Re: [PATCH] MMC Agressive clocking framework v6

From: Linus Walleij <linus.ml.walleij@gmail.com>
To: David Vrabel <david.vrabel@csr.com>
Cc: linux-mmc@vger.kernel.org, Ghorai Sukumar <s-ghorai@ti.com>,
	Chris Ball <cjb@laptop.org>, Nicolas Pitre <nico@fluxnic.net>,
	Adrian Hunter <adrian.hunter@nokia.com>
Subject: Re: [PATCH] MMC Agressive clocking framework v6
Date: Mon, 1 Nov 2010 16:24:40 +0100	[thread overview]
Message-ID: <AANLkTiki-PGJHMcrRCwA46W+-xmj+AdpxLMFdd2mfdhM@mail.gmail.com> (raw)
In-Reply-To: <4CCEA435.9030402@csr.com>

2010/11/1 David Vrabel <david.vrabel@csr.com>:
> On 29/10/2010 21:18, Linus Walleij wrote:
>> This patch modifies the MMC core code to optionally call the
>> set_ios() operation on the driver with the clock frequency set
>> to 0 (gate) after a grace period of at least 8 MCLK cycles, then
>> restore it (ungate) before any new request. This gives
>> the driver the option to shut down the MCI clock to the MMC/SD
>> card when the clock frequency is 0, i.e. the core has stated
>> that the MCI clock does not need to be generated.
>
> With SDIO cards, 1 bit mode needs to be set on the controller otherwise
> many controllers cannot detect card interrupts.

Do you mean generally, or just when disabling the clock?
I don't quite get this part...

> Also some v2.00 SDIO cards in 4-bit mode will not generate card
> interrupts unless they are clocked (the spec v2.00 doesn't require them
> to be able to but v3.00 does).

OK I think it is better to disable clocking off SDIO cards altogether
for now.

> I would suggest a white list of v2.00
> cards that can generate interrupts asynchronousy.

Hm... does people maintain such lists? Sounds tricksy.
Better avoid it for the time being.

Linus Walleij