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6dbcc962e4
Currently, Tegra peripheral drivers control two aspects of their HW module clock(s): 1) The clock enable/rate for the peripheral clock itself. 2) The system-level clock tree setup, i.e. the clock parent. Aspect 1 is reasonable, but aspect 2 is a system-level decision, not something that an individual peripheral driver should in general know about or influence. Such system-level knowledge ties the driver to a specific SoC implementation, even when they use generic APIs for clock manipulation, since they must have SoC-specific knowledge such as parent clock IDs. Limited exceptions exist, such as where peripheral HW is expected to dynamically switch between clock sources at run-time, such as CPU clock scaling or display clock conflict management in a multi-head scenario. This patch enhances the Tegra core code to perform system-level clock tree setup, in a similar fashion to the Linux kernel Tegra clock driver. This will allow future patches to simplify peripheral drivers by removing the clock parent setup logic. This change is required prior to converting peripheral drivers to use the standard clock APIs, since: 1) The clock uclass doesn't currently support a set_parent() operation. Adding one is possible, but not necessary at the moment. 2) The clock APIs retrieve all clock IDs from device tree, and the DT bindings for almost all peripherals only includes information about the relevant peripheral clocks, and not any potential parent clocks. Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Tom Warren <twarren@nvidia.com> |
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