soc: ixp4xx-npe: Access syscon regs using regmap

If we access the syscon (expansion bus config registers) using the
syscon regmap instead of relying on direct accessor functions,
we do not need to call this static code in the machine
(arch/arm/mach-ixp4xx/common.c) which makes things less dependent
on custom machine-dependent code.

Look up the syscon regmap and handle the error: this will make
deferred probe work with relation to the syscon.

Signed-off-by: Linus Walleij <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Linus Walleij <[e-mail]>

drivers/soc/ixp4xx/Kconfig

···
 config IXP4XX_NPE
 	tristate "IXP4xx Network Processor Engine support"
 	select FW_LOADER
+	select MFD_SYSCON
 	help
 	  This driver supports IXP4xx built-in network coprocessors
 	  and is automatically selected by Ethernet and HSS drivers.

drivers/soc/ixp4xx/ixp4xx-npe.c

···
 #include <linux/firmware.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_platform.h>
···
 
 static int npe_reset(struct npe *npe)
 {
+	u32 reset_bit = (IXP4XX_FEATURE_RESET_NPEA << npe->id);
 	u32 val, ctl, exec_count, ctx_reg2;
 	int i;
 
···
 	__raw_writel(0, &npe->regs->action_points[3]);
 	__raw_writel(0, &npe->regs->watch_count);
 
-	val = ixp4xx_read_feature_bits();
+	/*
+	 * We need to work on cached values here because the register
+	 * will read inverted but needs to be written non-inverted.
+	 */
+	val = cpu_ixp4xx_features(npe->rmap);
 	/* reset the NPE */
-	ixp4xx_write_feature_bits(val &
-				  ~(IXP4XX_FEATURE_RESET_NPEA << npe->id));
+	regmap_write(npe->rmap, IXP4XX_EXP_CNFG2, val & ~reset_bit);
 	/* deassert reset */
-	ixp4xx_write_feature_bits(val |
-				  (IXP4XX_FEATURE_RESET_NPEA << npe->id));
+	regmap_write(npe->rmap, IXP4XX_EXP_CNFG2, val | reset_bit);
+
 	for (i = 0; i < MAX_RETRIES; i++) {
-		if (ixp4xx_read_feature_bits() &
-		    (IXP4XX_FEATURE_RESET_NPEA << npe->id))
+		val = cpu_ixp4xx_features(npe->rmap);
+		if (val & reset_bit)
 			break;	/* NPE is back alive */
 		udelay(1);
 	}
···
 	struct device *dev = &pdev->dev;
 	struct device_node *np = dev->of_node;
 	struct resource *res;
+	struct regmap *rmap;
+	u32 val;
+
+	/* This system has only one syscon, so fetch it */
+	rmap = syscon_regmap_lookup_by_compatible("syscon");
+	if (IS_ERR(rmap))
+		return dev_err_probe(dev, PTR_ERR(rmap),
+				     "failed to look up syscon\n");
 
 	for (i = 0; i < NPE_COUNT; i++) {
 		struct npe *npe = &npe_tab[i];
···
 		if (!res)
 			return -ENODEV;
 
-		if (!(ixp4xx_read_feature_bits() &
-		      (IXP4XX_FEATURE_RESET_NPEA << i))) {
+		val = cpu_ixp4xx_features(rmap);
+
+		if (!(val & (IXP4XX_FEATURE_RESET_NPEA << i))) {
 			dev_info(dev, "NPE%d at %pR not available\n",
 				 i, res);
 			continue; /* NPE already disabled or not present */
···
 		npe->regs = devm_ioremap_resource(dev, res);
 		if (IS_ERR(npe->regs))
 			return PTR_ERR(npe->regs);
+		npe->rmap = rmap;
 
 		if (npe_reset(npe)) {
 			dev_info(dev, "NPE%d at %pR does not reset\n",

include/linux/soc/ixp4xx/npe.h

···
 #define __IXP4XX_NPE_H
 
 #include <linux/kernel.h>
+#include <linux/regmap.h>
 
 extern const char *npe_names[];
 
···
 
 struct npe {
 	struct npe_regs __iomem *regs;
+	struct regmap *rmap;
 	int id;
 	int valid;
 };