[PATCH] arm: dts: k3-am625-verdin-r5: Change CPU frequency to 1000MHz

[PATCH] arm: dts: k3-am625-verdin-r5: Change CPU frequency to 1000MHz

[Vitor Soares]

From: Vitor Soares <vitor.soares@toradex.com>

The same U-Boot binary is compatible with multiple Verdin AM62 board
variants. However, some of the SoC models can only operate at a maximum
speed of 1 GHz.

Previously, the boards with lower-speed grades were running at
overclocked speeds, leading to kernel complaints about unsupported
configurations.

To resolve this issue, the operating speed has been decreased to the
maximum allowable value across all Verdin AM62 board variants. As a
result, there is a regression in overall boot time, increasing by around
200 milliseconds for the faster SoC variant.

Signed-off-by: Vitor Soares <vitor.soares@toradex.com>
---
 arch/arm/dts/k3-am625-verdin-r5.dts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/dts/k3-am625-verdin-r5.dts b/arch/arm/dts/k3-am625-verdin-r5.dts
index 305d199678..6b03e7405a 100644
--- a/arch/arm/dts/k3-am625-verdin-r5.dts
+++ b/arch/arm/dts/k3-am625-verdin-r5.dts
@@ -23,7 +23,7 @@
 		 */
 		assigned-clocks = <&k3_clks 61 0>, <&k3_clks 135 0>, <&k3_clks 157 20>;
 		assigned-clock-parents = <&k3_clks 61 2>, <0>, <&k3_clks 157 22>;
-		assigned-clock-rates = <200000000>, <1200000000>, <25000000>;
+		assigned-clock-rates = <200000000>, <1000000000>, <25000000>;
 		clocks = <&k3_clks 61 0>;
 		power-domains = <&k3_pds 61 TI_SCI_PD_EXCLUSIVE>,
 				<&k3_pds 135 TI_SCI_PD_EXCLUSIVE>,
-- 
2.34.1

Re: [PATCH] arm: dts: k3-am625-verdin-r5: Change CPU frequency to 1000MHz

[Francesco Dolcini]

On Mon, Feb 19, 2024 at 12:34:08PM +0000, Vitor Soares wrote:
> From: Vitor Soares <vitor.soares@toradex.com>
> 
> The same U-Boot binary is compatible with multiple Verdin AM62 board
> variants. However, some of the SoC models can only operate at a maximum
> speed of 1 GHz.
> 
> Previously, the boards with lower-speed grades were running at
> overclocked speeds, leading to kernel complaints about unsupported
> configurations.
> 
> To resolve this issue, the operating speed has been decreased to the
> maximum allowable value across all Verdin AM62 board variants. As a
> result, there is a regression in overall boot time, increasing by around
> 200 milliseconds for the faster SoC variant.
> 
> Signed-off-by: Vitor Soares <vitor.soares@toradex.com>

Reviewed-by: Francesco Dolcini <francesco.dolcini@toradex.com>

Re: [PATCH] arm: dts: k3-am625-verdin-r5: Change CPU frequency to 1000MHz

[Vignesh Raghavendra]

On 19/02/24 18:04, Vitor Soares wrote:
> From: Vitor Soares <vitor.soares@toradex.com>
> 
> The same U-Boot binary is compatible with multiple Verdin AM62 board
> variants. However, some of the SoC models can only operate at a maximum
> speed of 1 GHz.
> 
> Previously, the boards with lower-speed grades were running at
> overclocked speeds, leading to kernel complaints about unsupported
> configurations.
> 
> To resolve this issue, the operating speed has been decreased to the
> maximum allowable value across all Verdin AM62 board variants. As a
> result, there is a regression in overall boot time, increasing by around
> 200 milliseconds for the faster SoC variant.
> 

Patch as such is fine. But one way to avoid boot regression is to fixup
the clock freq using based on speed grade identified by
k3_get_speed_grade() and freq mapping table for each letter as show in
datasheet [0]

This may need VDD_CORE voltage information via PMIC driver. Even w/o
that could at least bump to 1.25Ghz safely.

[0] https://www.ti.com/lit/ds/symlink/am625.pdf
Table 7-1. Device Speed Grades


> Signed-off-by: Vitor Soares <vitor.soares@toradex.com>
> ---
>  arch/arm/dts/k3-am625-verdin-r5.dts | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/dts/k3-am625-verdin-r5.dts b/arch/arm/dts/k3-am625-verdin-r5.dts
> index 305d199678..6b03e7405a 100644
> --- a/arch/arm/dts/k3-am625-verdin-r5.dts
> +++ b/arch/arm/dts/k3-am625-verdin-r5.dts
> @@ -23,7 +23,7 @@
>  		 */
>  		assigned-clocks = <&k3_clks 61 0>, <&k3_clks 135 0>, <&k3_clks 157 20>;
>  		assigned-clock-parents = <&k3_clks 61 2>, <0>, <&k3_clks 157 22>;
> -		assigned-clock-rates = <200000000>, <1200000000>, <25000000>;
> +		assigned-clock-rates = <200000000>, <1000000000>, <25000000>;
>  		clocks = <&k3_clks 61 0>;
>  		power-domains = <&k3_pds 61 TI_SCI_PD_EXCLUSIVE>,
>  				<&k3_pds 135 TI_SCI_PD_EXCLUSIVE>,

-- 
Regards
Vignesh

Re: [PATCH] arm: dts: k3-am625-verdin-r5: Change CPU frequency to 1000MHz

[Francesco Dolcini]

On Tue, Feb 20, 2024 at 10:47:03AM +0530, Vignesh Raghavendra wrote:
> 
> 
> On 19/02/24 18:04, Vitor Soares wrote:
> > From: Vitor Soares <vitor.soares@toradex.com>
> > 
> > The same U-Boot binary is compatible with multiple Verdin AM62 board
> > variants. However, some of the SoC models can only operate at a maximum
> > speed of 1 GHz.
> > 
> > Previously, the boards with lower-speed grades were running at
> > overclocked speeds, leading to kernel complaints about unsupported
> > configurations.
> > 
> > To resolve this issue, the operating speed has been decreased to the
> > maximum allowable value across all Verdin AM62 board variants. As a
> > result, there is a regression in overall boot time, increasing by around
> > 200 milliseconds for the faster SoC variant.
> > 
> 
> Patch as such is fine. But one way to avoid boot regression is to fixup
> the clock freq using based on speed grade identified by
> k3_get_speed_grade() and freq mapping table for each letter as show in
> datasheet [0]

Ack. I would still merge this as it is, I think that is conceptually
better to have a safe and valid value in the DT source file.

We can still do the optimization you suggested afterward, we just wanted
to get rid of any potential malfunction because of this overclocking as
soon as possible.

Francesco

Re: [PATCH] arm: dts: k3-am625-verdin-r5: Change CPU frequency to 1000MHz

[Tom Rini]

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On Mon, Feb 19, 2024 at 12:34:08PM +0000, Vitor Soares wrote:

> From: Vitor Soares <vitor.soares@toradex.com>
> 
> The same U-Boot binary is compatible with multiple Verdin AM62 board
> variants. However, some of the SoC models can only operate at a maximum
> speed of 1 GHz.
> 
> Previously, the boards with lower-speed grades were running at
> overclocked speeds, leading to kernel complaints about unsupported
> configurations.
> 
> To resolve this issue, the operating speed has been decreased to the
> maximum allowable value across all Verdin AM62 board variants. As a
> result, there is a regression in overall boot time, increasing by around
> 200 milliseconds for the faster SoC variant.
> 
> Signed-off-by: Vitor Soares <vitor.soares@toradex.com>
> Reviewed-by: Francesco Dolcini <francesco.dolcini@toradex.com>

Applied to u-boot/master, thanks!

-- 
Tom

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