Re: [RFT] arm64: dts: renesas: salvator-common: enable SDR104 for SD cards

From: Wolfram Sang <wsa@the-dreams.de>
To: Simon Horman <horms@verge.net.au>
Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>,
	linux-renesas-soc@vger.kernel.org, linux-mmc@vger.kernel.org
Subject: Re: [RFT] arm64: dts: renesas: salvator-common: enable SDR104 for SD cards
Date: Tue, 8 Aug 2017 20:54:45 +0200	[thread overview]
Message-ID: <20170808185445.GA2170@katana> (raw)
In-Reply-To: <20170803155520.GB3826@verge.net.au>

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> As it is an "RFT" I'm happy to apply it if you repost
> it or otherwise indicate that is what you would like to happen.

As discussed in a chat, I tried SDR104 with my SDIO WiFi cards:

H3:
- one slot worked flawlessly
- one slot could load FW but failed to read status
(with SDR50: both slots work)

M3-W:
- both slots could not load the firmware
(with SDR50: one slot works, one fails to load FW)

The cards, however, were correctly identified as SDR104 and there were
no tuning errors and no other SDHI related warnings.

Changing TDSEL in the PFC did not change anything.

The manual of the WiFi card (u-blox EMMY-W1) mentions a maximum line
length of 100mm. Measuring a direct line from the SoC to the slots,
I'd think we are very much on the edge of that. And given the length
of the SDIO adapter, we are surely exceeding that :(

Maybe we should do more tests with more boards? On the other hand, it
seems the WiFi card is running out of the specs.

So much for now. I'll sleep over it and try to get more data tomorrow.

Regards,

   Wolfram

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