• Waldemar Rymarkiewicz's avatar
    PM / OPP: Update voltage in case freq == old_freq · c5c2a97b
    Waldemar Rymarkiewicz authored
    This commit fixes a rare but possible case when the clk rate is updated
    without update of the regulator voltage.
    
    At boot up, CPUfreq checks if the system is running at the right freq. This
    is a sanity check in case a bootloader set clk rate that is outside of freq
    table present with cpufreq core. In such cases system can be unstable so
    better to change it to a freq that is preset in freq-table.
    
    The CPUfreq takes next freq that is >= policy->cur and this is our
    target_freq that needs to be set now.
    
    dev_pm_opp_set_rate(dev, target_freq) checks the target_freq and the
    old_freq (a current rate). If these are equal it returns early. If not,
    it searches for OPP (old_opp) that fits best to old_freq (not listed in
    the table) and updates old_freq (!).
    
    Here, we can end up with old_freq = old_opp.rate = target_freq, which
    is not handled in _generic_set_opp_regulator(). It's supposed to update
    voltage only when freq > old_freq  || freq > old_freq.
    
    if (freq > old_freq) {
    		ret = _set_opp_voltage(dev, reg, new_supply);
    [...]
    if (freq < old_freq) {
    		ret = _set_opp_voltage(dev, reg, new_supply);
    		if (ret)
    
    It results in, no voltage update while clk rate is updated.
    
    Example:
    freq-table = {
    	1000MHz   1.15V
    	 666MHZ   1.10V
    	 333MHz   1.05V
    }
    boot-up-freq        = 800MHz   # not listed in freq-table
    freq = target_freq  = 1GHz
    old_freq            = 800Mhz
    old_opp = _find_freq_ceil(opp_table, &old_freq);  #(old_freq is modified!)
    old_freq            = 1GHz
    
    Fixes: 6a0712f6 ("PM / OPP: Add dev_pm_opp_set_rate()")
    Cc: 4.6+ <stable@vger.kernel.org> # v4.6+
    Signed-off-by: default avatarWaldemar Rymarkiewicz <waldemar.rymarkiewicz@gmail.com>
    Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
    c5c2a97b
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