bus: ti-sysc: Add support for software reset

Add support for the software reset of a target interconnect
module using its sysconfig and sysstatus registers.
Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
[tony@atomide.com: updated to check if sysconfig exists]
Signed-off-by: Tony Lindgren <tony@atomide.com>

drivers/bus/ti-sysc.c

@@ -23,11 +23,14 @@
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/slab.h>
+#include <linux/iopoll.h>
 
 #include <linux/platform_data/ti-sysc.h>
 
 #include <dt-bindings/bus/ti-sysc.h>
 
+#define MAX_MODULE_SOFTRESET_WAIT		10000
+
 static const char * const reg_names[] = { "rev", "sysc", "syss", };
 
 enum sysc_clocks {
@@ -88,6 +91,11 @@ struct sysc {
 	struct delayed_work idle_work;
 };
 
+void sysc_write(struct sysc *ddata, int offset, u32 value)
+{
+	writel_relaxed(value, ddata->module_va + offset);
+}
+
 static u32 sysc_read(struct sysc *ddata, int offset)
 {
 	if (ddata->cfg.quirks & SYSC_QUIRK_16BIT) {
@@ -943,6 +951,36 @@ static void sysc_init_revision_quirks(struct sysc *ddata)
 	}
 }
 
+static int sysc_reset(struct sysc *ddata)
+{
+	int offset = ddata->offsets[SYSC_SYSCONFIG];
+	int val;
+
+	if (ddata->legacy_mode || offset < 0 ||
+	    ddata->cfg.quirks & SYSC_QUIRK_NO_RESET_ON_INIT)
+		return 0;
+
+	/*
+	 * Currently only support reset status in sysstatus.
+	 * Warn and return error in all other cases
+	 */
+	if (!ddata->cfg.syss_mask) {
+		dev_err(ddata->dev, "No ti,syss-mask. Reset failed\n");
+		return -EINVAL;
+	}
+
+	val = sysc_read(ddata, offset);
+	val |= (0x1 << ddata->cap->regbits->srst_shift);
+	sysc_write(ddata, offset, val);
+
+	/* Poll on reset status */
+	offset = ddata->offsets[SYSC_SYSSTATUS];
+
+	return readl_poll_timeout(ddata->module_va + offset, val,
+				  (val & ddata->cfg.syss_mask) == 0x0,
+				  100, MAX_MODULE_SOFTRESET_WAIT);
+}
+
 /* At this point the module is configured enough to read the revision */
 static int sysc_init_module(struct sysc *ddata)
 {
@@ -960,6 +998,14 @@ static int sysc_init_module(struct sysc *ddata)
 		return 0;
 	}
 
+	error = sysc_reset(ddata);
+	if (error) {
+		dev_err(ddata->dev, "Reset failed with %d\n", error);
+		pm_runtime_put_sync(ddata->dev);
+
+		return error;
+	}
+
 	ddata->revision = sysc_read_revision(ddata);
 	pm_runtime_put_sync(ddata->dev);