mmc: add bcm2835 driver

This adds a simple driver for the BCM2835's SD controller.

Workarounds are implemented for:
* Register writes can't be too close to each-other in time, or they will
  be lost.
* Register accesses must all be 32-bit, so implement custom accessors.

This code was extracted from:
git://github.com/gonzoua/u-boot-pi.git master
which was created by Oleksandr Tymoshenko.

Portions of the code there were obviously based on the Linux kernel at:
git://github.com/raspberrypi/linux.git rpi-3.6.y
commit f5b930b "Main bcm2708 linux port" signed-off-by Dom Cobley.

swarren changed the following for upstream:
* Removed hack udelay()s in bcm2835_sdhci_raw_writel(); setting
  SDHCI_QUIRK_WAIT_SEND_CMD appears to solve the issues.
* Remove register logging from read*/write* functions.
* Sort out confusion with min/max_freq values passed to add_sdhci().
* Use more descriptive variable names and calculations in IO accessors.
* Simplified and commented twoticks_delay calculation.
* checkpatch fixes.

Cc: Andy Fleming <afleming@gmail.com>
Signed-off-by: Oleksandr Tymoshenko <gonzo@bluezbox.com>
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Andy Fleming <afleming@gmail.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/arch/arm/include/asm/arch-bcm2835/sdhci.h b/arch/arm/include/asm/arch-bcm2835/sdhci.h
new file mode 100644
index 0000000..a4f867b
--- /dev/null
+++ b/arch/arm/include/asm/arch-bcm2835/sdhci.h
@@ -0,0 +1,24 @@
+/*
+ * (C) Copyright 2012 Stephen Warren
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _BCM2835_SDHCI_H_
+#define _BCM2835_SDHCI_H_
+
+#define BCM2835_SDHCI_BASE 0x20300000
+
+int bcm2835_sdhci_init(u32 regbase, u32 emmc_freq);
+
+#endif