net: stmmac: dwmac-qcom-ethqos: Use max frequency for clk_ptp_ref

Qualcomm clocks can set their frequency to a variety of levels
generally. Let's use the max for clk_ptp_ref to ensure the best
timestamping resolution possible.

Without this, the default value of the clock is used. For sa8775p-ride
this is 19.2 MHz, far less than the 230.4 MHz possible.
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Link: https://lore.kernel.org/r/20230725211853.895832-4-ahalaney@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c

@@ -694,6 +694,23 @@ static void ethqos_clks_disable(void *data)
 	ethqos_clks_config(data, false);
 }
 
+static void ethqos_ptp_clk_freq_config(struct stmmac_priv *priv)
+{
+	struct plat_stmmacenet_data *plat_dat = priv->plat;
+	int err;
+
+	if (!plat_dat->clk_ptp_ref)
+		return;
+
+	/* Max the PTP ref clock out to get the best resolution possible */
+	err = clk_set_rate(plat_dat->clk_ptp_ref, ULONG_MAX);
+	if (err)
+		netdev_err(priv->dev, "Failed to max out clk_ptp_ref: %d\n", err);
+	plat_dat->clk_ptp_rate = clk_get_rate(plat_dat->clk_ptp_ref);
+
+	netdev_dbg(priv->dev, "PTP rate %d\n", plat_dat->clk_ptp_rate);
+}
+
 static int qcom_ethqos_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
@@ -779,6 +796,7 @@ static int qcom_ethqos_probe(struct platform_device *pdev)
 	plat_dat->bsp_priv = ethqos;
 	plat_dat->fix_mac_speed = ethqos_fix_mac_speed;
 	plat_dat->dump_debug_regs = rgmii_dump;
+	plat_dat->ptp_clk_freq_config = ethqos_ptp_clk_freq_config;
 	plat_dat->has_gmac4 = 1;
 	if (ethqos->has_emac_ge_3)
 		plat_dat->dwmac4_addrs = &data->dwmac4_addrs;