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clk_hw_round_rate() may call round rate function of its parents. In case of SAM9X60 two of USB parrents are PLLA and UPLL. These clocks are controlled by clk-sam9x60-pll.c driver. The round rate function for this driver is sam9x60_pll_round_rate() which call in turn sam9x60_pll_get_best_div_mul(). In case the requested rate is not in the proper range (rate < characteristics->output[0].min && rate > characteristics->output[0].max) the sam9x60_pll_round_rate() will return a negative number to its caller (called by clk_core_round_rate_nolock()). clk_hw_round_rate() will return zero in case a negative number is returned by clk_core_round_rate_nolock(). With this, the USB clock will continue its rate computation even caller of clk_hw_round_rate() returned an error. With this, the USB clock on SAM9X60 may not chose the best parent. I detected this after a suspend/resume cycle on SAM9X60. Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com> Link: https://lkml.kernel.org/r/1579261009-4573-2-git-send-email-claudiu.beznea@microchip.com Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.