On Tue, Nov 19, 2019 at 12:03:31PM +0000, Andre Przywara wrote: > 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. > > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx> > > [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 Acked-by: Liviu Dudau <liviu.dudau@xxxxxxx> Best regards, Liviu > --- > arch/arm64/boot/dts/arm/juno-clocks.dtsi | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > 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"; > }; > > -- > 2.17.1 > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯
