From: claudiu beznea <claudiu.beznea@tuxon.dev>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>,
ulf.hansson@linaro.org, takeshi.saito.xv@renesas.com,
masaharu.hayakawa.ry@renesas.com,
yoshihiro.shimoda.uh@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>
Subject: Re: [PATCH v2] mmc: renesas_sdhi: Fix change point of data handling
Date: Tue, 30 Jan 2024 09:51:41 +0200 [thread overview]
Message-ID: <7c4f6031-ac7b-407c-a223-e7b65ef8baa7@tuxon.dev> (raw)
In-Reply-To: <ZbikovLbujyGS1ub@ninjato>
On 30.01.2024 09:26, Wolfram Sang wrote:
> Hi Claudiu,
>
>> My understanding was the other way around from this statement found in
>> RZ/G3S hw manual:
>>
>> "If all of the TAP [i] is OK, the sampling clock position is selected by
>> identifying the change point of data.
>
> Yes, it is easy to misunderstand. It should add "and avoid it" or
> something. I got an internal diagram which makes it more clear. I just
> asked if I can share it with you.
>
>>> I also have a chapter named like this. If you check the diagram, change
>>> point is between TAP2 and 3, so the suggested TAP to use is 6 or 7. As
>>> far away as possible from the change point.
>>
>> My understanding was different here as of the following hw manual statement:
>>
>> "As the width of the input data is 1 (UI), select TAP6 or TAP7 which is
>>
>> *the median* of next TAP3 from TAP3"
>>
>> I understand from this that the median value should be considered here.
>
> Sorry, can't follow you here. "Select TAP6 or TAP7" is clear to me. But
> it doesn't really matter why it was misleading...
>
>>> However, with some SD cards, I also see the EIO error you see. So, there
>>> might be room to improve TAP selection when all TAPs are good. I need to
>>> check if this is really is the same case for the SD cards in question.
>>
>> Maybe better would be to change this condition:
>>
>> if (cmpngu_data != cmpngd_data)
>> set_bit(i, priv->smpcmp);
>>
>> like this:
>> if (cmpngu_data == cmpngd_data)
>> set_bit(i, priv->smpcmp);
>>
>> ?
>>
>> I need to check it, though.
>
> But isn't it equal to the current code then? (Except for one thing: the
From my debugging session I remember the SMPCMP was not zero and this lead
to my failure.
I'm not sure (and I don't remember from my debugging session) if CMPNGU and
CMPNGD are identical after the change point of the input data (CMPNGU !=
CMPNGD) has been signaled by the controller. I need to check it.
> smpcmp bit is only set when there is no cmd error. I need to double
> check but I think I like that.)
>
> Happy hacking,
>
> Wolfram
>
prev parent reply other threads:[~2024-01-30 7:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-17 11:06 [PATCH v2] mmc: renesas_sdhi: Fix change point of data handling Claudiu
2024-01-17 14:06 ` Wolfram Sang
2024-01-29 10:43 ` Wolfram Sang
2024-01-29 10:55 ` Wolfram Sang
2024-01-30 7:03 ` claudiu beznea
2024-01-30 7:26 ` Wolfram Sang
2024-01-30 7:31 ` Wolfram Sang
2024-01-30 7:51 ` claudiu beznea [this message]
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