[PATCH v4 4/7] remoteproc: mtk_apu: Add support of JTAG

[Alexandre Bailon <abailon@baylibre.com>]

The DSP could be debugged using JTAG.
The support of JTAG could enabled at build time and it could be enabled
using debugfs.

Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
---
 drivers/remoteproc/Kconfig   |   9 +++
 drivers/remoteproc/mtk_apu.c | 147 ++++++++++++++++++++++++++++++++++-
 2 files changed, 155 insertions(+), 1 deletion(-)

diff --git a/drivers/remoteproc/Kconfig b/drivers/remoteproc/Kconfig
index 959d24e9492c..28140cf04d8a 100644
--- a/drivers/remoteproc/Kconfig
+++ b/drivers/remoteproc/Kconfig
@@ -74,6 +74,15 @@ config MTK_APU
 
 	  It's safe to say N here.
 
+config MTK_APU_JTAG
+	bool "Enable support of JTAG"
+	depends on MTK_APU
+	help
+	  Say y to enable support of JTAG.
+	  By default, JTAG will remain disabled until it is enabled using
+	  debugfs: remoteproc/remoteproc0/jtag. Write 1 to enable it and
+	  0 to disable it.
+
 config OMAP_REMOTEPROC
 	tristate "OMAP remoteproc support"
 	depends on ARCH_OMAP4 || SOC_OMAP5 || SOC_DRA7XX
diff --git a/drivers/remoteproc/mtk_apu.c b/drivers/remoteproc/mtk_apu.c
index 867b4682b507..3905eb5b7174 100644
--- a/drivers/remoteproc/mtk_apu.c
+++ b/drivers/remoteproc/mtk_apu.c
@@ -5,12 +5,14 @@
 
 #include <linux/bitops.h>
 #include <linux/clk.h>
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/iommu.h>
 #include <linux/irq.h>
 #include <linux/module.h>
 #include <linux/of_reserved_mem.h>
+#include <linux/pinctrl/consumer.h>
 #include <linux/platform_device.h>
 #include <linux/remoteproc.h>
 #include <linux/string.h>
@@ -45,6 +47,11 @@
 #define CORE_DEFAULT1				(0x00000140)
 #define CORE_DEFAULT0_ARUSER_IDMA_USE_IOMMU	(0x10 << 0)
 #define CORE_DEFAULT0_AWUSER_IDMA_USE_IOMMU	(0x10 << 5)
+#define CORE_DEFAULT2				(0x00000144)
+#define CORE_DEFAULT2_DBG_EN			BIT(3)
+#define CORE_DEFAULT2_NIDEN			BIT(2)
+#define CORE_DEFAULT2_SPNIDEN			BIT(1)
+#define CORE_DEFAULT2_SPIDEN			BIT(0)
 #define CORE_XTENSA_ALTRESETVEC			(0x000001F8)
 
 #define VDEV_MEM_COUNT				(3)
@@ -59,6 +66,13 @@ struct mtk_apu_rproc {
 	struct clk_bulk_data *clks;
 	struct iommu_domain *domain;
 	struct list_head mappings;
+
+#ifdef CONFIG_MTK_APU_JTAG
+	struct pinctrl *pinctrl;
+	struct pinctrl_state *pinctrl_jtag;
+	bool jtag_enabled;
+	struct mutex jtag_mutex;
+#endif
 };
 
 static const char * const mt8183_clk_names[] = {
@@ -355,6 +369,133 @@ static irqreturn_t mtk_apu_rproc_callback(int irq, void *data)
 	return IRQ_WAKE_THREAD;
 }
 
+#ifdef CONFIG_MTK_APU_JTAG
+
+static int apu_enable_jtag(struct mtk_apu_rproc *apu_rproc)
+{
+	int ret = 0;
+
+	mutex_lock(&apu_rproc->jtag_mutex);
+	if (apu_rproc->jtag_enabled)
+		goto err_mutex_unlock;
+
+	writel(CORE_DEFAULT2_SPNIDEN | CORE_DEFAULT2_SPIDEN |
+		CORE_DEFAULT2_NIDEN | CORE_DEFAULT2_DBG_EN,
+		apu_rproc->base + CORE_DEFAULT2);
+
+	apu_rproc->jtag_enabled = 1;
+
+err_mutex_unlock:
+	mutex_unlock(&apu_rproc->jtag_mutex);
+
+	return ret;
+}
+
+static int apu_disable_jtag(struct mtk_apu_rproc *apu_rproc)
+{
+	int ret = 0;
+
+	mutex_lock(&apu_rproc->jtag_mutex);
+	if (!apu_rproc->jtag_enabled)
+		goto err_mutex_unlock;
+
+	writel(0, apu_rproc->base + CORE_DEFAULT2);
+
+	apu_rproc->jtag_enabled = 0;
+
+err_mutex_unlock:
+	mutex_unlock(&apu_rproc->jtag_mutex);
+
+	return ret;
+}
+
+static ssize_t rproc_jtag_read(struct file *filp, char __user *userbuf,
+			       size_t count, loff_t *ppos)
+{
+	struct rproc *rproc = filp->private_data;
+	struct mtk_apu_rproc *apu_rproc = (struct mtk_apu_rproc *)rproc->priv;
+	char *buf = apu_rproc->jtag_enabled ? "enabled\n" : "disabled\n";
+
+	return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf));
+}
+
+static ssize_t rproc_jtag_write(struct file *filp, const char __user *user_buf,
+				size_t count, loff_t *ppos)
+{
+	struct rproc *rproc = filp->private_data;
+	struct mtk_apu_rproc *apu_rproc = (struct mtk_apu_rproc *)rproc->priv;
+	char buf[10];
+	int ret;
+
+	if (count < 1 || count > sizeof(buf))
+		return -EINVAL;
+
+	ret = copy_from_user(buf, user_buf, count);
+	if (ret)
+		return -EFAULT;
+
+	/* remove end of line */
+	if (buf[count - 1] == '\n')
+		buf[count - 1] = '\0';
+
+	if (!strncmp(buf, "enabled", count))
+		ret = apu_enable_jtag(apu_rproc);
+	else if (!strncmp(buf, "disabled", count))
+		ret = apu_disable_jtag(apu_rproc);
+	else
+		return -EINVAL;
+
+	return ret ? ret : count;
+}
+
+static const struct file_operations rproc_jtag_ops = {
+	.read = rproc_jtag_read,
+	.write = rproc_jtag_write,
+	.open = simple_open,
+};
+
+static int apu_jtag_probe(struct mtk_apu_rproc *apu_rproc)
+{
+	int ret;
+
+	if (!apu_rproc->rproc->dbg_dir)
+		return -ENODEV;
+
+	apu_rproc->pinctrl = devm_pinctrl_get(apu_rproc->dev);
+	if (IS_ERR(apu_rproc->pinctrl)) {
+		dev_warn(apu_rproc->dev, "Failed to find JTAG pinctrl\n");
+		return PTR_ERR(apu_rproc->pinctrl);
+	}
+
+	apu_rproc->pinctrl_jtag = pinctrl_lookup_state(apu_rproc->pinctrl,
+						       "jtag");
+	if (IS_ERR(apu_rproc->pinctrl_jtag))
+		return PTR_ERR(apu_rproc->pinctrl_jtag);
+
+	ret = pinctrl_select_state(apu_rproc->pinctrl,
+				   apu_rproc->pinctrl_jtag);
+	if (ret < 0)
+		return ret;
+
+	mutex_init(&apu_rproc->jtag_mutex);
+
+	debugfs_create_file("jtag", 0600, apu_rproc->rproc->dbg_dir,
+			    apu_rproc->rproc, &rproc_jtag_ops);
+
+	return 0;
+}
+#else
+static int apu_jtag_probe(struct mtk_apu_rproc *apu_rproc)
+{
+	return 0;
+}
+
+static int apu_disable_jtag(struct mtk_apu_rproc *apu_rproc)
+{
+	return 0;
+}
+#endif /* CONFIG_MTK_APU_JTAG */
+
 static int mtk_apu_rproc_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -442,6 +583,10 @@ static int mtk_apu_rproc_probe(struct platform_device *pdev)
 		goto free_rproc;
 	}
 
+	ret = apu_jtag_probe(apu_rproc);
+	if (ret)
+		dev_warn(dev, "Failed to configure jtag\n");
+
 	return 0;
 
 free_rproc:
@@ -457,7 +602,7 @@ static int mtk_apu_rproc_remove(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 
 	disable_irq(apu_rproc->irq);
-
+	apu_disable_jtag(apu_rproc);
 	rproc_del(rproc);
 	of_reserved_mem_device_release(dev);
 	rproc_free(rproc);
-- 
2.34.1