* J.D. Schroeder <Linux.HWI@xxxxxxxxxx> [160503 06:32]: > On 05/03/2016 03:16 AM, Tero Kristo wrote: > > On 02/05/16 20:12, J.D. Schroeder wrote: > >> From: "J.D. Schroeder" <jay.schroeder@xxxxxxxxxx> > >> > >> This commit updates the OSC_32K_CLK (secure_32k_clk_src_ck) frequency > >> from the precise 32kHz frequency (i.e., 32.768 kHz) to a more > >> accurate frequency of ~34.6 kHz. Actual measured frequencies of the > >> clock vary from processor to processor anywhere from 34.4 kHz up to > >> 34.8 kHz. Note that the ~34 kHz frequency clock is generated > >> internally by the processor, not an input to the processor. This > >> change makes it more clear that the consumer of the > >> secure_32k_clk_src_ck will not get a precise 32.768 kHz frequency > >> output. > >> > >> Signed-off-by: J.D. Schroeder <jay.schroeder@xxxxxxxxxx> > >> Reviewed-by: Trenton Andres <trenton.andres@xxxxxxxxxx> > >> --- > >> arch/arm/boot/dts/dra7xx-clocks.dtsi | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/arch/arm/boot/dts/dra7xx-clocks.dtsi > >> b/arch/arm/boot/dts/dra7xx-clocks.dtsi > >> index 3f0c61d..f7ec976 100644 > >> --- a/arch/arm/boot/dts/dra7xx-clocks.dtsi > >> +++ b/arch/arm/boot/dts/dra7xx-clocks.dtsi > >> @@ -95,7 +95,7 @@ > >> secure_32k_clk_src_ck: secure_32k_clk_src_ck { > >> #clock-cells = <0>; > >> compatible = "fixed-clock"; > >> - clock-frequency = <32768>; > >> + clock-frequency = <34600>; /* approximate frequency */ > >> }; > >> > >> sys_clk32_crystal_ck: sys_clk32_crystal_ck { > >> > > > > I still don't agree with this patch. The actual frequency can drift much more, > > you are just seeing this number at your setup. > > Yes, it can drift significantly from processor to processor. Do you agree that > this frequency is closer to what can be expected than 32768 Hz? > > Like I said, I would have renamed the clock also but I opted to go the less > obtrusive route while still helping others that might think they can > reasonably use this clock in their design as a 32768 Hz clock source. Perhaps > my comment and selection of the approximate frequency is not the best (I'm > open for suggestions). However, I do think this change is an improvement and > clarifying change to what is currently present in the clock description. Does a fixed divider calculation of input * (32768 / 0x27e6) make sense here too as pointed out earlier by Matthijs for the ti81xx? Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html