linux-kernel - Re: [RFC] sdhci: use ios->clock to know when sdhci is idle

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Date:	Sun, 2 Jan 2011 22:08:10 +0100
From:	Pierre Tardy <tardyp@...il.com>
To:	Linus Walleij <linus.ml.walleij@...il.com>
Cc:	"Gao, Yunpeng" <yunpeng.gao@...el.com>,
	"Yuan, Hang" <hang.yuan@...el.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Chris Ball <cjb@...top.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...ux.intel.com>, Takashi Iwai <tiwai@...e.de>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	Ohad Ben-Cohen <ohad@...ery.com>
Subject: Re: [RFC] sdhci: use ios->clock to know when sdhci is idle

> Not all SDIO cards will work properly if you try to gate them
> so we need a mechanism to selectively do this.
You are right..##??!! HW vendors that does not support standards...

AFAIK (was working on a sdio HW IP team before), the sdio clock is not
supposed to be taken as is for a system clock derivative especially
because it can stop between request.
SDIO IRQ are asynchronous when a command or data is not ongoing

> Any suggestions?
I would personally suggest white list from drivers. With a call to
mmc_host_allow_gate_card(struct mmc_card *card, bool allow)

see following patch..

Regards,
-- 
Pierre
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