Improve reliability at higher bus speeds #6050
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popcornmix
approved these changes
Mar 18, 2024
This was referenced Mar 18, 2024
[1] calculates timings for arbitrary clock speeds, but it does so aiming for a 50% SCL duty cycle. This is the wrong goal, particularly for high clock speeds, because it doesn't allow the device sufficient time to pull the bus low to issue an ACK. Change the algorithm to aim for the minimum SCL high time (tHIGH) for the requested speed according to the I2C Specification, using linear interpolation between the values for the standard speeds. Signed-off-by: Phil Elwell <phil@raspberrypi.com> [1] commit cea76e5 ("i2c: designware: Support non-standard bus speeds")
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Mar 19, 2024
See: raspberrypi/linux#6054 kernel: overlays: i2c-rtc: pcf8563 supports wakeup-source See: raspberrypi/linux#6052 kernel: ARM: dts: bcm2712: Move /soc/sound to bcm2712-rpi See: raspberrypi/linux#6051 kernel: I2C: Improve reliability at higher bus speeds See: raspberrypi/linux#6050 kernel: dmaengine: dw-axi-dmac: Fix a non-atomic update See: raspberrypi/linux#6044 kernel: dtoverlays: Add a disconnect_on_idle override to i2c-mux See: raspberrypi/linux#6040 kernel: Add support for generic i2c-mux base-nr property See: raspberrypi/linux#6038 kernel: dtoverlays: Fixup pendown gpio polarity for ads7846 users See: raspberrypi/linux#6029
popcornmix
added a commit
to raspberrypi/rpi-firmware
that referenced
this pull request
Mar 19, 2024
See: raspberrypi/linux#6054 kernel: overlays: i2c-rtc: pcf8563 supports wakeup-source See: raspberrypi/linux#6052 kernel: ARM: dts: bcm2712: Move /soc/sound to bcm2712-rpi See: raspberrypi/linux#6051 kernel: I2C: Improve reliability at higher bus speeds See: raspberrypi/linux#6050 kernel: dmaengine: dw-axi-dmac: Fix a non-atomic update See: raspberrypi/linux#6044 kernel: dtoverlays: Add a disconnect_on_idle override to i2c-mux See: raspberrypi/linux#6040 kernel: Add support for generic i2c-mux base-nr property See: raspberrypi/linux#6038 kernel: dtoverlays: Fixup pendown gpio polarity for ads7846 users See: raspberrypi/linux#6029
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cea76e5 calculates timings for arbitrary clock speeds, but it does so aiming for a 50% SCL duty cycle. This is the wrong goal, particularly for high clock speeds, but it doesn't allow the device sufficient time to pull the bus low to issue an ACK.
Change the algorithm to aim for the minimum SCL high time (tHIGH) for the requested speed according to the I2C Specification, using linear interpolation between the values for the standard speeds.