ARM: socfpga: fpga bridge driver support

Supports Altera SOCFPGA bridges:
 * fpga2sdram
 * fpga2hps
 * hps2fpga
 * lwhps2fpga

Allows enabling/disabling the bridges through the FPGA
Bridge Framework API functions.

The fpga2sdram driver only supports enabling and disabling
of the ports that been configured early on.  This is due to
a hardware limitation where the read, write, and command
ports on the fpga2sdram bridge can only be reconfigured
while there are no transactions to the sdram, i.e. when
running out of OCRAM before the kernel boots.

Device tree property 'init-val' configures the driver to
enable or disable the bridge during probe.  If the property
does not exist, the driver will leave the bridge in its
current state.

Signed-off-by: Alan Tull <atull@opensource.altera.com>
Signed-off-by: Matthew Gerlach <mgerlach@altera.com>
Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 222 insertions, 0 deletions

diff --git a/drivers/fpga/altera-hps2fpga.c b/drivers/fpga/altera-hps2fpga.c
new file mode 100644
index 000000000000..4b354c79be31
--- /dev/null
+++ b/drivers/fpga/altera-hps2fpga.c
@@ -0,0 +1,222 @@
+/*
+ * FPGA to/from HPS Bridge Driver for Altera SoCFPGA Devices
+ *
+ *  Copyright (C) 2013-2016 Altera Corporation, All Rights Reserved.
+ *
+ * Includes this patch from the mailing list:
+ *   fpga: altera-hps2fpga: fix HPS2FPGA bridge visibility to L3 masters
+ *   Signed-off-by: Anatolij Gustschin <agust@denx.de>
+ *
+ * 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/>.
+ */
+
+/*
+ * This driver manages bridges on a Altera SOCFPGA between the ARM host
+ * processor system (HPS) and the embedded FPGA.
+ *
+ * This driver supports enabling and disabling of the configured ports, which
+ * allows for safe reprogramming of the FPGA, assuming that the new FPGA image
+ * uses the same port configuration.  Bridges must be disabled before
+ * reprogramming the FPGA and re-enabled after the FPGA has been programmed.
+ */
+
+#include <linux/clk.h>
+#include <linux/fpga/fpga-bridge.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/regmap.h>
+#include <linux/reset.h>
+#include <linux/spinlock.h>
+
+#define ALT_L3_REMAP_OFST                       0x0
+#define ALT_L3_REMAP_MPUZERO_MSK                0x00000001
+#define ALT_L3_REMAP_H2F_MSK                    0x00000008
+#define ALT_L3_REMAP_LWH2F_MSK                  0x00000010
+
+#define HPS2FPGA_BRIDGE_NAME                    "hps2fpga"
+#define LWHPS2FPGA_BRIDGE_NAME                  "lwhps2fpga"
+#define FPGA2HPS_BRIDGE_NAME                    "fpga2hps"
+
+struct altera_hps2fpga_data {
+        const char *name;
+        struct reset_control *bridge_reset;
+        struct regmap *l3reg;
+        unsigned int remap_mask;
+        struct clk *clk;
+};
+
+static int alt_hps2fpga_enable_show(struct fpga_bridge *bridge)
+{
+        struct altera_hps2fpga_data *priv = bridge->priv;
+
+        return reset_control_status(priv->bridge_reset);
+}
+
+/* The L3 REMAP register is write only, so keep a cached value. */
+static unsigned int l3_remap_shadow;
+static spinlock_t l3_remap_lock;
+
+static int _alt_hps2fpga_enable_set(struct altera_hps2fpga_data *priv,
+                                    bool enable)
+{
+        unsigned long flags;
+        int ret;
+
+        /* bring bridge out of reset */
+        if (enable)
+                ret = reset_control_deassert(priv->bridge_reset);
+        else
+                ret = reset_control_assert(priv->bridge_reset);
+        if (ret)
+                return ret;
+
+        /* Allow bridge to be visible to L3 masters or not */
+        if (priv->remap_mask) {
+                spin_lock_irqsave(&l3_remap_lock, flags);
+                l3_remap_shadow |= ALT_L3_REMAP_MPUZERO_MSK;
+
+                if (enable)
+                        l3_remap_shadow |= priv->remap_mask;
+                else
+                        l3_remap_shadow &= ~priv->remap_mask;
+
+                ret = regmap_write(priv->l3reg, ALT_L3_REMAP_OFST,
+                                   l3_remap_shadow);
+                spin_unlock_irqrestore(&l3_remap_lock, flags);
+        }
+
+        return ret;
+}
+
+static int alt_hps2fpga_enable_set(struct fpga_bridge *bridge, bool enable)
+{
+        return _alt_hps2fpga_enable_set(bridge->priv, enable);
+}
+
+static const struct fpga_bridge_ops altera_hps2fpga_br_ops = {
+        .enable_set = alt_hps2fpga_enable_set,
+        .enable_show = alt_hps2fpga_enable_show,
+};
+
+static struct altera_hps2fpga_data hps2fpga_data  = {
+        .name = HPS2FPGA_BRIDGE_NAME,
+        .remap_mask = ALT_L3_REMAP_H2F_MSK,
+};
+
+static struct altera_hps2fpga_data lwhps2fpga_data  = {
+        .name = LWHPS2FPGA_BRIDGE_NAME,
+        .remap_mask = ALT_L3_REMAP_LWH2F_MSK,
+};
+
+static struct altera_hps2fpga_data fpga2hps_data  = {
+        .name = FPGA2HPS_BRIDGE_NAME,
+};
+
+static const struct of_device_id altera_fpga_of_match[] = {
+        { .compatible = "altr,socfpga-hps2fpga-bridge",
+          .data = &hps2fpga_data },
+        { .compatible = "altr,socfpga-lwhps2fpga-bridge",
+          .data = &lwhps2fpga_data },
+        { .compatible = "altr,socfpga-fpga2hps-bridge",
+          .data = &fpga2hps_data },
+        {},
+};
+
+static int alt_fpga_bridge_probe(struct platform_device *pdev)
+{
+        struct device *dev = &pdev->dev;
+        struct altera_hps2fpga_data *priv;
+        const struct of_device_id *of_id;
+        u32 enable;
+        int ret;
+
+        of_id = of_match_device(altera_fpga_of_match, dev);
+        priv = (struct altera_hps2fpga_data *)of_id->data;
+
+        priv->bridge_reset = of_reset_control_get_by_index(dev->of_node, 0);
+        if (IS_ERR(priv->bridge_reset)) {
+                dev_err(dev, "Could not get %s reset control\n", priv->name);
+                return PTR_ERR(priv->bridge_reset);
+        }
+
+        if (priv->remap_mask) {
+                priv->l3reg = syscon_regmap_lookup_by_compatible("altr,l3regs");
+                if (IS_ERR(priv->l3reg)) {
+                        dev_err(dev, "regmap for altr,l3regs lookup failed\n");
+                        return PTR_ERR(priv->l3reg);
+                }
+        }
+
+        priv->clk = devm_clk_get(dev, NULL);
+        if (IS_ERR(priv->clk)) {
+                dev_err(dev, "no clock specified\n");
+                return PTR_ERR(priv->clk);
+        }
+
+        ret = clk_prepare_enable(priv->clk);
+        if (ret) {
+                dev_err(dev, "could not enable clock\n");
+                return -EBUSY;
+        }
+
+        spin_lock_init(&l3_remap_lock);
+
+        if (!of_property_read_u32(dev->of_node, "bridge-enable", &enable)) {
+                if (enable > 1) {
+                        dev_warn(dev, "invalid bridge-enable %u > 1\n", enable);
+                } else {
+                        dev_info(dev, "%s bridge\n",
+                                 (enable ? "enabling" : "disabling"));
+
+                        ret = _alt_hps2fpga_enable_set(priv, enable);
+                        if (ret) {
+                                fpga_bridge_unregister(&pdev->dev);
+                                return ret;
+                        }
+                }
+        }
+
+        return fpga_bridge_register(dev, priv->name, &altera_hps2fpga_br_ops,
+                                    priv);
+}
+
+static int alt_fpga_bridge_remove(struct platform_device *pdev)
+{
+        struct fpga_bridge *bridge = platform_get_drvdata(pdev);
+        struct altera_hps2fpga_data *priv = bridge->priv;
+
+        fpga_bridge_unregister(&pdev->dev);
+
+        clk_disable_unprepare(priv->clk);
+
+        return 0;
+}
+
+MODULE_DEVICE_TABLE(of, altera_fpga_of_match);
+
+static struct platform_driver alt_fpga_bridge_driver = {
+        .probe = alt_fpga_bridge_probe,
+        .remove = alt_fpga_bridge_remove,
+        .driver = {
+                .name   = "altera_hps2fpga_bridge",
+                .of_match_table = of_match_ptr(altera_fpga_of_match),
+        },
+};
+
+module_platform_driver(alt_fpga_bridge_driver);
+
+MODULE_DESCRIPTION("Altera SoCFPGA HPS to FPGA Bridge");
+MODULE_AUTHOR("Alan Tull <atull@opensource.altera.com>");
+MODULE_LICENSE("GPL v2");