| Message ID | 20210825122757.91133-1-aford173@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: dts: renesas: beacon: Fix i2c2 speed calcuation | expand |
On Wed, Aug 25, 2021 at 02:47:21PM +0200, Geert Uytterhoeven wrote: > CC Wolfram > > On Wed, Aug 25, 2021 at 2:28 PM Adam Ford <aford173@gmail.com> wrote: > > The desired i2c2 speed is 400KHz, but when measured on a scope, it > > is incorrect. The driver can use the i2c-scl-rising-time-ns to help > > calculate the proper setting to get exactly 400KHz. The question for me is: Has it been measured that SCL rising time is really 50ns or has it been measured that the bus clock is now exactly 400kHz?
On Tue, Sep 14, 2021 at 5:41 AM Wolfram Sang <wsa+renesas@sang-engineering.com> wrote: > > On Wed, Aug 25, 2021 at 02:47:21PM +0200, Geert Uytterhoeven wrote: > > CC Wolfram > > > > On Wed, Aug 25, 2021 at 2:28 PM Adam Ford <aford173@gmail.com> wrote: > > > The desired i2c2 speed is 400KHz, but when measured on a scope, it > > > is incorrect. The driver can use the i2c-scl-rising-time-ns to help > > > calculate the proper setting to get exactly 400KHz. > > The question for me is: Has it been measured that SCL rising time is > really 50ns or has it been measured that the bus clock is now exactly > 400kHz? The person who originally reported this to me moved on, so I don't know if he measured both the rise time or just the clock speed. I know originally, the clock speed was measured to be 426KHz instead of 400KHz, and with the change to the rise time, the measured clock speed was exactly 400KHz. I do not know if the measured rise time is really 50ns or not. adam >
diff --git a/arch/arm64/boot/dts/renesas/beacon-renesom-baseboard.dtsi b/arch/arm64/boot/dts/renesas/beacon-renesom-baseboard.dtsi index 2692cc64bff6..987357c58390 100644 --- a/arch/arm64/boot/dts/renesas/beacon-renesom-baseboard.dtsi +++ b/arch/arm64/boot/dts/renesas/beacon-renesom-baseboard.dtsi @@ -328,6 +328,7 @@ &hsusb { &i2c2 { status = "okay"; clock-frequency = <400000>; + i2c-scl-rising-time-ns = <50>; pinctrl-0 = <&i2c2_pins>; pinctrl-names = "default";
The desired i2c2 speed is 400KHz, but when measured on a scope, it is incorrect. The driver can use the i2c-scl-rising-time-ns to help calculate the proper setting to get exactly 400KHz. Fixes: 900d9fc3bece ("arm64: dts: renesas: beacon: Correct I2C bus speeds") Signed-off-by: Adam Ford <aford173@gmail.com>