linux-kernel - Re: [PATCH 2.6.20-rc2] Add a quirk to allow at least some ENE PCI SD card readers to work again

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Message-ID: <4E9DE7C297%linux@youmustbejoking.demon.co.uk>
Date:	Sun, 31 Dec 2006 15:10:06 +0000
From:	Darren Salt <linux@...mustbejoking.demon.co.uk>
To:	linux-kernel@...r.kernel.org, drzeus-mmc@...eus.cx
Subject: Re: [PATCH 2.6.20-rc2] Add a quirk to allow at least some ENE PCI SD card readers to work again

I demand that Pierre Ossman may or may not have written...

> Darren Salt wrote:
>> Add a quirk to allow at least some ENE PCI SD card readers to work again

>> Support for these devices was broken for 2.6.18-rc1 and later by commit
>> 146ad66eac836c0b976c98f428d73e1f6a75270d, which added voltage level
>> support.

>> This restores the previous behaviour for these devices (PCI ID 1524:0550).

>> Signed-off-by: Darren Salt <linux@...mustbejoking.demon.co.uk>

> Oh? If this is the source of problems for ENE controllers then this is
> indeed a magnificent find. Good work.

> I'd like to know a little more about it though:

> - Exactly what errors where you seeing without this patch?

The device was recognised, but insertion of a card was effectively not being
noticed, with no messages in the kernel log. (I say 'effectively': interrupts
were definitely being received and processed.)

> - The patch effectively sets only the highest power. Have you tried other
> bit combinations to figure out if all of these are really needed?

I have now... bits 4 to 7 are ignored, so 0x0F is fine; and it's what's
needed since lower values don't work.

It turns out that the reader only supports one voltage (caps &
SDHCI_CAN_VDD_330 is true, the others are false) and the code was already
selecting the correct value for the hardware. So I tried reverting the patch
and ensuring that the first writeb() in sdhci_set_power() isn't done if the
second one will be - and things started working properly again.

> (This also means that the current patch is broken as the limited voltage
> range needs to also be reported to the MMC layer).

> - Could you change the patch so that it covers all ENE controllers and send
> it out for testing on sdhci-devel? That way we could see if there are any
> more ENE controllers that will benefit from this quirk. Just remember to
> ask people for a lspci.

Sent as a follow-up to this message.

(BTW, is there a version of Thunderbird which preserves Mail-Followup-To in
followups? I ask because I see that that header got lost...)

-- 
| Darren Salt    | linux or ds at              | nr. Ashington, | Toon
| RISC OS, Linux | youmustbejoking,demon,co,uk | Northumberland | Army
| + Generate power using sun, wind, water, nuclear.      FORGET COAL AND OIL.

File already exists, 0:1
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