mmc: add BCM2835 driver

Add a very simple driver for the BCM2835 SoC, which is used in the
Raspberry Pi board.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 227 insertions, 0 deletions

diff --git a/drivers/mmc/host/sdhci-bcm2835.c b/drivers/mmc/host/sdhci-bcm2835.c
new file mode 100644
index 000000000000..453825fcc5cf
--- /dev/null
+++ b/drivers/mmc/host/sdhci-bcm2835.c
@@ -0,0 +1,227 @@
+/*
+ * BCM2835 SDHCI
+ * Copyright (C) 2012 Stephen Warren
+ * Based on U-Boot's MMC driver for the BCM2835 by Oleksandr Tymoshenko & me
+ * 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.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/mmc/host.h>
+#include "sdhci-pltfm.h"
+
+/*
+ * 400KHz is max freq for card ID etc. Use that as min card clock. We need to
+ * know the min to enable static calculation of max BCM2835_SDHCI_WRITE_DELAY.
+ */
+#define MIN_FREQ 400000
+
+/*
+ * 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.
+ *
+ * This should probably be dynamically calculated based on the actual card
+ * 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.
+ * *1000000 for uSecs.
+ * +1 for hack rounding.
+ */
+#define BCM2835_SDHCI_WRITE_DELAY       (((2 * 1000000) / MIN_FREQ) + 1)
+
+struct bcm2835_sdhci {
+        struct clk *clk;
+        u32 shadow;
+};
+
+static void bcm2835_sdhci_writel(struct sdhci_host *host, u32 val, int reg)
+{
+        writel(val, host->ioaddr + reg);
+
+        udelay(BCM2835_SDHCI_WRITE_DELAY);
+}
+
+static inline u32 bcm2835_sdhci_readl(struct sdhci_host *host, int reg)
+{
+        u32 val = readl(host->ioaddr + reg);
+
+        if (reg == SDHCI_CAPABILITIES)
+                val |= SDHCI_CAN_VDD_330;
+
+        return val;
+}
+
+static void bcm2835_sdhci_writew(struct sdhci_host *host, u16 val, int reg)
+{
+        struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+        struct bcm2835_sdhci *bcm2835_host = pltfm_host->priv;
+        u32 oldval = (reg == SDHCI_COMMAND) ? bcm2835_host->shadow :
+                bcm2835_sdhci_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)
+                bcm2835_host->shadow = newval;
+        else
+                bcm2835_sdhci_writel(host, newval, reg & ~3);
+}
+
+static u16 bcm2835_sdhci_readw(struct sdhci_host *host, int reg)
+{
+        u32 val = bcm2835_sdhci_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 void bcm2835_sdhci_writeb(struct sdhci_host *host, u8 val, int reg)
+{
+        u32 oldval = bcm2835_sdhci_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_writel(host, newval, reg & ~3);
+}
+
+static u8 bcm2835_sdhci_readb(struct sdhci_host *host, int reg)
+{
+        u32 val = bcm2835_sdhci_readl(host, (reg & ~3));
+        u32 byte_num = reg & 3;
+        u32 byte_shift = byte_num * 8;
+        u32 byte = (val >> byte_shift) & 0xff;
+
+        return byte;
+}
+
+static unsigned int bcm2835_sdhci_get_max_clock(struct sdhci_host *host)
+{
+        struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+        struct bcm2835_sdhci *bcm2835_host = pltfm_host->priv;
+
+        return clk_get_rate(bcm2835_host->clk);
+}
+
+unsigned int bcm2835_sdhci_get_min_clock(struct sdhci_host *host)
+{
+        return MIN_FREQ;
+}
+
+unsigned int bcm2835_sdhci_get_timeout_clock(struct sdhci_host *host)
+{
+        struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+        struct bcm2835_sdhci *bcm2835_host = pltfm_host->priv;
+
+        return clk_get_rate(bcm2835_host->clk);
+}
+
+static struct sdhci_ops bcm2835_sdhci_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,
+        .get_max_clock = bcm2835_sdhci_get_max_clock,
+        .get_min_clock = bcm2835_sdhci_get_min_clock,
+        .get_timeout_clock = bcm2835_sdhci_get_timeout_clock,
+};
+
+static struct sdhci_pltfm_data bcm2835_sdhci_pdata = {
+        .quirks = SDHCI_QUIRK_BROKEN_CARD_DETECTION,
+        .ops = &bcm2835_sdhci_ops,
+};
+
+static int bcm2835_sdhci_probe(struct platform_device *pdev)
+{
+        struct sdhci_host *host;
+        struct bcm2835_sdhci *bcm2835_host;
+        struct sdhci_pltfm_host *pltfm_host;
+        int ret;
+
+        host = sdhci_pltfm_init(pdev, &bcm2835_sdhci_pdata);
+        if (IS_ERR(host))
+                return PTR_ERR(host);
+
+        bcm2835_host = devm_kzalloc(&pdev->dev, sizeof(*bcm2835_host),
+                                        GFP_KERNEL);
+        if (!bcm2835_host) {
+                dev_err(mmc_dev(host->mmc),
+                        "failed to allocate bcm2835_sdhci\n");
+                return -ENOMEM;
+        }
+
+        pltfm_host = sdhci_priv(host);
+        pltfm_host->priv = bcm2835_host;
+
+        bcm2835_host->clk = devm_clk_get(&pdev->dev, NULL);
+        if (IS_ERR(bcm2835_host->clk)) {
+                ret = PTR_ERR(bcm2835_host->clk);
+                goto err;
+        }
+
+        return sdhci_add_host(host);
+
+err:
+        sdhci_pltfm_free(pdev);
+        return ret;
+}
+
+static int bcm2835_sdhci_remove(struct platform_device *pdev)
+{
+        struct sdhci_host *host = platform_get_drvdata(pdev);
+        int dead = (readl(host->ioaddr + SDHCI_INT_STATUS) == 0xffffffff);
+
+        sdhci_remove_host(host, dead);
+        sdhci_pltfm_free(pdev);
+
+        return 0;
+}
+
+static const struct of_device_id bcm2835_sdhci_of_match[] = {
+        { .compatible = "brcm,bcm2835-sdhci" },
+        { }
+};
+MODULE_DEVICE_TABLE(of, bcm2835_sdhci_of_match);
+
+static struct platform_driver bcm2835_sdhci_driver = {
+        .driver = {
+                .name = "sdhci-bcm2835",
+                .owner = THIS_MODULE,
+                .of_match_table = bcm2835_sdhci_of_match,
+                .pm = SDHCI_PLTFM_PMOPS,
+        },
+        .probe = bcm2835_sdhci_probe,
+        .remove = bcm2835_sdhci_remove,
+};
+module_platform_driver(bcm2835_sdhci_driver);
+
+MODULE_DESCRIPTION("BCM2835 SDHCI driver");
+MODULE_AUTHOR("Stephen Warren");
+MODULE_LICENSE("GPL v2");