net: ethernet: renesas: rcar_gen4_ptp: Get clock increment from clock rate

Instead of using hard coded clock increment values for each SoC derive
the clock increment from the module clock. This is done in preparation
to support a second platform, R-Car V4H that uses a 200Mhz clock
compared with the 320Mhz clock used on R-Car S4.

Tested on both SoCs,

S4 reports a clock of 320000000Hz which gives a value of 0x19000000.
Documentation says a 320Mhz clock is used and the correct increment for
that clock is 0x19000000.

V4H reports a clock of 199999992Hz which gives a value of 0x2800001a.
Documentation says a 200Mhz clock is used and the correct increment for
that clock is 0x28000000.
Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/renesas/rcar_gen4_ptp.c

@@ -141,8 +141,18 @@ static int rcar_gen4_ptp_set_offs(struct rcar_gen4_ptp_private *ptp_priv,
 	return 0;
 }
 
+static s64 rcar_gen4_ptp_rate_to_increment(u32 rate)
+{
+	/* Timer increment in ns.
+	 * bit[31:27] - integer
+	 * bit[26:0]  - decimal
+	 * increment[ns] = perid[ns] * 2^27 => (1ns * 2^27) / rate[hz]
+	 */
+	return div_s64(1000000000LL << 27, rate);
+}
+
 int rcar_gen4_ptp_register(struct rcar_gen4_ptp_private *ptp_priv,
-			   enum rcar_gen4_ptp_reg_layout layout, u32 clock)
+			   enum rcar_gen4_ptp_reg_layout layout, u32 rate)
 {
 	int ret;
 
@@ -155,7 +165,7 @@ int rcar_gen4_ptp_register(struct rcar_gen4_ptp_private *ptp_priv,
 	if (ret)
 		return ret;
 
-	ptp_priv->default_addend = clock;
+	ptp_priv->default_addend = rcar_gen4_ptp_rate_to_increment(rate);
 	iowrite32(ptp_priv->default_addend, ptp_priv->addr + ptp_priv->offs->increment);
 	ptp_priv->clock = ptp_clock_register(&ptp_priv->info, NULL);
 	if (IS_ERR(ptp_priv->clock))

drivers/net/ethernet/renesas/rcar_gen4_ptp.h

@@ -9,8 +9,6 @@
 
 #include <linux/ptp_clock_kernel.h>
 
-#define PTPTIVC_INIT			0x19000000	/* 320MHz */
-#define RCAR_GEN4_PTP_CLOCK_S4		PTPTIVC_INIT
 #define RCAR_GEN4_GPTP_OFFSET_S4	0x00018000
 
 enum rcar_gen4_ptp_reg_layout {
@@ -64,7 +62,7 @@ struct rcar_gen4_ptp_private {
 };
 
 int rcar_gen4_ptp_register(struct rcar_gen4_ptp_private *ptp_priv,
-			   enum rcar_gen4_ptp_reg_layout layout, u32 clock);
+			   enum rcar_gen4_ptp_reg_layout layout, u32 rate);
 int rcar_gen4_ptp_unregister(struct rcar_gen4_ptp_private *ptp_priv);
 struct rcar_gen4_ptp_private *rcar_gen4_ptp_alloc(struct platform_device *pdev);
 

drivers/net/ethernet/renesas/rswitch.c

@@ -1829,7 +1829,7 @@ static int rswitch_init(struct rswitch_private *priv)
 	rswitch_fwd_init(priv);
 
 	err = rcar_gen4_ptp_register(priv->ptp_priv, RCAR_GEN4_PTP_REG_LAYOUT,
-				     RCAR_GEN4_PTP_CLOCK_S4);
+				     clk_get_rate(priv->clk));
 	if (err < 0)
 		goto err_ptp_register;