soc: fsl: handle RCPM errata A-008646 on SoC LS1021A

Hardware issue:
- Reading register RCPM_IPPDEXPCR1 always return zero, this causes
  system firmware could not get correct information and wrongly do
  clock gating for all wakeup source IP during system suspend. Then
  those IPs will never get chance to wake system.

Workaround:
- Copy register RCPM_IPPDEXPCR1's setting to register SCFG_SPARECR8
  to allow system firmware's psci method read it and do things accordingly.
Signed-off-by: Biwen Li <biwen.li@nxp.com>
Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>

drivers/soc/fsl/rcpm.c

@@ -2,7 +2,7 @@
 //
 // rcpm.c - Freescale QorIQ RCPM driver
 //
-// Copyright 2019 NXP
+// Copyright 2019-2020 NXP
 //
 // Author: Ran Wang <ran.wang_1@nxp.com>
 
@@ -22,6 +22,28 @@ struct rcpm {
 	bool		little_endian;
 };
 
+#define  SCFG_SPARECR8	0x051c
+
+static void copy_ippdexpcr1_setting(u32 val)
+{
+	struct device_node *np;
+	void __iomem *regs;
+	u32 reg_val;
+
+	np = of_find_compatible_node(NULL, NULL, "fsl,ls1021a-scfg");
+	if (!np)
+		return;
+
+	regs = of_iomap(np, 0);
+	if (!regs)
+		return;
+
+	reg_val = ioread32be(regs + SCFG_SPARECR8);
+	iowrite32be(val | reg_val, regs + SCFG_SPARECR8);
+
+	iounmap(regs);
+}
+
 /**
  * rcpm_pm_prepare - performs device-level tasks associated with power
  * management, such as programming related to the wakeup source control.
@@ -90,6 +112,17 @@ static int rcpm_pm_prepare(struct device *dev)
 			tmp |= ioread32be(address);
 			iowrite32be(tmp, address);
 		}
+		/*
+		 * Workaround of errata A-008646 on SoC LS1021A:
+		 * There is a bug of register ippdexpcr1.
+		 * Reading configuration register RCPM_IPPDEXPCR1
+		 * always return zero. So save ippdexpcr1's value
+		 * to register SCFG_SPARECR8.And the value of
+		 * ippdexpcr1 will be read from SCFG_SPARECR8.
+		 */
+		if (dev_of_node(dev) && (i == 1))
+			if (of_device_is_compatible(np, "fsl,ls1021a-rcpm"))
+				copy_ippdexpcr1_setting(tmp);
 	}
 
 	return 0;