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From: "Robert P. J. Day" <rpjday@crashcourse.ca>
To: "U-Boot Version 2 (barebox)" <barebox@lists.infradead.org>
Subject: what is the rationale for funny "0x100" offset for OMAP4 GPIO addresses?
Date: Wed, 5 Dec 2012 07:54:51 -0500 (EST)	[thread overview]
Message-ID: <alpine.DEB.2.02.1212050751380.5832@oneiric> (raw)


  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?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

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             reply	other threads:[~2012-12-05 12:54 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-12-05 12:54 Robert P. J. Day [this message]
2012-12-05 12:58 ` Sascha Hauer
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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