linux-kernel - Re: [PATCH 0/6] mmc: core: hs400(es) fix probe/init

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Message-ID: <CAPDyKFpu-qGPK1XZJ34itTm+12s9zwqfyReX0gd26MkH6vkSYw@mail.gmail.com>
Date:   Fri, 22 Jan 2021 13:40:20 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Chris Ruehl <chris.ruehl@...ys.com.hk>,
        Adrian Hunter <adrian.hunter@...el.com>
Cc:     "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Ludovic Barre <ludovic.barre@...com>,
        Krishna Konda <kkonda@...eaurora.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jack <jack.lo@...ys.com.hk>
Subject: Re: [PATCH 0/6] mmc: core: hs400(es) fix probe/init

+ Adrian

On Tue, 8 Dec 2020 at 07:19, Chris Ruehl <chris.ruehl@...ys.com.hk> wrote:
>
> Fix the probe if hs400-1_8v / hs400-1_2v is used in the
> dts and mmc-hs400-enhanced-strobe isn't set.
> That was the first attemped, but it turns out that some
> more cleanups and simplifications can be done.

My apologies for the delay with reviewing. I have looped in Adrian as
well, as he might have some input to our discussion.

Before I go into doing a detailed review, I want to make sure I
understand the problem correctly.

Are you saying that switching to eMMC HS400 mode doesn't work, unless
the enhanced strobe is supported, no? Or is this a DT only related
problem?

In any case, the main point with mmc_hs400_to_hs200() is to prepare
for tuning to run in HS200 mode (it's getting called from
mmc_retune()). In other words, there *should* be no need to support
enhanced strobe to support hs400, but I might be missing something.

In particular, the following commit could be of interest for you:

6376f69d20a6905c1d83be451065f70200490b98
Author: Adrian Hunter <adrian.hunter@...el.com>
Date:   Thu May 7 13:10:20 2015 +0300
mmc: core: Add support for HS400 re-tuning

>
> * move mmc_select_hs400() in between hs200 & hs400es (preparation)
> * make mmc_select_hs400() independent and move it out
>   of the hs200. Run hs400 tuning inside mmc_select_hs400();
> * merge hs400 with hs400es function
> * remove mmc_select_hs400es function
> * remove mmc_hs200_tuning()
> * cleanup host->caps2 for hs400-1_8(2)v
>
>
> Signed-off-by: Chris Ruehl <chris.ruehl@...ys.com.hk>
> ---
> Replace patch set [PATCH 0/3] mmc: core: hs400 fix probe

Kind regards
Uffe