| From 115b91cb57bee7039d5926ccd8300a1430b3be52 Mon Sep 17 00:00:00 2001 |
| From: Andre Przywara <andre.przywara@arm.com> |
| Date: Tue, 19 Nov 2019 12:03:31 +0000 |
| Subject: [PATCH] arm64: dts: juno: Fix UART frequency |
| |
| commit 39a1a8941b27c37f79508426e27a2ec29829d66c upstream. |
| |
| Older versions of the Juno *SoC* TRM [1] recommended that the UART clock |
| source should be 7.2738 MHz, whereas the *system* TRM [2] stated a more |
| correct value of 7.3728 MHz. Somehow the wrong value managed to end up in |
| our DT. |
| |
| Doing a prime factorisation, a modulo divide by 115200 and trying |
| to buy a 7.2738 MHz crystal at your favourite electronics dealer suggest |
| that the old value was actually a typo. The actual UART clock is driven |
| by a PLL, configured via a parameter in some board.txt file in the |
| firmware, which reads 7.37 MHz (sic!). |
| |
| Fix this to correct the baud rate divisor calculation on the Juno board. |
| |
| [1] http://infocenter.arm.com/help/topic/com.arm.doc.ddi0515b.b/DDI0515B_b_juno_arm_development_platform_soc_trm.pdf |
| [2] http://infocenter.arm.com/help/topic/com.arm.doc.100113_0000_07_en/arm_versatile_express_juno_development_platform_(v2m_juno)_technical_reference_manual_100113_0000_07_en.pdf |
| |
| Fixes: 71f867ec130e ("arm64: Add Juno board device tree.") |
| Signed-off-by: Andre Przywara <andre.przywara@arm.com> |
| Acked-by: Liviu Dudau <liviu.dudau@arm.com> |
| Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/arch/arm64/boot/dts/arm/juno-clocks.dtsi b/arch/arm64/boot/dts/arm/juno-clocks.dtsi |
| index e5e265dfa902..2870b5eeb198 100644 |
| --- a/arch/arm64/boot/dts/arm/juno-clocks.dtsi |
| +++ b/arch/arm64/boot/dts/arm/juno-clocks.dtsi |
| @@ -8,10 +8,10 @@ |
| */ |
| / { |
| /* SoC fixed clocks */ |
| - soc_uartclk: refclk7273800hz { |
| + soc_uartclk: refclk7372800hz { |
| compatible = "fixed-clock"; |
| #clock-cells = <0>; |
| - clock-frequency = <7273800>; |
| + clock-frequency = <7372800>; |
| clock-output-names = "juno:uartclk"; |
| }; |
| |
| -- |
| 2.7.4 |
| |
