From: Sascha Hauer <s.hauer@pengutronix.de>
To: "Robert P. J. Day" <rpjday@crashcourse.ca>
Cc: "U-Boot Version 2 (barebox)" <barebox@lists.infradead.org>
Subject: Re: what is the rationale for funny "0x100" offset for OMAP4 GPIO addresses?
Date: Wed, 5 Dec 2012 13:58:30 +0100 [thread overview]
Message-ID: <20121205125830.GH10369@pengutronix.de> (raw)
In-Reply-To: <alpine.DEB.2.02.1212050751380.5832@oneiric>
On Wed, Dec 05, 2012 at 07:54:51AM -0500, Robert P. J. Day wrote:
>
> i was going to submit a patch to replace magic constants for OMAP4
> with more meaningful names but i ran into an oddity. here's
> omap4-silicon.h:
>
> #define OMAP44XX_L4_WKUP_BASE 0x4A300000
> #define OMAP44XX_L4_PER_BASE 0x48000000
>
> and here's part of an old posting to the linux-omap mailing list:
>
> +/* GPIO controller*/
> +#define OMAP44XX_GPIO1_BASE (L4_WK_44XX_BASE + 0x10000)
> +#define OMAP44XX_GPIO2_BASE (L4_PER_44XX_BASE + 0x55000)
> +#define OMAP44XX_GPIO3_BASE (L4_PER_44XX_BASE + 0x57000)
> +#define OMAP44XX_GPIO4_BASE (L4_PER_44XX_BASE + 0x59000)
> +#define OMAP44XX_GPIO5_BASE (L4_PER_44XX_BASE + 0x5B000)
> +#define OMAP44XX_GPIO6_BASE (L4_PER_44XX_BASE + 0x5D000)
>
> but here's the tail end of omap4-generic.c:
>
> static int omap4_gpio_init(void)
> {
> add_generic_device("omap-gpio", 0, NULL, 0x4a310100,
> 0xf00, IORESOURCE_MEM, NULL);
> add_generic_device("omap-gpio", 1, NULL, 0x48055100,
> 0xf00, IORESOURCE_MEM, NULL);
> add_generic_device("omap-gpio", 2, NULL, 0x48057100,
> 0xf00, IORESOURCE_MEM, NULL);
> add_generic_device("omap-gpio", 3, NULL, 0x48059100,
> 0xf00, IORESOURCE_MEM, NULL);
> add_generic_device("omap-gpio", 4, NULL, 0x4805b100,
> 0xf00, IORESOURCE_MEM, NULL);
> add_generic_device("omap-gpio", 5, NULL, 0x4805d100,
> 0xf00, IORESOURCE_MEM, NULL);
>
> return 0;
> }
>
> as you can see, the numbers don't add up exactly -- the constants in
> that final file are all 0x100 larger than a simple addition. anyone
> know where that comes from?
This comes from the hardware. The GPIO controller is the same as on
omap3, but the base addresses have an additional 0x100 offset.
Sascha
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next prev parent reply other threads:[~2012-12-05 12:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-05 12:54 Robert P. J. Day
2012-12-05 12:58 ` Sascha Hauer [this message]
2012-12-05 13:01 ` Robert P. J. Day
2012-12-05 13:29 ` Robert P. J. Day
2012-12-05 14:11 ` Robert P. J. Day
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