linux-kernel - Re: [PATCH v4] mmc: Make ID freq configurable

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Date:	Fri, 03 Dec 2010 05:21:10 +0800
From:	Hein_Tibosch <hein_tibosch@...oo.es>
To:	Sahitya Tummala <stummala@...eaurora.org>,
	Michal Miroslaw <mirq-linux@...e.qmqm.pl>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Pierre Ossman <pierre@...man.eu>, Chris Ball <cjb@...top.org>,
	Ben Nizette <bn@...sdigital.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Adrian Hunter <adrian.hunter@...ia.com>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Matt Fleming <matt@...sole-pimps.org>
Subject: Re: [PATCH v4] mmc: Make ID freq configurable

Hi Sahitya,

On 2-12-2010 19:16, Sahitya Tummala wrote:
> Hi Hein Tibosch,
>
> On Fri, 2010-09-03 at 05:34 +0800, Hein_Tibosch wrote:
>> In the latest releases of the mmc driver, the freq during initialization
>> is set to a fixed 400 Khz. This was reportedly too fast for several
>> users. As there doesn't seem to be an ideal frequency which-works-for-all,
>> Pierre suggested to let the driver try several frequencies.
>> <cut>
>> +		/*
>> +		 * First we search for SDIO...
>> +		 */
>> +		err = mmc_send_io_op_cond(host, 0, &ocr);
>> +		if (!err) {
>> +			if (mmc_attach_sdio(host, ocr)) {
>> +				mmc_claim_host(host);
>> +				/* try SDMEM (but not MMC) even if SDIO is broken */
>> +				if (mmc_send_app_op_cond(host, 0, &ocr))
> In case of SDIO error, mmc_power_off() is getting called as part of
> mmc_detach_bus().  Shouldn't we power up the host before checking for
> SDMEM? Any comments?
>
I think you should ask Michal Miroslaw, as he wrote the patch for the
SD-combo (IO + mem)*

But yes, in case of a failure, mmc_attach_sdio() will call mmc_detach_bus()
which in turn will call mmc_power_off()

And so it should be mmc_power_up() again before trying to detect SD memory.


Hein Tibosch

* http://permalink.gmane.org/gmane.linux.kernel.mmc/2052
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