From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Carlos Aguiar <carlos.aguiar@indt.org.br>
Cc: linux-kernel@vger.kernel.org, Tony Lindgren <tony@atomide.com>,
Pierre Ossman <drzeus-list@drzeus.cx>
Subject: Re: [RFC] mmc: add OMAP driver
Date: Thu, 16 Feb 2006 16:59:58 +0000 [thread overview]
Message-ID: <20060216165957.GC29443@flint.arm.linux.org.uk> (raw)
In-Reply-To: <43F48BCA.8010608@indt.org.br>
One additional comment on the patch which I missed, and has shown to
be a related cause of problems on a different host controller...
On Thu, Feb 16, 2006 at 10:27:22AM -0400, Carlos Aguiar wrote:
> +static inline void set_data_timeout(struct mmc_omap_host *host, struct mmc_request *req)
> +{
> + int timeout;
> + u16 reg;
> +
> + /* Convert ns to clock cycles by assuming 20MHz frequency
> + * 1 cycle at 20MHz = 500 ns
> + */
> + timeout = req->data->timeout_clks + req->data->timeout_ns / 500;
> +
> + /* Some cards require more time to do at least the first read operation */
> + timeout = timeout << 4;
This is a hack because you got your calculation above wrong. If you
assume a fast clock, the timeout will be too slow for a slower clock.
If you do the calculation correctly and you won't need such hacks.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
next prev parent reply other threads:[~2006-02-16 17:00 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-16 14:27 [RFC] mmc: add OMAP driver Carlos Aguiar
2006-02-16 15:15 ` Russell King
2006-02-16 16:59 ` Russell King [this message]
2006-02-24 16:38 ` Carlos Aguiar
2006-02-24 20:48 ` Russell King
[not found] ` <5b5833aa0603030926h5d2c357eoe203a40248796013@mail.gmail.com>
[not found] ` <48b7761d0603030942l53fcd2bbl249297461a54dd3c@mail.gmail.com>
2006-03-03 17:49 ` Carlos Eduardo
2006-03-07 20:53 ` Carlos Aguiar
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