HI All,
I have further investigated this issue, please find my findings below
The "cpg_z_clk_round_rate" function is called 2 times from "dev_pm_opp_set_rate" (1 is direct call and other through "clk_set_rate") function.
For 500000000 frequency, after doing math operation(mult = div_u64(rate * 32ULL, prate);), it gets a factor 10--> 10.66 truncated to 10 and the frequency returned by the system is 468748125
On the second " cpg_z_clk_round_rate ", the below function make the value to worse, it gets a value of 9.9999, since it is integer division it is truncated to 9.
mult = div_u64(rate * 32ULL, prate);
Now the frequency 468748125, after doing math operation becomes 421874 KHz. This is the problem.
So I think the div_64 is wrong here, Instead we could go with DIV64_U64_ROUND_CLOSEST.
With "DIV64_U64_ROUND_CLOSEST" the factor is 10.66 which is rounded to 11.
So for 500000, after math operation, it becomes 515624
Please share your opinion this issue.
Regards,
Biju
> -----Original Message-----
> From: Biju Das
> Sent: Thursday, September 19, 2019 11:49 AM
> To: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>; Simon Horman
> <horms@xxxxxxxxxxxx>; linux-renesas-soc@xxxxxxxxxxxxxxx; Dien Pham
> <dien.pham.ry@xxxxxxxxxxxxxxx>; TAKESHI KIHARA
> <takeshi.kihara.df@xxxxxxxxxxx>; Niklas Söderlund
> <niklas.soderlund+renesas@xxxxxxxxxxxx>
> Subject: Regarding CPU frequency reported by Salvator-X board
>
> Hi All,
>
> I started testing frequency mentioned in OPP table with M3-W1.1 Salvator-X
> board (NOT salvator-XS) using user space governor
>
> The actual frequency reported for 0.5GHz(500000 KHz) is too much deviated
> from the target frequency [INFO] Target frequency: 500000 KHz [INFO]
> Actual frequency: 421874 KHz
>
> But if I change the extal value, as per the board schematic (16.6666MHz), the
> value is some what closer to target frequency.
> &extal_clk {
> - clock-frequency = <16666666>;
> + clock-frequency = <16666600>;
> };
> [INFO] Target frequency: 500000 KHz
> [INFO] Actual frequency: 468748 KHz
>
> Q1) Have any one seen this issue? Please share your thoughts on this issue.
>
> Note:-
> I am not seeing this issue on Salvator-XS board, where the extal_clk value=
> 16640000(16.64MHz).
>
> Please see the logs
> with clock-frequency = <16666666>;
> -----------------------------------------------
> root@salvator-x:/cip-test-scripts# ./opp_t_001.sh [INFO] Testing cpufreq for
> policy:
> [INFO] /sys/devices/system/cpu/cpufreq/policy0
> [INFO]
> [INFO] CPUs affected:
> [INFO] 0 1
> [INFO]
> [INFO] Available frequencies:
> [INFO] 500000 1000000 1500000
> [INFO]
> [INFO] Target frequency: 500000 KHz
> [INFO] Actual frequency: 421874 KHz
> [INFO]
> [INFO] Target frequency: 1000000 KHz
> [INFO] Actual frequency: 937499 KHz
> [INFO]
> [INFO] Target frequency: 1500000 KHz
> [INFO] Actual frequency: 1499999 KHz
> [INFO]
> [INFO] Testing cpufreq for policy:
> [INFO] /sys/devices/system/cpu/cpufreq/policy2
> [INFO]
> [INFO] CPUs affected:
> [INFO] 2 3 4 5
> [INFO]
> [INFO] Available frequencies:
> [INFO] 800000 1000000 1200000
> [INFO]
> [INFO] Target frequency: 800000 KHz
> [INFO] Actual frequency: 749999 KHz
> [INFO]
> [INFO] Target frequency: 1000000 KHz
> [INFO] Actual frequency: 974999 KHz
> [INFO]
> [INFO] Target frequency: 1200000 KHz
> [INFO] Actual frequency: 1199999 KHz
>
> With clock-frequency = <16666600>
> ----------------------------------------------
> root@salvator-x:/cip-test-scripts# ./opp_t_001.sh [INFO] Testing cpufreq for
> policy:
> [INFO] /sys/devices/system/cpu/cpufreq/policy0
> [INFO]
> [INFO] CPUs affected:
> [INFO] 0 1
> [INFO]
> [INFO] Available frequencies:
> [INFO] 500000 1000000 1500000
> [INFO]
> [INFO] Target frequency: 500000 KHz
> [INFO] Actual frequency: 468748 KHz
> [INFO]
> [INFO] Target frequency: 1000000 KHz
> [INFO] Actual frequency: 937496 KHz
> [INFO]
> [INFO] Target frequency: 1500000 KHz
> [INFO] Actual frequency: 1499994 KHz
> [INFO]
> [INFO] Testing cpufreq for policy:
> [INFO] /sys/devices/system/cpu/cpufreq/policy2
> [INFO]
> [INFO] CPUs affected:
> [INFO] 2 3 4 5
> [INFO]
> [INFO] Available frequencies:
> [INFO] 800000 1000000 1200000
> [INFO]
> [INFO] Target frequency: 800000 KHz
> [INFO] Actual frequency: 787496 KHz
> [INFO]
> [INFO] Target frequency: 1000000 KHz
> [INFO] Actual frequency: 974996 KHz
> [INFO]
> [INFO] Target frequency: 1200000 KHz
> [INFO] Actual frequency: 1199995 KHz
>
> Regards,
> Biju
>
