linux-kernel - Re: [PATCH v3] mmc: renesas_sdhi: Fix change point of data handling

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Date: Mon, 5 Feb 2024 15:51:26 +0100
From: Wolfram Sang <wsa+renesas@...g-engineering.com>
To: claudiu beznea <claudiu.beznea@...on.dev>
Cc: ulf.hansson@...aro.org, yoshihiro.shimoda.uh@...esas.com,
	masaharu.hayakawa.ry@...esas.com, takeshi.saito.xv@...esas.com,
	linux-mmc@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH v3] mmc: renesas_sdhi: Fix change point of data handling


> > According to my understanding, we should only mark this TAP good if it
> > is in the range 5-7. I need to double check with Renesas, though.
> 
> OK, my understanding is that it should be in the middle (beginning being
> the tap that triggered change point of the input data, end being the next
> tap with the same ID). This is what I understand from this: "As the width
> of the input data is 1 (UI), select TAP6 or TAP7 which is
> 
> *the median* of next TAP3 from TAP3."

Yes, I agree. With 0x0e, that means TAP1+2+3 are changing points and we
should be far away from them, like 5-7.

But: I am still waiting for Renesas to answer my questions regarding
SMPCMP. I'd like to get that first, so we have clear facts then.

> > Boot failure is one test. Read/write tests should be another, I think.
> 
> OK, I'll try also read/write. Do you have in mind something particular?

Nope. Just consistency checks.

> > Because if we select a bad TAP, bad things might happen later. To reduce
> > the amount of testing, read/write testing could only be triggered if the
> > new code path was excecuted?
> 
> I'm not sure how to trigger that (or maybe I haven't understood your
> statement...)

I thought something in the lines of:

- print out when you needed SMPCMP to select a TAP
- check the log for that printout
- if (printout) do read_write_tests

Dunno if that makes sense with your test setup.


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