[PATCH v2 1/1] arm64: dts: ti: k3-j784s4-j742s2-evm-common: Set ACSPCIe refclk to MAIN_PLL2_HSDIV4 for pcie1

Commit e3dfcf482d07 ("arm64: dts: ti: k3-j784s4-j742s2-evm-common:
Enable ACSPCIE0 output for PCIe1") enabled the ACSPCIE0 buffers
to provide the PCIe refclk for PCIe1, but introduced a bug
where the clock is remporarily disabled during initialization.
The ACSPCIe reference clock is muxable between multiple
sources: SERDESx_REF_DER_OUT_CLK, MAIN_PLL2_HSDIV4_CLKOUT, and
SERDESx_REF_OUT_CLK [0]. On reset, the refclk is set to the
SERDESx_REF_DER_OUT_CLK. In the J742S2 and J784S4, "the SerDes PCIe
Reference Clock Output will be temporarily disabled when changing Data
Rates to or from 8.0 GT/s in Derived Refclk mode" [1]. Some external PCIe
devices cannot tolerate the reference clock being disabled and will
therefore fail to link.

This advisory is described in more detail as: i2242 of the J784S4
Silicon Revision 1.0 (Rev. B) document [1].

The refclk for devices connected to PCIe1 is provided by the ACSPCIe
buffers in the J742S2XH01EVM [2] and J784S4XEVM [3]. Work around
the advisory by setting the ACSPCIe reference clock source to
MAIN_PLL2_HSDIV4_CLKOUT. Use the TI SCI clock controller to assign the
clock's source [4].

[0] https://www.ti.com/lit/zip/spruj52
[1] https://www.ti.com/lit/pdf/SPRZ536
[2] https://www.ti.com/lit/zip/SPAC001
[3] https://www.ti.com/lit/zip/SPRR458
[4] https://software-dl.ti.com/tisci/esd/latest/5_soc_doc/j784s4/clocks.html

Fixes: e3dfcf482d07 ("arm64: dts: ti: k3-j784s4-j742s2-evm-common: Enable ACSPCIE0 output for PCIe1")
Reviewed-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Signed-off-by: Jared McArthur <redacted>
---
v2 changes:
- Added "Fixes" tag and edited the message to explain the fix
- Changed SPRZ536 link to immutable link
- Added Siddarth's reviewed-by

v1 link: https://lore.kernel.org/all/20260828195140.3476062-1-j-mcarthur@ti.com/ (local)

 arch/arm64/boot/dts/ti/k3-j784s4-j742s2-evm-common.dtsi | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-evm-common.dtsi b/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-evm-common.dtsi
index ff3a85cbc524a..7c085663c8880 100644
--- a/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-evm-common.dtsi
+++ b/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-evm-common.dtsi

@@ -1206,6 +1206,8 @@ &pcie1_rc {
 	status = "okay";
 	clocks = <&k3_clks 333 0>, <&serdes0 CDNS_TORRENT_REFCLK_DRIVER>;
 	clock-names = "fck", "pcie_refclk";
+	assigned-clocks = <&k3_clks 415 0>;
+	assigned-clock-parents = <&k3_clks 415 2>;
 	num-lanes = <2>;
 	reset-gpios = <&exp1 2 GPIO_ACTIVE_HIGH>;
 	phys = <&serdes0_pcie1_link>;

-- 
2.34.1