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The DRAM controller clock is only allowed to change frequency while the DRAM chips are in self-refresh. To support this, changes to the CLK_DRAM mux and divider have no effect until acknowledged by the memory dynamic frequency scaling (MDFS) hardware inside the DRAM controller. (There is a SDRCLK_UPD bit in DRAM_CFG_REG which should serve a similar purpose, but this bit actually does nothing.) However, the MDFS hardware in H3 appears to be broken. Triggering a frequency change using the procedure from similar SoCs (A64/H5) hangs the hardware. Additionally, the vendor BSP specifically avoids using the MDFS hardware on H3, instead performing all DRAM PHY parameter updates and resets in software. Thus, it is effectively impossible to change the CLK_DRAM mux/divider, so those features should not be modeled. Add CLK_SET_RATE_PARENT so frequency changes apply to PLL_DDR instead. Signed-off-by: Samuel Holland <samuel@sholland.org> Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com> Link: https://lore.kernel.org/r/20221229042230.24532-1-samuel@sholland.org Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.