thermal/drivers/rcar_gen3: Move Tj_T storage to shared private data

The calculated Tj_T constant is calculated from the PTAT data either
read from the first TSC zone on the device if calibration data is fused,
or from fallback values in the driver itself. The value calculated is
shared among all TSC zones.

Move the Tj_T constant to the shared private data structure instead of
duplicating it in each TSC private data. This requires adding a pointer
to the shared data to the TSC private data structure. This back pointer
make it easier to further rework the temperature conversion logic.
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20240327133013.3982199-2-niklas.soderlund+renesas@ragnatech.se

drivers/thermal/rcar_gen3_thermal.c

@@ -81,10 +81,10 @@ struct rcar_thermal_info {
 };
 
 struct rcar_gen3_thermal_tsc {
+	struct rcar_gen3_thermal_priv *priv;
 	void __iomem *base;
 	struct thermal_zone_device *zone;
 	struct equation_coefs coef;
-	int tj_t;
 	int thcode[3];
 };
 
@@ -93,6 +93,7 @@ struct rcar_gen3_thermal_priv {
 	struct thermal_zone_device_ops ops;
 	unsigned int num_tscs;
 	int ptat[3];
+	int tj_t;
 	const struct rcar_thermal_info *info;
 };
 
@@ -136,26 +137,32 @@ static inline void rcar_gen3_thermal_write(struct rcar_gen3_thermal_tsc *tsc,
 /* no idea where these constants come from */
 #define TJ_3 -41
 
-static void rcar_gen3_thermal_calc_coefs(struct rcar_gen3_thermal_priv *priv,
-					 struct rcar_gen3_thermal_tsc *tsc,
-					 int ths_tj_1)
+static void rcar_gen3_thermal_shared_coefs(struct rcar_gen3_thermal_priv *priv)
+{
+	int tj1 = priv->info->ths_tj_1;
+
+	priv->tj_t = (FIXPT_INT((priv->ptat[1] - priv->ptat[2]) * (tj1 - TJ_3))
+		      / (priv->ptat[0] - priv->ptat[2])) + FIXPT_INT(TJ_3);
+}
+
+static void rcar_gen3_thermal_tsc_coefs(struct rcar_gen3_thermal_priv *priv,
+					struct rcar_gen3_thermal_tsc *tsc)
 {
+	int tj1 = priv->info->ths_tj_1;
+
 	/* TODO: Find documentation and document constant calculation formula */
 
 	/*
 	 * Division is not scaled in BSP and if scaled it might overflow
 	 * the dividend (4095 * 4095 << 14 > INT_MAX) so keep it unscaled
 	 */
-	tsc->tj_t = (FIXPT_INT((priv->ptat[1] - priv->ptat[2]) * (ths_tj_1 - TJ_3))
-		     / (priv->ptat[0] - priv->ptat[2])) + FIXPT_INT(TJ_3);
-
 	tsc->coef.a1 = FIXPT_DIV(FIXPT_INT(tsc->thcode[1] - tsc->thcode[2]),
-				 tsc->tj_t - FIXPT_INT(TJ_3));
+				 priv->tj_t - FIXPT_INT(TJ_3));
 	tsc->coef.b1 = FIXPT_INT(tsc->thcode[2]) - tsc->coef.a1 * TJ_3;
 
 	tsc->coef.a2 = FIXPT_DIV(FIXPT_INT(tsc->thcode[1] - tsc->thcode[0]),
-				 tsc->tj_t - FIXPT_INT(ths_tj_1));
-	tsc->coef.b2 = FIXPT_INT(tsc->thcode[0]) - tsc->coef.a2 * ths_tj_1;
+				 priv->tj_t - FIXPT_INT(tj1));
+	tsc->coef.b2 = FIXPT_INT(tsc->thcode[0]) - tsc->coef.a2 * tj1;
 }
 
 static int rcar_gen3_thermal_round(int temp)
@@ -196,10 +203,11 @@ static int rcar_gen3_thermal_get_temp(struct thermal_zone_device *tz, int *temp)
 static int rcar_gen3_thermal_mcelsius_to_temp(struct rcar_gen3_thermal_tsc *tsc,
 					      int mcelsius)
 {
+	struct rcar_gen3_thermal_priv *priv = tsc->priv;
 	int celsius, val;
 
 	celsius = DIV_ROUND_CLOSEST(mcelsius, 1000);
-	if (celsius <= INT_FIXPT(tsc->tj_t))
+	if (celsius <= INT_FIXPT(priv->tj_t))
 		val = celsius * tsc->coef.a1 + tsc->coef.b1;
 	else
 		val = celsius * tsc->coef.a2 + tsc->coef.b2;
@@ -516,6 +524,7 @@ static int rcar_gen3_thermal_probe(struct platform_device *pdev)
 			goto error_unregister;
 		}
 
+		tsc->priv = priv;
 		tsc->base = devm_ioremap_resource(dev, res);
 		if (IS_ERR(tsc->base)) {
 			ret = PTR_ERR(tsc->base);
@@ -530,11 +539,13 @@ static int rcar_gen3_thermal_probe(struct platform_device *pdev)
 	if (!rcar_gen3_thermal_read_fuses(priv))
 		dev_info(dev, "No calibration values fused, fallback to driver values\n");
 
+	rcar_gen3_thermal_shared_coefs(priv);
+
 	for (i = 0; i < priv->num_tscs; i++) {
 		struct rcar_gen3_thermal_tsc *tsc = priv->tscs[i];
 
 		rcar_gen3_thermal_init(priv, tsc);
-		rcar_gen3_thermal_calc_coefs(priv, tsc, priv->info->ths_tj_1);
+		rcar_gen3_thermal_tsc_coefs(priv, tsc);
 
 		zone = devm_thermal_of_zone_register(dev, i, tsc, &priv->ops);
 		if (IS_ERR(zone)) {