[PATCH v2] arm64: dts: imx8mp: use correct clock for eqos timestamping counter

[PATCH v2] arm64: dts: imx8mp: use correct clock for eqos timestamping counter

[Johannes Zink]

The i.MX8MP Reference Manual rev 1 06/2021, section 11.7.2.5 "Timestamp
Support" indicates the PTP timestamp clock expects a typical frequency
of 125MHz.

As this also improves the precision of the measured timestamps: assign
appropriate 125MHz Clock parent. As no one except the timestamping
counter uses this clock, there are no side-effects of this change in
other peripherals.

Signed-off-by: Johannes Zink <j.zink@pengutronix.de>
---
Changes in v2:
- not only set assigned-clock-parents but alkso assigned-clock-rates for
  IMX8MP_CLK_ENET_QOS_TIMER to 125MHz (found by Fabio's review -
  thanks!)
- Link to v1: https://lore.kernel.org/r/20230719-imx8mp_enet_qos_use_125mhz_clock-v1-1-782c9ac6e121@pengutronix.de
---
Changes:
  v1 -> v2: Worked in Fabio's Feedback - Thank you for your review!
             - not only set assigned clock parent to 125MHz but also
	       set the assigned clock rate of IMX8MP_CLK_ENET_QOS_TIMER
	       to 125MHz
---
 arch/arm64/boot/dts/freescale/imx8mp.dtsi | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/boot/dts/freescale/imx8mp.dtsi b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
index 6f2f50e1639c..84ecf07affb3 100644
--- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
@@ -1334,9 +1334,9 @@ eqos: ethernet@30bf0000 {
 						  <&clk IMX8MP_CLK_ENET_QOS_TIMER>,
 						  <&clk IMX8MP_CLK_ENET_QOS>;
 				assigned-clock-parents = <&clk IMX8MP_SYS_PLL1_266M>,
-							 <&clk IMX8MP_SYS_PLL2_100M>,
+							 <&clk IMX8MP_SYS_PLL2_125M>,
 							 <&clk IMX8MP_SYS_PLL2_125M>;
-				assigned-clock-rates = <0>, <100000000>, <125000000>;
+				assigned-clock-rates = <0>, <125000000>, <125000000>;
 				nvmem-cells = <&eth_mac2>;
 				nvmem-cell-names = "mac-address";
 				intf_mode = <&gpr 0x4>;

---
base-commit: ba345b77fae7054d0cbd033283c47033e45db6d8
change-id: 20230719-imx8mp_enet_qos_use_125mhz_clock-1c4611c979ba

Best regards,
-- 
Johannes Zink <j.zink@pengutronix.de>


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Re: [PATCH v2] arm64: dts: imx8mp: use correct clock for eqos timestamping counter

[Fabio Estevam]

On Fri, Jul 21, 2023 at 12:51 AM Johannes Zink <j.zink@pengutronix.de> wrote:
>
> The i.MX8MP Reference Manual rev 1 06/2021, section 11.7.2.5 "Timestamp
> Support" indicates the PTP timestamp clock expects a typical frequency
> of 125MHz.
>
> As this also improves the precision of the measured timestamps: assign
> appropriate 125MHz Clock parent. As no one except the timestamping
> counter uses this clock, there are no side-effects of this change in
> other peripherals.
>
> Signed-off-by: Johannes Zink <j.zink@pengutronix.de>

Reviewed-by: Fabio Estevam <festevam@gmail.com>

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