Messages in this thread | | | Subject | Re: [PATCH] arm64: dts: rockchip: decrease rising edge time of UART2 | From | Katsuhiro Suzuki <> | Date | Sun, 3 Mar 2019 23:03:29 +0900 |
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Hello Heiko,
Thank you for comments.
On 2019/03/03 22:19, Heiko Stuebner wrote: > Hi, > > Am Sonntag, 3. März 2019, 13:27:05 CET schrieb Katsuhiro Suzuki: >> This patch increases drive strength of UART2 from 3mA to 12mA for >> getting more faster rising edge. >> >> RockPro64 is using a very high speed rate (1.5Mbps) for UART2. In >> this setting, a bit width of UART is about 667ns. >> >> In my environment (RockPro64 UART2 with FTDI FT232RL UART-USB >> converter), falling time of RockPro64 UART2 is 40ns, but riging time >> is over 650ns. So UART receiver will get wrong data, because receiver >> read intermediate data of rising edge. >> >> Rising time becomes 300ns from 650ns if apply this patch. This is not >> perfect solution but better than now. >> >> Signed-off-by: Katsuhiro Suzuki <katsuhiro@katsuster.net> >> --- >> arch/arm64/boot/dts/rockchip/rk3399.dtsi | 9 +++++++-- >> 1 file changed, 7 insertions(+), 2 deletions(-) > > your changing a core rk3399 property here, so I'd really like to get > input from other board stakeholders on this before applying a core > change. > > Could you either include the submitters of other rk3399-boards in the > recipient list so that they're aware or limit the change to rockpro64 for > the time being (aka overriding the property in the board-dts) please? >
OK, I'm adding other boards members. by ./scripts/get_maintainer.pl arch/arm64/boot/dts/rockchip/rk3399-*.dts
RockPro64 directly connect UART2 pins of RK3399 to external connector. I think maybe other RK3399 boards are facing same problem, but I cannot check it because I have RockPro64 only...
I'm happy if someone tell me other boards situation.
Best Regards, Katsuhiro Suzuki
> Thanks > Heiko > > > >> diff --git a/arch/arm64/boot/dts/rockchip/rk3399.dtsi b/arch/arm64/boot/dts/rockchip/rk3399.dtsi >> index beaa92744a64..e3c8f91ead50 100644 >> --- a/arch/arm64/boot/dts/rockchip/rk3399.dtsi >> +++ b/arch/arm64/boot/dts/rockchip/rk3399.dtsi >> @@ -2000,6 +2000,11 @@ >> drive-strength = <8>; >> }; >> >> + pcfg_pull_up_12ma: pcfg-pull-up-12ma { >> + bias-pull-up; >> + drive-strength = <12>; >> + }; >> + >> pcfg_pull_up_18ma: pcfg-pull-up-18ma { >> bias-pull-up; >> drive-strength = <18>; >> @@ -2521,8 +2526,8 @@ >> uart2c { >> uart2c_xfer: uart2c-xfer { >> rockchip,pins = >> - <4 RK_PC3 RK_FUNC_1 &pcfg_pull_up>, >> - <4 RK_PC4 RK_FUNC_1 &pcfg_pull_none>; >> + <4 RK_PC3 RK_FUNC_1 &pcfg_pull_up_12ma>, >> + <4 RK_PC4 RK_FUNC_1 &pcfg_pull_none_12ma>; >> }; >> }; >> >> > > > > > >
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