bus: ti-sysc: Add support for PRUSS SYSC type

The PRU-ICSS present on AM33xx/AM43xx/AM57xx has a very unique
SYSCFG register. The register follows the OMAP4-style SYSC_TYPE3
for Master Standby and Slave Idle, but also has two additional
unique fields - STANDBY_INIT and SUB_MWAIT. The STANDBY_INIT is
a control bit that is used to initiate a Standby sequence (when
set) and trigger a MStandby request to the SoC's PRCM module. This
same bit is also used to enable the OCP master ports (when cleared)
to allow the PRU cores to access any peripherals or memory beyond
the PRU subsystem. The SUB_MWAIT is a ready status field for the
external access.

Add support for this SYSC type. The STANDBY_INIT has to be set
during suspend, without which it results in a hang in the resume
sequence on AM33xx/AM43xx boards and requires a board reset to
come out of the hang. Any PRU applications requiring external
access are supposed to clear the STANDBY_INIT bit. Note that
the PRUSS context is lost during a suspend sequence because the
PRUSS module is reset and/or disabled.
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
[tony@atomide.com: updated quirk define number and to use -ENODEV]
Signed-off-by: Tony Lindgren <tony@atomide.com>

drivers/bus/ti-sysc.c

@@ -1341,6 +1341,9 @@ static const struct sysc_revision_quirk sysc_revision_quirks[] = {
 		   SYSC_QUIRK_SWSUP_SIDLE | SYSC_QUIRK_SWSUP_MSTANDBY),
 	SYSC_QUIRK("wdt", 0, 0, 0x10, 0x14, 0x502a0500, 0xfffff0f0,
 		   SYSC_MODULE_QUIRK_WDT),
+	/* PRUSS on am3, am4 and am5 */
+	SYSC_QUIRK("pruss", 0, 0x26000, 0x26004, -ENODEV, 0x47000000, 0xff000000,
+		   SYSC_MODULE_QUIRK_PRUSS),
 	/* Watchdog on am3 and am4 */
 	SYSC_QUIRK("wdt", 0x44e35000, 0, 0x10, 0x14, 0x502a0500, 0xfffff0f0,
 		   SYSC_MODULE_QUIRK_WDT | SYSC_QUIRK_SWSUP_SIDLE),
@@ -1712,6 +1715,16 @@ static void sysc_reset_done_quirk_wdt(struct sysc *ddata)
 		dev_warn(ddata->dev, "wdt disable step2 failed\n");
 }
 
+/* PRUSS needs to set MSTANDBY_INIT inorder to idle properly */
+static void sysc_module_disable_quirk_pruss(struct sysc *ddata)
+{
+	u32 reg;
+
+	reg = sysc_read(ddata, ddata->offsets[SYSC_SYSCONFIG]);
+	reg |= SYSC_PRUSS_STANDBY_INIT;
+	sysc_write(ddata, ddata->offsets[SYSC_SYSCONFIG], reg);
+}
+
 static void sysc_init_module_quirks(struct sysc *ddata)
 {
 	if (ddata->legacy_mode || !ddata->name)
@@ -1750,6 +1763,9 @@ static void sysc_init_module_quirks(struct sysc *ddata)
 		ddata->reset_done_quirk = sysc_reset_done_quirk_wdt;
 		ddata->module_disable_quirk = sysc_reset_done_quirk_wdt;
 	}
+
+	if (ddata->cfg.quirks & SYSC_MODULE_QUIRK_PRUSS)
+		ddata->module_disable_quirk = sysc_module_disable_quirk_pruss;
 }
 
 static int sysc_clockdomain_init(struct sysc *ddata)
@@ -2555,6 +2571,16 @@ static const struct sysc_capabilities sysc_dra7_mcan = {
 	.mod_quirks = SYSS_QUIRK_RESETDONE_INVERTED,
 };
 
+/*
+ * PRUSS found on some AM33xx, AM437x and AM57xx SoCs
+ */
+static const struct sysc_capabilities sysc_pruss = {
+	.type = TI_SYSC_PRUSS,
+	.sysc_mask = SYSC_PRUSS_STANDBY_INIT | SYSC_PRUSS_SUB_MWAIT,
+	.regbits = &sysc_regbits_omap4_simple,
+	.mod_quirks = SYSC_MODULE_QUIRK_PRUSS,
+};
+
 static int sysc_init_pdata(struct sysc *ddata)
 {
 	struct ti_sysc_platform_data *pdata = dev_get_platdata(ddata->dev);
@@ -2936,6 +2962,7 @@ static const struct of_device_id sysc_match[] = {
 	{ .compatible = "ti,sysc-usb-host-fs",
 	  .data = &sysc_omap4_usb_host_fs, },
 	{ .compatible = "ti,sysc-dra7-mcan", .data = &sysc_dra7_mcan, },
+	{ .compatible = "ti,sysc-pruss", .data = &sysc_pruss, },
 	{  },
 };
 MODULE_DEVICE_TABLE(of, sysc_match);

include/linux/platform_data/ti-sysc.h

@@ -17,6 +17,7 @@ enum ti_sysc_module_type {
 	TI_SYSC_OMAP4_MCASP,
 	TI_SYSC_OMAP4_USB_HOST_FS,
 	TI_SYSC_DRA7_MCAN,
+	TI_SYSC_PRUSS,
 };
 
 struct ti_sysc_cookie {
@@ -49,6 +50,7 @@ struct sysc_regbits {
 	s8 emufree_shift;
 };
 
+#define SYSC_MODULE_QUIRK_PRUSS		BIT(24)
 #define SYSC_MODULE_QUIRK_DSS_RESET	BIT(23)
 #define SYSC_MODULE_QUIRK_RTC_UNLOCK	BIT(22)
 #define SYSC_QUIRK_CLKDM_NOAUTO		BIT(21)