linux-kernel - Re: [PATCH v5 2/3] platform/x86: intel_pmc_core: Allow to dump debug registers on S0ix failure

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Date:   Thu, 11 Apr 2019 16:40:37 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>,
        Vishwanath Somayaji <vishwanath.somayaji@...el.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rafael J Wysocki <rafael.j.wysocki@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Furquan Shaikh <furquan@...gle.com>,
        Evan Green <evgreen@...gle.com>,
        Rajat Jain <rajatxjain@...il.com>
Subject: Re: [PATCH v5 2/3] platform/x86: intel_pmc_core: Allow to dump debug
 registers on S0ix failure

On Thu, Apr 11, 2019 at 3:38 AM Rajat Jain <rajatja@...gle.com> wrote:
>
> Add a module parameter which when enabled, will check on resume, if the
> last S0ix attempt was successful. If not, the driver would warn and provide
> helpful debug information (which gets latched during the failed suspend
> attempt) to debug the S0ix failure.
>
> This information is very useful to debug S0ix failures. Specially since
> the latched debug information will be lost (over-written) if the system
> attempts to go into runtime (or imminent) S0ix again after that failed
> suspend attempt.

> +static int pmc_core_suspend(struct device *dev)
> +{
> +       struct pmc_dev *pmcdev = dev_get_drvdata(dev);
> +
> +       pmcdev->check_counters = false;
> +
> +       /* No warnings on S0ix failures */
> +       if (!warn_on_s0ix_failures)
> +               return 0;
> +
> +       /* Check if the syspend will actually use S0ix */
> +       if (pm_suspend_via_firmware())
> +               return 0;
> +
> +       /* Save PC10 and S0ix residency for checking later */

> +       if (!rdmsrl_safe(MSR_PKG_C10_RESIDENCY, &pmcdev->pc10_counter) &&
> +           !pmc_core_dev_state_get(pmcdev, &pmcdev->s0ix_counter))

Split it.

> +               pmcdev->check_counters = true;
> +
> +       return 0;
> +}
> +
> +static inline bool pmc_core_is_pc10_failed(struct pmc_dev *pmcdev)
> +{
> +       u64 pc10_counter;
> +
> +       if (!rdmsrl_safe(MSR_PKG_C10_RESIDENCY, &pc10_counter) &&
> +           pc10_counter == pmcdev->pc10_counter)
> +               return true;

Split this as well.

> +
> +       return false;
> +}
> +
> +static inline bool pmc_core_is_s0ix_failed(struct pmc_dev *pmcdev)
> +{
> +       u64 s0ix_counter;
> +
> +       if (!pmc_core_dev_state_get(pmcdev, &s0ix_counter) &&
> +           s0ix_counter == pmcdev->s0ix_counter)
> +               return true;

And this.

> +
> +       return false;
> +}
> +
> +static int pmc_core_resume(struct device *dev)
> +{
> +       struct pmc_dev *pmcdev = dev_get_drvdata(dev);
> +
> +       if (!pmcdev->check_counters)
> +               return 0;
> +
> +       if (pmc_core_is_pc10_failed(pmcdev)) {
> +               dev_info(dev, "PC10 entry had failed (PC10 cnt=0x%llx)\n",
> +                        pmcdev->pc10_counter);
> +       } else if (pmc_core_is_s0ix_failed(pmcdev)) {

> +

Redundant.

> +               const struct pmc_bit_map **maps = pmcdev->map->slps0_dbg_maps;
> +               const struct pmc_bit_map *map;
> +               int offset = pmcdev->map->slps0_dbg_offset;
> +               u32 data;
> +
> +               dev_warn(dev, "S0ix entry had failed (S0ix cnt=%llu)\n",
> +                        pmcdev->s0ix_counter);
> +               while (*maps) {
> +                       map = *maps;
> +                       data = pmc_core_reg_read(pmcdev, offset);
> +                       offset += 4;
> +                       while (map->name) {
> +                               dev_warn(dev, "SLP_S0_DBG: %-32s\tState: %s\n",
> +                                        map->name,
> +                                        data & map->bit_mask ? "Yes" : "No");

> +                               ++map;

map++;

> +                       }
> +                       ++maps;

maps++;

> +               }

This is quite noisy. You need to print only what is important. I don't
think polluting dmesg with piles of these kind of messages is a good
idea.
Also, it is more likely should be done on debug level (except may be
one or two messages with really important information).

> +       }
> +       return 0;
> +}
> +
> +#endif

-- 
With Best Regards,
Andy Shevchenko