This PR improves the EMI performance of the TAC (at least when measuring the emissions on pins of the IOBus port in isolation).
How can that be you ask? The VCC_IO supply line powering all of the SoC's GPIO pins is necessarily affected by high frequency switching of e.g. the RGMII and eMMC lines. This results in GPIOs that are actively driven high also containing said noise.
This PR makes it so that the lines are never driven high by the SoC, relying instead on pull-up resistors on the power board.
Related Pull Requests
This PR is based on other PRs that should be merged first:
[ ] The meta-lxatac pull request that last touched the kernel patch stack: #52
[x] The tacd pull request that drives the GPIOs as open drain linux-automation/tacd#31
This PR improves the EMI performance of the TAC (at least when measuring the emissions on pins of the IOBus port in isolation).
How can that be you ask? The VCC_IO supply line powering all of the SoC's GPIO pins is necessarily affected by high frequency switching of e.g. the RGMII and eMMC lines. This results in GPIOs that are actively driven high also containing said noise. This PR makes it so that the lines are never driven high by the SoC, relying instead on pull-up resistors on the power board.
Related Pull Requests
This PR is based on other PRs that should be merged first:
meta-lxatacpull request that last touched the kernel patch stack: #52tacdpull request that drives the GPIOs as open drain linux-automation/tacd#31