8b03376580
commit c5c2a97b3ac7d1ec19e7cff9e38caca6afefc3de upstream.
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: 6a0712f6f199 ("PM / OPP: Add dev_pm_opp_set_rate()")
Cc: 4.6+ <stable@vger.kernel.org> # v4.6+
Signed-off-by: Waldemar Rymarkiewicz <waldemar.rymarkiewicz@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.