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Date: Mon, 5 Feb 2024 15:47:43 +0200
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Subject: Re: [PATCH v3] mmc: renesas_sdhi: Fix change point of data handling
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To: Wolfram Sang <wsa+renesas@sang-engineering.com>, ulf.hansson@linaro.org,
 yoshihiro.shimoda.uh@renesas.com, masaharu.hayakawa.ry@renesas.com,
 takeshi.saito.xv@renesas.com, linux-mmc@vger.kernel.org,
 linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org,
 Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
References: <20240205112702.213050-1-claudiu.beznea.uj@bp.renesas.com>
 <ZcDdn2AVz8FIXzak@shikoro>
From: claudiu beznea <claudiu.beznea@tuxon.dev>
In-Reply-To: <ZcDdn2AVz8FIXzak@shikoro>
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Hi, Wolfram,

On 05.02.2024 15:07, Wolfram Sang wrote:
> Hi Claudiu,
> 
> thanks for the updated version!
> 
>> To comply with this, the patch checks if this mismatch is present and
>> updates the priv->smpcmp mask only if it is not. Previous code checked if
>> the value of SMPCMP register was zero. However, on RZ/G3S, this leads to
>> failues as it may happen, e.g., the following:
>> CMPNGU=0x0e, CMPNGD=0x0e, SMPCMP=0x000e000e.
> 
> Can you add the current TAP number (variable 'i') to this printout?

This is a snapshot I have saved from my previous debugging session (but I
tried here to check the values of cmpngd, cmpngu):

i=0, cmpngu=00000000, cmpngd=00000000, smpcmp=00000000
i=1, cmpngu=00000000, cmpngd=00000000, smpcmp=00000000
i=2, cmpngu=0000000e, cmpngd=0000000e, smpcmp=000e000e
i=3, cmpngu=00000000, cmpngd=00000000, smpcmp=00000000
i=4, cmpngu=00000000, cmpngd=00000002, smpcmp=00000002
i=5, cmpngu=00000000, cmpngd=000000ff, smpcmp=000001ff
i=6, cmpngu=000000ff, cmpngd=00000000, smpcmp=01ff0000
i=7, cmpngu=00000000, cmpngd=00000000, smpcmp=00000000
i=8, cmpngu=00000000, cmpngd=00000000, smpcmp=00000000
i=9, cmpngu=00000000, cmpngd=00000000, smpcmp=00000000
i=10, cmpngu=00000000, cmpngd=00000000, smpcmp=00000000
i=11, cmpngu=00000000, cmpngd=00000000, smpcmp=00000000
i=12, cmpngu=00000000, cmpngd=00000002, smpcmp=00000002
i=13, cmpngu=00000000, cmpngd=000000ff, smpcmp=000001ff
i=14, cmpngu=000000ff, cmpngd=00000000, smpcmp=01ff0000
i=15, cmpngu=00000000, cmpngd=00000000, smpcmp=00000000

This is printed in this for loop:
https://elixir.bootlin.com/linux/latest/source/drivers/mmc/host/renesas_sdhi_core.c#L700

> 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."

> 
>> Along with it, as mmc_send_tuning() may return with error even before the
>> MMC command reach the controller (and because at that point cmd_error = 0),
>> the update of priv->smpcmp mask has been done only if the return value of
>> mmc_send_tuning(mmc, opcode, &cmd_error) is 0 (success).
> 
> This is a needed change, for sure.
> 
>> This change has been checked on the devices with the following DTSes by
>> doing 100 consecutive boots and checking for the tuning failure message:
> 
> 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?

> 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...)

Thank you,
Claudiu Beznea

> 
> Happy hacking,
> 
>    Wolfram
>