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>

2 files changed, 190 insertions, 0 deletions

diff --git a/drivers/mmc/Makefile b/drivers/mmc/Makefile
index 65791aa..1d6faa2 100644
--- a/drivers/mmc/Makefile
+++ b/drivers/mmc/Makefile
@@ -43,6 +43,7 @@ COBJS-$(CONFIG_MXS_MMC) += mxsmmc.o
 COBJS-$(CONFIG_OMAP_HSMMC) += omap_hsmmc.o
 COBJS-$(CONFIG_PXA_MMC_GENERIC) += pxa_mmc_gen.o
 COBJS-$(CONFIG_SDHCI) += sdhci.o
+COBJS-$(CONFIG_BCM2835_SDHCI) += bcm2835_sdhci.o
 COBJS-$(CONFIG_S5P_SDHCI) += s5p_sdhci.o
 COBJS-$(CONFIG_SH_MMCIF) += sh_mmcif.o
 COBJS-$(CONFIG_TEGRA_MMC) += tegra_mmc.o
diff --git a/drivers/mmc/bcm2835_sdhci.c b/drivers/mmc/bcm2835_sdhci.c
new file mode 100644
index 0000000..b0afc3c
--- /dev/null
+++ b/drivers/mmc/bcm2835_sdhci.c
@@ -0,0 +1,189 @@
+/*
+ * This code was extracted from:
+ * git://github.com/gonzoua/u-boot-pi.git master
+ * and hence presumably (C) 2012 Oleksandr Tymoshenko
+ *
+ * Tweaks for U-Boot upstreaming
+ * (C) 2012 Stephen Warren
+ *
+ * Portions (e.g. read/write macros, concepts for back-to-back register write
+ * timing workarounds) obviously extracted from the Linux kernel at:
+ * https://github.com/raspberrypi/linux.git rpi-3.6.y
+ *
+ * The Linux kernel code has the following (c) and license, which is hence
+ * propagated to Oleksandr's tree and here:
+ *
+ * Support for SDHCI device on 2835
+ * Based on sdhci-bcm2708.c (c) 2010 Broadcom
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/* Supports:
+ * SDHCI platform device - Arasan SD controller in BCM2708
+ *
+ * Inspired by sdhci-pci.c, by Pierre Ossman
+ */
+
+#include <common.h>
+#include <malloc.h>
+#include <sdhci.h>
+
+/* 400KHz is max freq for card ID etc. Use that as min */
+#define MIN_FREQ 400000
+
+struct bcm2835_sdhci_host {
+	struct sdhci_host host;
+	uint twoticks_delay;
+	ulong last_write;
+};
+
+static inline struct bcm2835_sdhci_host *to_bcm(struct sdhci_host *host)
+{
+	return (struct bcm2835_sdhci_host *)host;
+}
+
+static inline void bcm2835_sdhci_raw_writel(struct sdhci_host *host, u32 val,
+						int reg)
+{
+	struct bcm2835_sdhci_host *bcm_host = to_bcm(host);
+
+	/*
+	 * The Arasan has a bugette whereby it may lose the content of
+	 * successive writes to registers that are within two SD-card clock
+	 * cycles of each other (a clock domain crossing problem).
+	 * It seems, however, that the data register does not have this problem.
+	 * (Which is just as well - otherwise we'd have to nobble the DMA engine
+	 * too)
+	 */
+	while (get_timer(bcm_host->last_write) < bcm_host->twoticks_delay)
+		;
+
+	writel(val, host->ioaddr + reg);
+	bcm_host->last_write = get_timer(0);
+}
+
+static inline u32 bcm2835_sdhci_raw_readl(struct sdhci_host *host, int reg)
+{
+	return readl(host->ioaddr + reg);
+}
+
+static void bcm2835_sdhci_writel(struct sdhci_host *host, u32 val, int reg)
+{
+	bcm2835_sdhci_raw_writel(host, val, reg);
+}
+
+static void bcm2835_sdhci_writew(struct sdhci_host *host, u16 val, int reg)
+{
+	static u32 shadow;
+	u32 oldval = (reg == SDHCI_COMMAND) ? shadow :
+		bcm2835_sdhci_raw_readl(host, reg & ~3);
+	u32 word_num = (reg >> 1) & 1;
+	u32 word_shift = word_num * 16;
+	u32 mask = 0xffff << word_shift;
+	u32 newval = (oldval & ~mask) | (val << word_shift);
+
+	if (reg == SDHCI_TRANSFER_MODE)
+		shadow = newval;
+	else
+		bcm2835_sdhci_raw_writel(host, newval, reg & ~3);
+}
+
+static void bcm2835_sdhci_writeb(struct sdhci_host *host, u8 val, int reg)
+{
+	u32 oldval = bcm2835_sdhci_raw_readl(host, reg & ~3);
+	u32 byte_num = reg & 3;
+	u32 byte_shift = byte_num * 8;
+	u32 mask = 0xff << byte_shift;
+	u32 newval = (oldval & ~mask) | (val << byte_shift);
+
+	bcm2835_sdhci_raw_writel(host, newval, reg & ~3);
+}
+
+static u32 bcm2835_sdhci_readl(struct sdhci_host *host, int reg)
+{
+	u32 val = bcm2835_sdhci_raw_readl(host, reg);
+
+	return val;
+}
+
+static u16 bcm2835_sdhci_readw(struct sdhci_host *host, int reg)
+{
+	u32 val = bcm2835_sdhci_raw_readl(host, (reg & ~3));
+	u32 word_num = (reg >> 1) & 1;
+	u32 word_shift = word_num * 16;
+	u32 word = (val >> word_shift) & 0xffff;
+
+	return word;
+}
+
+static u8 bcm2835_sdhci_readb(struct sdhci_host *host, int reg)
+{
+	u32 val = bcm2835_sdhci_raw_readl(host, (reg & ~3));
+	u32 byte_num = reg & 3;
+	u32 byte_shift = byte_num * 8;
+	u32 byte = (val >> byte_shift) & 0xff;
+
+	return byte;
+}
+
+static const struct sdhci_ops bcm2835_ops = {
+	.write_l = bcm2835_sdhci_writel,
+	.write_w = bcm2835_sdhci_writew,
+	.write_b = bcm2835_sdhci_writeb,
+	.read_l = bcm2835_sdhci_readl,
+	.read_w = bcm2835_sdhci_readw,
+	.read_b = bcm2835_sdhci_readb,
+};
+
+int bcm2835_sdhci_init(u32 regbase, u32 emmc_freq)
+{
+	struct bcm2835_sdhci_host *bcm_host;
+	struct sdhci_host *host;
+
+	bcm_host = malloc(sizeof(*bcm_host));
+	if (!bcm_host) {
+		printf("sdhci_host malloc fail!\n");
+		return 1;
+	}
+
+	/*
+	 * See the comments in bcm2835_sdhci_raw_writel().
+	 *
+	 * This should probably be dynamically calculated based on the actual
+	 * frequency. However, this is the longest we'll have to wait, and
+	 * doesn't seem to slow access down too much, so the added complexity
+	 * doesn't seem worth it for now.
+	 *
+	 * 1/MIN_FREQ is (max) time per tick of eMMC clock.
+	 * 2/MIN_FREQ is time for two ticks.
+	 * Multiply by 1000000 to get uS per two ticks.
+	 * +1 for hack rounding.
+	 */
+	bcm_host->twoticks_delay = ((2 * 1000000) / MIN_FREQ) + 1;
+	bcm_host->last_write = 0;
+
+	host = &bcm_host->host;
+	host->name = "bcm2835_sdhci";
+	host->ioaddr = (void *)regbase;
+	host->quirks = SDHCI_QUIRK_BROKEN_VOLTAGE | SDHCI_QUIRK_BROKEN_R1B |
+		SDHCI_QUIRK_WAIT_SEND_CMD;
+	host->voltages = MMC_VDD_32_33 | MMC_VDD_33_34 | MMC_VDD_165_195;
+	host->ops = &bcm2835_ops;
+
+	host->version = sdhci_readw(host, SDHCI_HOST_VERSION);
+	add_sdhci(host, emmc_freq, MIN_FREQ);
+
+	return 0;
+}