From: Viresh Kumar <viresh.kumar@linaro.org>
To: Sumit Gupta <sumitg@nvidia.com>
Cc: rjw@rjwysocki.net, sudeep.holla@arm.com,
thierry.reding@gmail.com, jonathanh@nvidia.com,
linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, ksitaraman@nvidia.com,
bbasu@nvidia.com
Subject: Re: [PATCH v2 1/2] cpufreq: tegra194: get consistent cpuinfo_cur_freq
Date: Mon, 12 Oct 2020 10:52:27 +0530 [thread overview]
Message-ID: <20201012052227.x3bigztr7fit4jdz@vireshk-i7> (raw)
In-Reply-To: <1602162066-26442-2-git-send-email-sumitg@nvidia.com>
On 08-10-20, 18:31, Sumit Gupta wrote:
> Frequency returned by 'cpuinfo_cur_freq' using counters is not fixed
> and keeps changing slightly. This change returns a consistent value
> from freq_table. If the reconstructed frequency has acceptable delta
> from the last written value, then return the frequency corresponding
> to the last written ndiv value from freq_table. Otherwise, print a
> warning and return the reconstructed freq.
>
> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
> ---
> drivers/cpufreq/tegra194-cpufreq.c | 71 +++++++++++++++++++++++++++++++++-----
> 1 file changed, 62 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/cpufreq/tegra194-cpufreq.c b/drivers/cpufreq/tegra194-cpufreq.c
> index e1d931c..d250e49 100644
> --- a/drivers/cpufreq/tegra194-cpufreq.c
> +++ b/drivers/cpufreq/tegra194-cpufreq.c
> @@ -180,9 +180,70 @@ static unsigned int tegra194_get_speed_common(u32 cpu, u32 delay)
> return (rate_mhz * KHZ); /* in KHz */
> }
>
> +static void get_cpu_ndiv(void *ndiv)
> +{
> + u64 ndiv_val;
> +
> + asm volatile("mrs %0, s3_0_c15_c0_4" : "=r" (ndiv_val) : );
> +
> + *(u64 *)ndiv = ndiv_val;
> +}
> +
> +static void set_cpu_ndiv(void *data)
You weren't required to do this unnecessary change.
> +{
> + struct cpufreq_frequency_table *tbl = data;
> + u64 ndiv_val = (u64)tbl->driver_data;
> +
> + asm volatile("msr s3_0_c15_c0_4, %0" : : "r" (ndiv_val));
> +}
> +
> static unsigned int tegra194_get_speed(u32 cpu)
> {
> - return tegra194_get_speed_common(cpu, US_DELAY);
> + struct tegra194_cpufreq_data *data = cpufreq_get_driver_data();
> + struct cpufreq_frequency_table *pos;
> + unsigned int rate;
> + u64 ndiv;
> + int ret;
> + u32 cl;
> +
> + if (!cpu_online(cpu))
This isn't required. The CPU is guaranteed to be online here.
> + return -EINVAL;
> +
> + smp_call_function_single(cpu, get_cpu_cluster, &cl, true);
> +
> + if (cl >= data->num_clusters)
Is it really possible here ? I meant you must have already checked
this at cpufreq-init level already. Else mark it unlikely at least.
> + return -EINVAL;
> +
> + /* reconstruct actual cpu freq using counters */
> + rate = tegra194_get_speed_common(cpu, US_DELAY);
> +
> + /* get last written ndiv value */
> + ret = smp_call_function_single(cpu, get_cpu_ndiv, &ndiv, true);
> + if (ret) {
What exactly can fail here ? get_cpu_ndiv() can't fail. Do we really
need this check ? What about WARN_ON_ONCE() ?
> + pr_err("cpufreq: Failed to get ndiv for CPU%d, ret:%d\n",
> + cpu, ret);
> + return rate;
> + }
> +
> + /*
> + * If the reconstructed frequency has acceptable delta from
> + * the last written value, then return freq corresponding
> + * to the last written ndiv value from freq_table. This is
> + * done to return consistent value.
> + */
> + cpufreq_for_each_valid_entry(pos, data->tables[cl]) {
> + if (pos->driver_data != ndiv)
> + continue;
> +
> + if (abs(pos->frequency - rate) > 115200) {
where does this 115200 comes from ? Strange that it matches tty's baud
rate :)
This is 115 MHz, right ? Isn't that too big of a delta ?
> + pr_warn("cpufreq: cpu%d,cur:%u,set:%u,set ndiv:%llu\n",
> + cpu, rate, pos->frequency, ndiv);
> + } else {
> + rate = pos->frequency;
> + }
> + break;
> + }
> + return rate;
> }
--
viresh
next prev parent reply other threads:[~2020-10-12 5:22 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-08 13:01 [PATCH v2 0/2] Tegra194 cpufreq driver misc changes Sumit Gupta
2020-10-08 13:01 ` [PATCH v2 1/2] cpufreq: tegra194: get consistent cpuinfo_cur_freq Sumit Gupta
2020-10-12 5:22 ` Viresh Kumar [this message]
2020-10-12 16:34 ` Sumit Gupta
2020-10-08 13:01 ` [PATCH v2 2/2] cpufreq: tegra194: Fix unlisted boot freq warning Sumit Gupta
2020-10-12 6:13 ` Viresh Kumar
2020-10-12 17:06 ` Sumit Gupta
2020-10-13 5:13 ` Viresh Kumar
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