pinctrl: sh-pfc: Add helper to handle bias lookup table

On some SoC there are no simple mapping of pins to bias register bits
and a lookup table is needed. This logic is already implemented in some
SoC specific drivers that could benefit from a generic implementation.

Add helpers to deal with the lookup which later can be used by the SoC
specific drivers. The logic used to lookup are different from the one it
aims to replace, this is intentional. This new method reduces the memory
consumption at the cost of increased CPU usage and fix a bug where a
WARN() would incorrectly be triggered if the register offset is 0.

Signed-off-by: Niklas Söderlund <[e-mail]>
Reviewed-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Geert Uytterhoeven <[e-mail]>

drivers/pinctrl/sh-pfc/core.c

···
 	return 0;
 }
 
+const struct sh_pfc_bias_info *
+sh_pfc_pin_to_bias_info(const struct sh_pfc_bias_info *info,
+			unsigned int num, unsigned int pin)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++)
+		if (info[i].pin == pin)
+			return &info[i];
+
+	WARN_ONCE(1, "Pin %u is not in bias info list\n", pin);
+
+	return NULL;
+}
+
 static int sh_pfc_init_ranges(struct sh_pfc *pfc)
 {
 	struct sh_pfc_pin_range *range;

drivers/pinctrl/sh-pfc/core.h

···
 int sh_pfc_get_pin_index(struct sh_pfc *pfc, unsigned int pin);
 int sh_pfc_config_mux(struct sh_pfc *pfc, unsigned mark, int pinmux_type);
 
+const struct sh_pfc_bias_info *
+sh_pfc_pin_to_bias_info(const struct sh_pfc_bias_info *info,
+			unsigned int num, unsigned int pin);
+
 #endif /* __SH_PFC_CORE_H__ */

drivers/pinctrl/sh-pfc/sh_pfc.h

···
 	unsigned long size;
 };
 
+struct sh_pfc_bias_info {
+	u16 pin;
+	u16 reg : 11;
+	u16 bit : 5;
+};
+
 struct sh_pfc_pin_range;
 
 struct sh_pfc {