Gabbasov, Andrew; Peng.Fan at freescale.com; u-boot at lists.denx.de
> Cc: Eric Nelson
> Subject: Re: [U-Boot] [PATCH 4/6] mmc: Continue polling MMC card for OCR
> only if it is still not ready
> 
> On 3/24/2015 9:33 AM, Andrew Gabbasov wrote:
> > Hi Troy,
> >
> >> From: Troy Kisky [mailto:troy.kisky at boundarydevices.com]
> >> Sent: Monday, March 23, 2015 11:09 PM
> >> To: Gabbasov, Andrew; Peng.Fan at freescale.com; u-boot at lists.denx.de
> >> Cc: Eric Nelson
> >> Subject: Re: [U-Boot] [PATCH 4/6] mmc: Continue polling MMC card for
> >> OCR only if it is still not ready
> >>
> >> On 3/23/2015 12:38 AM, Andrew Gabbasov wrote:
> >>> Hi Troy,
> >>>
> >>>> From: Troy Kisky [mailto:troy.kisky at boundarydevices.com]
> >>>> Sent: Friday, March 20, 2015 9:39 PM
> >>>> To: Peng.Fan at freescale.com; Gabbasov, Andrew; u-boot at lists.denx.de
> >>>> Cc: Eric Nelson
> >>>> Subject: Re: [U-Boot] [PATCH 4/6] mmc: Continue polling MMC card
> >>>> for OCR only if it is still not ready
> >>>>
> >>>> [skipped]
> >>>>
> >>>> Here's another patch that solves the problem a little earlier. It
> >>>> has this disadvantage of being slightly bigger, though it makes the
> >>>> code look
> >>> better.
> >>>>
> >>>> https://github.com/boundarydevices/u-boot-imx6/commit/c0260ca
> >>>>
> >>>
> >>> I have a couple of doubts regarding that patch.
> >>>
> >>> First, my personal taste objects to such duplicating of the code (I
> >>> mean setting of version, ocr, rca, etc fields of mmc structure).
> >>> If we'll have to change or add anything to these settings, we'll
> >>> have to make the same change in 2 different place, which is
> >>> error-prone and extremely inconvenient from maintenance point of view.
> >>>
> >>> Second, what about SPI mode? Doesn't this patch skip retrieving of
> >>> OCR register with a special command for SPI host case (thus setting
> >>> ocr field incorrectly), if the card comes to ready state with the
> >>> first attempt?
> >>
> >> That's a good argument for a subroutine to be doing that work instead
> >> of
> > in two
> >> places.
> >
> > In some sense the second function of these two
> > (mmc_complete_op_cond()) is exactly such subroutine ;-) It is doing
> > this work of final settings and actions after making OCR polling.
> > Although completing the polling itself in some cases too.
> > Actually, it seems that introducing of one more service function would
> > make the code a little too "chopped" into too small pieces, and also
> > further less similar to SD (as opposed to MMC) case.
> >
> > Thanks.
> >
> 
> I've already said that I'm fine with any patch that fixes the problem, so
there is
> no need to convince me of anything. I just wanted to show that setting the
> pending flag, when the command is actually complete, does not make a lot
of
> sense.

I absolutely agree. In fact, this flag in current implementation just
indicates
the branch that the MMC card case is being processed. If the version field,
differing SD and MMC cases, would be set a little earlier, for example,
directly in mmc_start_init(), we could just use !IS_SD() instead of this
pending flag. And thinking further, it's not quite clear why the splitting
of OCR polling was done for MMC case only, but not for SD too.
So, there is still the room for further improving the code, may be even
some reorganizing, but I had to stop somewhere, unless there is
the direct necessity ;-)

Thanks.

Best regards,
Andrew