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When SPI transfer is being prepared, the spi-s3c64xx driver will call
clk_set_rate() to change the rate of SPI source clock (IPCLK). But IPCLK
is a gate (leaf) clock, so it must propagate the rate change up the
clock tree, so that corresponding MUX/DIV clocks can actually change
their values. Add CLK_SET_RATE_PARENT flag to corresponding clocks for
all USI instances in GS101 PERIC1: USI{0, 9, 10, 11, 12, 13}. This change
involves the following clocks:

PERIC1 USI*:

    Clock                              Div range    MUX Selection
    -------------------------------------------------------------------
    gout_peric1_peric1_top0_ipclk_*    -            -
    dout_peric1_usi*_usi               /1..16       -
    mout_peric1_usi*_usi_user          -            {24.5 MHz, 400 MHz}

With input clock of 400 MHz this scheme provides the following IPCLK
rate range, for each USI block:

    PERIC1 USI*:       1.5 MHz ... 400 MHz

Accounting for internal /4 divider in SPI blocks, and because the max
SPI frequency is limited at 50 MHz, it gives us next SPI SCK rates:

    PERIC1 USI_SPI*:   384 KHz ... 49.9 MHz

Which shall be fine for the applications of the SPI bus.

Note that with this we allow the reparenting of the MUX_USIx clocks to
OSCCLK. Each instance of the USI IP has its own MUX_USI clock, thus the
reparenting of a MUX_USI clock corresponds to a single instance of the
USI IP. The datasheet mentions OSCCLK just in the low-power mode
context, but the downstream driver reparents too the MUX_USI clocks to
OSCCLK. Follow the downstream driver and do the same.

Fixes: 2999e786

 ("clk: samsung: gs101: add support for cmu_peric1")
Reviewed-by: Peter Griffin <peter.griffin@linaro.org>
Acked-by: André Draszik <andre.draszik@linaro.org>
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://lore.kernel.org/r/20240419100915.2168573-3-tudor.ambarus@linaro.org

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>