From: Sascha Hauer <s.hauer@pengutronix.de>
To: Juergen Beisert <jbe@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: [RFC] MXS/i.MX23: detecting the boot source
Date: Tue, 21 May 2013 08:57:18 +0200 [thread overview]
Message-ID: <20130521065718.GK32299@pengutronix.de> (raw)
In-Reply-To: <201305171018.39539.jbe@pengutronix.de>
On Fri, May 17, 2013 at 10:18:39AM +0200, Juergen Beisert wrote:
> The boot source for the i.MX23 is configured via a few GPIOs, which are later
> be used for different purposes (like LCD data for example). The SoC internal
> ROM reads these GPIOs and uses the selected boot source.
>
> For various reasons the boot source is also of interest when Barebox is running.
> This detection approach reads again the GPIOs. It switches temporarily the pins
> to act as GPIOs and input, reads their values, and switches back to their
> previous functions.
>
> Could this be a reliable way to detect the boot source?
I don't know. Are the bootstrap pins used as outputs only in the normal
usecase? Otherwise I could imagine that something is overriding the
bootstrap pins by the time you read them.
>
> BTW: is there a reason why the bootsource will create environment variables,
> while other detected features find their way to the "global" device?
No, at least not a good one ;)
> +static uint32_t mxs23_boot_save_loc(void)
Should you continue working on this please change the name to something
like mx23_get_bootsource(). This function does not save anything.
Sascha
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next prev parent reply other threads:[~2013-05-21 6:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-17 8:18 Juergen Beisert
2013-05-21 6:57 ` Sascha Hauer [this message]
2013-05-21 8:01 ` Juergen Beisert
2013-05-21 8:44 ` [PATCH] MXS/i.MX23: add boot source detection Juergen Beisert
2013-05-23 7:54 ` Sascha Hauer
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