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This adds the NAND clocks (from the HHI_NAND_CLK_CNTL register) to the Meson8b clock driver. There are three NAND clocks: a gate which enables or disables the NAND clock, a mux and a divider (which divides the mux output). Unfortunately the public S805 datasheet does not document the mux parents. However, the vendor kernel has a few hints for us which allows us to make an educated guess about the clock parents. To do this we need to have a look at set_nand_core_clk() from the vendor's NAND driver (see [0]): - XTAL = (4<<9) | (1<<8) | 0 - 160MHz = (0<<9) | (1<<8) | 3) - 182MHz = (3<<9) | (1<<8) | 1) - 212MHz = (1<<9) | (1<<8) | 3) - 255MHz = (2<<9) | (1<<8) | 1) While there is a comment for the XTAL parent (which indicates that it should only be used for debugging) we have to do a bit of math for the other parents: target_freq * divider = rate of parent clock Bit 8 above is the enable bit, so we can ignore it here. Bits 11:9 are the mux index and bits 6:0 are the 0-based divider (so we need to add 1). This gives us: - mux 0 (160MHz * 4) = fclk_div4 (actual rate = 637.5MHz, off by 2.5MHz) - mux 1 (212MHz * 4) = fclk_div3 (actual rate = 850MHz, off by 2MHz) - mux 2 (255MHz * 2) = fclk_div5 (matches exactly 510MHz) - mux 3 (182MHz * 2) = fclk_div7 (actual rate = 346.3MHz, off by 0.3MHz) [0] https://github.com/khadas/linux/blob/9587681285cb/drivers/amlogic/amlnf/dev/amlnf_ctrl.c#L314 Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Linux kernel
============
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