linux-kernel - Re: [PATCH 4/4] platform/x86: intel_telemetry: report debugfs failure

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Date:   Fri, 28 Sep 2018 14:40:58 +0530
From:   Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>
To:     "Bhardwaj, Rajneesh" <rajneesh.bhardwaj@...ux.intel.com>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Souvik Kumar Chakravarty <souvik.k.chakravarty@...el.com>,
        matt.turner@...el.com, "Brown, Len" <len.brown@...el.com>,
        Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...el.com>
Subject: Re: [PATCH 4/4] platform/x86: intel_telemetry: report debugfs failure

On Fri, Sep 28, 2018 at 02:44:06PM +0530, Bhardwaj, Rajneesh wrote:

Resending it since previous message had few HTML contents so it was not
delivered to the list.

>
>
> On 26-Sep-18 10:48 PM, Andy Shevchenko wrote:
> >On Wed, Sep 26, 2018 at 5:24 PM Bhardwaj, Rajneesh
> ><rajneesh.bhardwaj@...ux.intel.com> wrote:
> >>On 26-Sep-18 7:26 PM, Andy Shevchenko wrote:
> >>>On Mon, Sep 3, 2018 at 9:05 PM Rajneesh Bhardwaj
> >>><rajneesh.bhardwaj@...ux.intel.com> wrote:
> >>>>not be obtained and result in a invalid telemetry_plt_config.
> >>>What is telemetry_plt_config?
> >>Internal data structure that holds platform config, maintained by the
> >>telemetry platform driver.
> >You need to spell if for the reader.
>
> Sure, thanks for the suggestion. I will do it if you agree to my explanation
> below and require v2.
>
> >
> >>>>This is also applicable to the platforms where the BIOS supports IPC1
> >>>>device under debug configurations but IPC1 is disabled by user or the
> >>>>policy.
> >>>>
> >>>>This change allows user to know the reason for not seeing entries under
> >>>>/sys/kernel/debug/telemetry/* when there is no apparent failure at boot.
> >>>>+exit:
> >>>>+       pr_debug(pr_fmt(DRIVER_NAME) " Failed\n");
> >>>Completely useless.
> >>>
> >>>Device core does it in generic way.
> >>If i remove this print then perhaps there is no need of this patch.
> >Maybe.
> >
> >
> >
> >>Reason to print this is that the platform driver / core driver does not
> >>show any error.
> >If the code fails and returns 0 — it's a bug in error reporting inside the code.
>

Below are my comments as per previous mail.

> The existing Telemetry ecosystem for Atom consists of IPC driver, telem core
> driver and telem platform driver but there are no consumers of the APIs
> except the ones in telem debugfs driver. Here in this case, not all drivers
> that make up the telemetry infra return failure. Here is how the system
> looks w/wo IPC1 setting in the BIOS.
>
> When IPC is present
>
> root@...-glk:~# lsmod | grep -i telem
>
> intel_telemetry_debugfs245760
>
> intel_telemetry_pltdrv204800
>
> intel_punit_ipc163841 intel_telemetry_pltdrv
>
> intel_telemetry_core163842 intel_telemetry_debugfs,intel_telemetry_pltdrv
>
> intel_pmc_ipc204802 intel_telemetry_debugfs,intel_telemetry_pltdrv
>
> When IPC is missing
>
> root@...-glk:~# lsmod | grep -i telem
>
> intel_telemetry_pltdrv204800
>
> intel_punit_ipc163841 intel_telemetry_pltdrv
>
> intel_telemetry_core163841 intel_telemetry_pltdrv
>
> intel_pmc_ipc204801 intel_telemetry_pltdrv
>
>
> If we look at the dmesg log, we see  "intel_telemetry_core Init". So one
> might think that the driver has loaded fine since user may not know that
> telemetry is more than just one driver. Such things are often reported by
> users of this driver.
> So IMHO, keeping this error helps user triage the problem easily. I can
> change to pr_info you'd like it.
>
> >
> >>In-fact they are even loaded in module table. OTOH, this
> >>debugfs interface fails. This is very confusing to the users if they
> >>check the lsmod output so i feel this print might help.
> >Again, device core *already has* this and even more (it prints also a
> >return code!).
> >
>

-- 
Best Regards,
Rajneesh