stmmac: ptp: fix the reference clock

The PTP reference clock, used for setting the addend in the Timestamp Addend
Register, was erroneously hard-coded (as reported in the databook just as
example).

The patch removes the macro named: STMMAC_SYSCLOCK and allows to use a
reference clock (clk_ptp_ref_i) that can be passed from the platform.

If not passed, the main driver clock will be used as default; note that
this can be fine on some platforms.

Note that, prior this patch, using the old STMMAC_SYSCLOCK on some platforms,
as side effect, the ptp clock can move faster/slower than the system clock.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 22 insertions, 6 deletions

diff --git a/Documentation/devicetree/bindings/net/stmmac.txt b/Documentation/devicetree/bindings/net/stmmac.txt
index 9b03c57563a4..e45ac3f926b1 100644
--- a/Documentation/devicetree/bindings/net/stmmac.txt
+++ b/Documentation/devicetree/bindings/net/stmmac.txt
@@ -39,6 +39,10 @@ Optional properties:
   further clocks may be specified in derived bindings.
 - clock-names: One name for each entry in the clocks property, the
   first one should be "stmmaceth".
+- clk_ptp_ref: this is the PTP reference clock; in case of the PTP is
+  available this clock is used for programming the Timestamp Addend Register.
+  If not passed then the system clock will be used and this is fine on some
+  platforms.
 
 Examples:
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index ca01035634a7..128a0b723a00 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -105,6 +105,8 @@ struct stmmac_priv {
         struct ptp_clock *ptp_clock;
         struct ptp_clock_info ptp_clock_ops;
         unsigned int default_addend;
+        struct clk *clk_ptp_ref;
+        unsigned int clk_ptp_rate;
         u32 adv_ts;
         int use_riwt;
         int irq_wake;
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 51a89d4bb125..03652891fcbf 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -603,16 +603,16 @@ static int stmmac_hwtstamp_ioctl(struct net_device *dev, struct ifreq *ifr)
                 /* calculate default added value:
                  * formula is :
                  * addend = (2^32)/freq_div_ratio;
-                 * where, freq_div_ratio = STMMAC_SYSCLOCK/50MHz
-                 * hence, addend = ((2^32) * 50MHz)/STMMAC_SYSCLOCK;
-                 * NOTE: STMMAC_SYSCLOCK should be >= 50MHz to
+                 * where, freq_div_ratio = clk_ptp_ref_i/50MHz
+                 * hence, addend = ((2^32) * 50MHz)/clk_ptp_ref_i;
+                 * NOTE: clk_ptp_ref_i should be >= 50MHz to
                  *       achive 20ns accuracy.
                  *
                  * 2^x * y == (y << x), hence
                  * 2^32 * 50000000 ==> (50000000 << 32)
                  */
                 temp = (u64) (50000000ULL << 32);
-                priv->default_addend = div_u64(temp, STMMAC_SYSCLOCK);
+                priv->default_addend = div_u64(temp, priv->clk_ptp_rate);
                 priv->hw->ptp->config_addend(priv->ioaddr,
                                              priv->default_addend);
 
@@ -638,6 +638,16 @@ static int stmmac_init_ptp(struct stmmac_priv *priv)
         if (!(priv->dma_cap.time_stamp || priv->dma_cap.atime_stamp))
                 return -EOPNOTSUPP;
 
+        /* Fall-back to main clock in case of no PTP ref is passed */
+        priv->clk_ptp_ref = devm_clk_get(priv->device, "clk_ptp_ref");
+        if (IS_ERR(priv->clk_ptp_ref)) {
+                priv->clk_ptp_rate = clk_get_rate(priv->stmmac_clk);
+                priv->clk_ptp_ref = NULL;
+        } else {
+                clk_prepare_enable(priv->clk_ptp_ref);
+                priv->clk_ptp_rate = clk_get_rate(priv->clk_ptp_ref);
+        }
+
         priv->adv_ts = 0;
         if (priv->dma_cap.atime_stamp && priv->extend_desc)
                 priv->adv_ts = 1;
@@ -657,6 +667,8 @@ static int stmmac_init_ptp(struct stmmac_priv *priv)
 
 static void stmmac_release_ptp(struct stmmac_priv *priv)
 {
+        if (priv->clk_ptp_ref)
+                clk_disable_unprepare(priv->clk_ptp_ref);
         stmmac_ptp_unregister(priv);
 }
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
index 3dbc047622fa..4535df37c227 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
@@ -25,8 +25,6 @@
 #ifndef __STMMAC_PTP_H__
 #define __STMMAC_PTP_H__
 
-#define STMMAC_SYSCLOCK 62500000
-
 /* IEEE 1588 PTP register offsets */
 #define PTP_TCR         0x0700  /* Timestamp Control Reg */
 #define PTP_SSIR        0x0704  /* Sub-Second Increment Reg */