[net-next v3 4/5] net: ethernet: renesas: rcar_gen4_ptp: Get clock increment from clock rate

[Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>]

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@xxxxxxxxxxxxxx>
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
---
* Changes since v2
- No change.

* Changes since v1
- New in v2. In v1 a patch adding a new hard coded value for V4H was
  present, that patch have been dropped in favor of this approach.
---
 drivers/net/ethernet/renesas/rcar_gen4_ptp.c | 14 ++++++++++++--
 drivers/net/ethernet/renesas/rcar_gen4_ptp.h |  4 +---
 drivers/net/ethernet/renesas/rswitch.c       |  2 +-
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/renesas/rcar_gen4_ptp.c b/drivers/net/ethernet/renesas/rcar_gen4_ptp.c
index 59f6351e9ae9..9583894634ae 100644
--- a/drivers/net/ethernet/renesas/rcar_gen4_ptp.c
+++ b/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))
diff --git a/drivers/net/ethernet/renesas/rcar_gen4_ptp.h b/drivers/net/ethernet/renesas/rcar_gen4_ptp.h
index 35664d1dc472..e22da5acd53d 100644
--- a/drivers/net/ethernet/renesas/rcar_gen4_ptp.h
+++ b/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);
 
diff --git a/drivers/net/ethernet/renesas/rswitch.c b/drivers/net/ethernet/renesas/rswitch.c
index e1e29a2caf22..d6089429f654 100644
--- a/drivers/net/ethernet/renesas/rswitch.c
+++ b/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;
 
-- 
2.42.1