Re: [PATCH V4 16/17] platform/x86/intel/pmc: Add debug attribute for Die C6 counter

Ilpo Järvinen
2023-10-23T16:32:10Z

On Wed, 18 Oct 2023, David E. Box wrote:

> Add a "die_c6_us_show" debugfs attribute. Reads the counter value using
> Intel Platform Monitoring Technology (PMT) driver API. This counter is
> useful for determining the idle residency of CPUs in the compute tile.
>
> Signed-off-by: David E. Box <david.e.box@linux.intel.com>
> ---
> V4 - no change
>
> V3 - Split previous PATCH V2 13. Separates implementation (this patch) from
> platform specific use (next patch)
>
> V2 - Remove use of __func__
> - Use HZ_PER_MHZ
> - Fix missing newlines in printks
>
> drivers/platform/x86/intel/pmc/core.c | 55 +++++++++++++++++++++++++++
> drivers/platform/x86/intel/pmc/core.h | 4 ++
> 2 files changed, 59 insertions(+)
>
> diff --git a/drivers/platform/x86/intel/pmc/core.c b/drivers/platform/x86/intel/pmc/core.c
> index fcb0dc702aea..02f3e909cf22 100644
> --- a/drivers/platform/x86/intel/pmc/core.c
> +++ b/drivers/platform/x86/intel/pmc/core.c
> @@ -20,6 +20,7 @@
> #include <linux/pci.h>
> #include <linux/slab.h>
> #include <linux/suspend.h>
> +#include <linux/units.h>
>
> #include <asm/cpu_device_id.h>
> #include <asm/intel-family.h>
> @@ -27,6 +28,7 @@
> #include <asm/tsc.h>
>
> #include "core.h"
> +#include "../pmt/telemetry.h"
>
> /* Maximum number of modes supported by platfoms that has low power mode capability */
> const char *pmc_lpm_modes[] = {
> @@ -822,6 +824,47 @@ static int pmc_core_substate_req_regs_show(struct seq_file *s, void *unused)
> }
> DEFINE_SHOW_ATTRIBUTE(pmc_core_substate_req_regs);
>
> +static unsigned int pmc_core_get_crystal_freq(void)
> +{
> + unsigned int eax_denominator, ebx_numerator, ecx_hz, edx;
> +
> + if (boot_cpu_data.cpuid_level < 0x15)
> + return 0;
> +
> + eax_denominator = ebx_numerator = ecx_hz = edx = 0;
> +
> + /* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */
> + cpuid(0x15, &eax_denominator, &ebx_numerator, &ecx_hz, &edx);
> +
> + if (ebx_numerator == 0 || eax_denominator == 0)
> + return 0;
> +
> + return ecx_hz;
> +}
> +
> +static int pmc_core_die_c6_us_show(struct seq_file *s, void *unused)
> +{
> + struct pmc_dev *pmcdev = s->private;
> + u64 die_c6_res, count;
> + int ret;
> +
> + if (!pmcdev->crystal_freq) {
> + dev_warn_once(&pmcdev->pdev->dev, "Bad crystal frequency\n");

Isn't it more like crystal frequency is not provided rather than bad
frequency?

> + return -EINVAL;

-EINVAL is not good value to return here since there was nothing wrong
with the input. Maybe -ENXIO would be better.

> + }
> +
> + ret = pmt_telem_read(pmcdev->punit_ep, pmcdev->die_c6_offset,
> + &count, 1);
> + if (ret)
> + return ret;
> +
> + die_c6_res = div64_u64(count * HZ_PER_MHZ, pmcdev->crystal_freq);
> + seq_printf(s, "%llu\n", die_c6_res);
> +
> + return 0;
> +}
> +DEFINE_SHOW_ATTRIBUTE(pmc_core_die_c6_us);
> +
> static int pmc_core_lpm_latch_mode_show(struct seq_file *s, void *unused)
> {
> struct pmc_dev *pmcdev = s->private;
> @@ -1118,6 +1161,12 @@ static void pmc_core_dbgfs_register(struct pmc_dev *pmcdev)
> pmcdev->dbgfs_dir, pmcdev,
> &pmc_core_substate_req_regs_fops);
> }
> +
> + if (pmcdev->has_die_c6) {
> + debugfs_create_file("die_c6_us_show", 0444,
> + pmcdev->dbgfs_dir, pmcdev,
> + &pmc_core_die_c6_us_fops);
> + }
> }
>
> static const struct x86_cpu_id intel_pmc_core_ids[] = {
> @@ -1212,6 +1261,10 @@ static void pmc_core_clean_structure(struct platform_device *pdev)
> pci_dev_put(pmcdev->ssram_pcidev);
> pci_disable_device(pmcdev->ssram_pcidev);
> }
> +
> + if (pmcdev->punit_ep)
> + pmt_telem_unregister_endpoint(pmcdev->punit_ep);
> +
> platform_set_drvdata(pdev, NULL);
> mutex_destroy(&pmcdev->lock);
> }
> @@ -1232,6 +1285,8 @@ static int pmc_core_probe(struct platform_device *pdev)
> if (!pmcdev)
> return -ENOMEM;
>
> + pmcdev->crystal_freq = pmc_core_get_crystal_freq();
> +
> platform_set_drvdata(pdev, pmcdev);
> pmcdev->pdev = pdev;
>
> diff --git a/drivers/platform/x86/intel/pmc/core.h b/drivers/platform/x86/intel/pmc/core.h
> index 85b6f6ae4995..6d7673145f90 100644
> --- a/drivers/platform/x86/intel/pmc/core.h
> +++ b/drivers/platform/x86/intel/pmc/core.h
> @@ -16,6 +16,8 @@
> #include <linux/bits.h>
> #include <linux/platform_device.h>
>
> +struct telem_endpoint;
> +

This seems unrelated to the patch.

--
i.

> #define SLP_S0_RES_COUNTER_MASK GENMASK(31, 0)
>
> #define PMC_BASE_ADDR_DEFAULT 0xFE000000
> @@ -357,6 +359,7 @@ struct pmc {
> * @devs: pointer to an array of pmc pointers
> * @pdev: pointer to platform_device struct
> * @ssram_pcidev: pointer to pci device struct for the PMC SSRAM
> + * @crystal_freq: crystal frequency from cpuid
> * @dbgfs_dir: path to debugfs interface
> * @pmc_xram_read_bit: flag to indicate whether PMC XRAM shadow registers
> * used to read MPHY PG and PLL status are available
> @@ -374,6 +377,7 @@ struct pmc_dev {
> struct dentry *dbgfs_dir;
> struct platform_device *pdev;
> struct pci_dev *ssram_pcidev;
> + unsigned int crystal_freq;
> int pmc_xram_read_bit;
> struct mutex lock; /* generic mutex lock for PMC Core */
>
>