| Message ID | 20230212-clk-qcom-determine_rate-v1-0-b4e447d4926e@z3ntu.xyz (mailing list archive) |
|---|---|
| Headers | show |
| Series | Switch hfpll & krait clock drivers to .determine_rate | expand |
On Sun, 12 Feb 2023 15:11:07 +0100, Luca Weiss wrote: > While trying to get cpufreq working on msm8974 I've found an issue with > clock rates above 2.11GHz (e.g. 2.15GHz). When a rate above this > threshold gets requested the lowest possible frequency will be selected. > > This is caused by an overflow of the "long" return type of .round_rate > which has a maximum value of 2147483647 (2.14GHz) on 32-bit systems, > which msm8974 is. > > [...] Applied, thanks! [1/2] clk: qcom: clk-krait: switch to .determine_rate commit: a7074c3eb26e0193f2c6ed79987e633b7578024e [2/2] clk: qcom: clk-hfpll: switch to .determine_rate commit: 04648b8fad219599ccc9b103188a38e72d339a3d Best regards,
While trying to get cpufreq working on msm8974 I've found an issue with clock rates above 2.11GHz (e.g. 2.15GHz). When a rate above this threshold gets requested the lowest possible frequency will be selected. This is caused by an overflow of the "long" return type of .round_rate which has a maximum value of 2147483647 (2.14GHz) on 32-bit systems, which msm8974 is. We can switch the drivers to determine_rate so we can use the full "unsigned long" type which lets us go up to 4294967295 (4.29GHz) before an overflow happens which is significantly below the maximum frequency of any msm8974 which is around 2.45GHz. Note, that while setting the main hfpll now works correctly, the code setting the div2 is still sort of broken, since it's requesting "req->rate * 2" which will still overflow the unsigned long maximum value, but it seems this doesn't actually break anything since the div2 doesn't use the calculated value. That's my understanding at least. Signed-off-by: Luca Weiss <luca@z3ntu.xyz> --- Luca Weiss (2): clk: qcom: clk-krait: switch to .determine_rate clk: qcom: clk-hfpll: switch to .determine_rate drivers/clk/qcom/clk-hfpll.c | 14 +++++++------- drivers/clk/qcom/clk-krait.c | 10 +++++----- 2 files changed, 12 insertions(+), 12 deletions(-) --- base-commit: 6ba8a227fd19d19779005fb66ad7562608e1df83 change-id: 20230212-clk-qcom-determine_rate-c90c9ad0b337 Best regards,