Check for valid parameters in check rate. Else, we end up getting errors
like:
[ 0.000000] Division by zero in kernel.
[ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.17.0-rc1 #1
[ 0.000000] [<c0015160>] (unwind_backtrace) from [<c0011978>] (show_stack+0x10/0x14)
[ 0.000000] [<c0011978>] (show_stack) from [<c055f5f4>] (dump_stack+0x78/0x94)
[ 0.000000] [<c055f5f4>] (dump_stack) from [<c02e17cc>] (Ldiv0+0x8/0x10)
[ 0.000000] [<c02e17cc>] (Ldiv0) from [<c047d228>] (ti_clk_divider_set_rate+0x14/0x14c)
[ 0.000000] [<c047d228>] (ti_clk_divider_set_rate) from [<c047a938>] (clk_change_rate+0x138/0x180)
[ 0.000000] [<c047a938>] (clk_change_rate) from [<c047a908>] (clk_change_rate+0x108/0x180)
This occurs as part of the inital clock tree update of child clock nodes
where new_rate could be 0 for non functional clocks.
Fixes: b4761198bf ("CLK: ti: add support for ti divider-clock")
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
ti/clk-divider.c does not calculate the rates consistently at the moment.
As an example, on OMAP3 we have a clock divider with a source clock of
864000000 Hz. With dividers 6, 7 and 8 the theoretical rates are:
6: 144000000
7: 123428571.428571...
8: 108000000
Calling clk_round_rate() with the rate in the first column will give the
rate in the second column:
144000000 -> 144000000
143999999 -> 123428571
123428572 -> 123428571
123428571 -> 108000000
Note how clk_round_rate() returns 123428571 for rates from 123428572 to
143999999, which is mathematically correct, but when clk_round_rate() is
called with 123428571, the returned value is surprisingly 108000000.
This means that the following code works a bit oddly:
rate = clk_round_rate(clk, 123428572);
clk_set_rate(clk, rate);
As clk_set_rate() also does clock rate rounding, the result is that the
clock is set to the rate of 108000000, not 123428571 returned by the
clk_round_rate.
This patch changes the ti/clk-divider.c to use DIV_ROUND_UP when
calculating the rate. This gives the following behavior which fixes the
inconsistency:
144000000 -> 144000000
143999999 -> 123428572
123428572 -> 123428572
123428571 -> 108000000
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
This patch adds support for TI divider clock binding, which simply uses
the basic clock divider to provide the features needed.
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
