linux-kernel - Re: [PATCH v6 03/12] mmc: mmci: Add enough delay between writes to CMD register.

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Date:	Wed, 11 Jun 2014 14:46:10 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:	Russell King <linux@....linux.org.uk>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Chris Ball <chris@...ntf.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v6 03/12] mmc: mmci: Add enough delay between writes to
 CMD register.

On Mon, Jun 2, 2014 at 11:08 AM,  <srinivas.kandagatla@...aro.org> wrote:

> From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>
> On Qcom SD Card controller POWER, CLKCTRL, DATACTRL and COMMAND registers
> should be updated in MCLK domain, and writes to these registers must be
> separated by three MCLK cycles. This resitriction is not applicable for
> other registers. Any subsequent writes to these register will be ignored
> until 3 MCLK have passed.
>
> One usec delay between two CMD register writes is not sufficient in the
> card identification phase where the CCLK is very low. This patch replaces
> a static 1 usec delay to use mmci_reg_delay function which can provide
> correct delay depending on the cclk frequency.
>
> Without this patch the card is not detected.
>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>

Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij
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