• Maxime Ripard's avatar
    ASoC: tlv320aic32x4: Add a determine_rate hook · 218b95ba
    Maxime Ripard authored
    The tlv320aic32x4 clkin clock implements a mux with a set_parent hook,
    but doesn't provide a determine_rate implementation.
    
    This is a bit odd, since set_parent() is there to, as its name implies,
    change the parent of a clock. However, the most likely candidates to
    trigger that parent change are either the assigned-clock-parents device
    tree property or a call to clk_set_rate(), with determine_rate()
    figuring out which parent is the best suited for a given rate.
    
    The other trigger would be a call to clk_set_parent(), but it's far less
    used, and it doesn't look like there's any obvious user for that clock.
    
    Similarly, it doesn't look like the device tree using that clock driver
    uses any of the assigned-clock properties on that clock.
    
    So, the set_parent hook is effectively unused, possibly because of an
    oversight. However, it could also be an explicit decision by the
    original author to avoid any reparenting but through an explicit call to
    clk_set_parent().
    
    The latter case would be equivalent to setting the determine_rate
    implementation to clk_hw_determine_rate_no_reparent(). Indeed, if no
    determine_rate implementation is provided, clk_round_rate() (through
    clk_core_round_rate_nolock()) will call itself on the parent if
    CLK_SET_RATE_PARENT is set, and will not change the clock rate
    otherwise.
    
    And if it was an oversight, then we are at least explicit about our
    behavior now and it can be further refined down the line.
    
    Cc: Jaroslav Kysela <perex@perex.cz>
    Cc: Liam Girdwood <lgirdwood@gmail.com>
    Cc: Mark Brown <broonie@kernel.org>
    Cc: Takashi Iwai <tiwai@suse.com>
    Cc: alsa-devel@alsa-project.org
    Signed-off-by: default avatarMaxime Ripard <maxime@cerno.tech>
    Link: https://lore.kernel.org/r/20221018-clk-range-checks-fixes-v4-46-971d5077e7d2@cerno.techSigned-off-by: default avatarStephen Boyd <sboyd@kernel.org>
    218b95ba
tlv320aic32x4-clk.c 11.6 KB