Re: [PATCH RFC 5/6] riscv: dts: thead: Add PVT node

[Drew Fustini <drew@pdp7.com>]

On Sun, Jun 01, 2025 at 09:50:52AM +0200, Michal Wilczynski wrote:
> 
> 
> On 5/27/25 10:00, Drew Fustini wrote:
> > On Sat, May 24, 2025 at 11:14:59PM +0200, Michal Wilczynski wrote:
> >> Add PVT DT node for thermal sensor.
> >>
> >> Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.com>
> >> ---
> >>  arch/riscv/boot/dts/thead/th1520.dtsi | 11 +++++++++++
> >>  1 file changed, 11 insertions(+)
> >>
> >> diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi b/arch/riscv/boot/dts/thead/th1520.dtsi
> >> index f24e12d7259fabcfbdc2dfa966d759db06684ab4..faf5c3aaf209b24cd99ddc377a88e08a8cce24fe 100644
> >> --- a/arch/riscv/boot/dts/thead/th1520.dtsi
> >> +++ b/arch/riscv/boot/dts/thead/th1520.dtsi
> >> @@ -648,6 +648,17 @@ padctrl_aosys: pinctrl@fffff4a000 {
> >>  			thead,pad-group = <1>;
> >>  		};
> >>  
> >> +		pvt: pvt@fffff4e000 {
> >> +			compatible = "moortec,mr75203";
> >> +			reg = <0xff 0xfff4e000 0x0 0x80>,
> >> +			      <0xff 0xfff4e080 0x0 0x100>,
> >> +			      <0xff 0xfff4e180 0x0 0x680>,
> >> +			      <0xff 0xfff4e800 0x0 0x600>;
> >> +			reg-names = "common", "ts", "pd", "vm";
> >> +			clocks = <&aonsys_clk>;
> >> +			#thermal-sensor-cells = <1>;
> >> +		};
> >> +
> >>  		gpio@fffff52000 {
> >>  			compatible = "snps,dw-apb-gpio";
> >>  			reg = <0xff 0xfff52000 0x0 0x1000>;
> >>
> >> -- 
> >> 2.34.1
> >>
> > 
> > I found that on my lpi4a that boot while hang after applying this patch.
> > I think that it is related to clocks as boot finished okay when using
> > clk_ignore_unused on the kernel cmdline. Do you happen have that in your
> > kernel cmdline?
> > 
> > I need to investigate further to understand which clocks are causing the
> > problem.
> > 
> > Thanks,
> > Drew
> > 
> 
> Thanks for your earlier message. I've investigated, and you were right
> about the clocks – the specific one causing the hang is CLK_CPU2AON_X2H.

Thanks for tracking down the clk causing the hang. I can confirm that
this fixes the boot hang:

diff --git a/drivers/clk/thead/clk-th1520-ap.c b/drivers/clk/thead/clk-th1520-ap.c
index ebfb1d59401d..4d0179b8c17c 100644
--- a/drivers/clk/thead/clk-th1520-ap.c
+++ b/drivers/clk/thead/clk-th1520-ap.c
@@ -792,7 +792,7 @@ static CCU_GATE(CLK_AON2CPU_A2X, aon2cpu_a2x_clk, "aon2cpu-a2x", axi4_cpusys2_ac
                0x134, BIT(8), 0);
 static CCU_GATE(CLK_X2X_CPUSYS, x2x_cpusys_clk, "x2x-cpusys", axi4_cpusys2_aclk_pd,
                0x134, BIT(7), 0);
-static CCU_GATE(CLK_CPU2AON_X2H, cpu2aon_x2h_clk, "cpu2aon-x2h", axi_aclk_pd, 0x138, BIT(8), 0);
+static CCU_GATE(CLK_CPU2AON_X2H, cpu2aon_x2h_clk, "cpu2aon-x2h", axi_aclk_pd, 0x138, BIT(8), CLK_IGNORE_UNUSED);
 static CCU_GATE(CLK_CPU2PERI_X2H, cpu2peri_x2h_clk, "cpu2peri-x2h", axi4_cpusys2_aclk_pd,
                0x140, BIT(9), CLK_IGNORE_UNUSED);
 static CCU_GATE(CLK_PERISYS_APB1_HCLK, perisys_apb1_hclk, "perisys-apb1-hclk", perisys_ahb_hclk_pd,

> 
> This appears to be an AHB bus clock required for CPU access to the AON
> domain. My proposed solution is to make the pvt node a child of a new
> parent bus node in the Device Tree. This new "AON bus" node would then
> explicitly request and manage CLK_CPU2AON_X2H, ensuring it's enabled
> when its children are accessed.
> 
> What are your thoughts on this approach?

I think that is a good approach. The alternative would be to just add
CLK_IGNORE_UNUSED like above. I've done it before but it is a bit of a
hack.

Thanks,
Drew