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Subject: Re: [PATCH 1/2] platform/x86: intel_pmc_core: Convert to a
 platform_driver
To:     Rajat Jain <rajatja@google.com>
Cc:     Rajat Jain <rajatxjain@gmail.com>,
        Rajneesh Bhardwaj <rajneesh.bhardwaj@intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@intel.com>,
        Vishwanath Somayaji <vishwanath.somayaji@intel.com>,
        Darren Hart <dvhart@infradead.org>,
        Andy Shevchenko <andy@infradead.org>,
        Platform Driver <platform-driver-x86@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Furquan Shaikh <furquan@google.com>,
        Evan Green <evgreen@google.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        "Box, David E" <david.e.box@intel.com>
References: <20190313222124.229371-1-rajatja@google.com>
 <20190316081752.GA21812@raj-desk2.iind.intel.com>
 <CAA93t1qoQx2B9=KuNpuXL_PvdpgGJPzZk8N-KWqS4XyO8qrS5g@mail.gmail.com>
 <3fc03e60-492a-e9b5-ac9b-caa17f8a8e27@linux.intel.com>
 <CACK8Z6HGEeM_0AnM1eJcUgNPwFz6_wsT8oFAG2rkV4UZczDi3g@mail.gmail.com>
From:   "Bhardwaj, Rajneesh" <rajneesh.bhardwaj@linux.intel.com>
Message-ID: <c98af2ef-5800-0dee-7b58-3be48f612d07@linux.intel.com>
Date:   Mon, 25 Mar 2019 15:53:23 +0530
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Hi Rajat

On 23-Mar-19 6:00 AM, Rajat Jain wrote:
> Hi Rajneesh,
>
>
>
> On Fri, Mar 22, 2019 at 12:56 PM Bhardwaj, Rajneesh
> <rajneesh.bhardwaj@linux.intel.com> wrote:
>> Some suggestions below
>>
>> On 18-Mar-19 8:36 PM, Rajat Jain wrote:
>>
>> On Sat, Mar 16, 2019 at 1:30 AM Rajneesh Bhardwaj
>> <rajneesh.bhardwaj@intel.com> wrote:
>>
>> On Wed, Mar 13, 2019 at 03:21:23PM -0700, Rajat Jain wrote:
>>
>> Convert the intel_pmc_core driver to a platform driver. There is no
>> functional change. Some code that tries to determine what kind of
>> CPU this is, has been moved code is moved from pmc_core_probe() to
>>
>> Possible typo here.
>>
>> Ummm, you mean grammar error I guess? Sure, I will rephrase.
>>
>> pmc_core_init().
>>
>> Signed-off-by: Rajat Jain <rajatja@google.com>
>>
>> Thanks for sending this. This is certainly useful to support suspend-resume
>> functionality for this driver which is otherwise only possible with PM
>> notifiers otherwise and that is not desirable. Initially this was a PCI
>> driver and after design discussion it was converted to module. I would like
>> to consult Andy and Srinivas for their opinion about binding it to actual
>> platform bus instead of the virtual bus as in its current form. In one of the
>> internal versions, we used a known acpi PNP HID.
>>
>> Sure, if there is an established ACPI PNP HID, then we could bind it
>> using that, on platforms where we are still developing BIOS /
>> coreboot. However, this might not be possible for shipping systems
>> (Kabylake / skylake) where there is no plan to change the BIOS.
>>
>> In one of our internal patches, i had used HID of power engine plugin. IIRC, During my testing it was working on KBL, CNL with UEFI BIOS but i highly recommend testing it.
>>
>> ---8<----8<-----
>>
>> +static const struct acpi_device_id pmc_acpi_ids[] = {
>>
>> +             {"INT33A1", 0}, /* _HID for Intel Power Engine, _CID PNP0D80*/
>>
>> +             { }
>>
>>   };
> We do not have this device in any of our ACPI tables today. If Intel
> can confirm that this is a well known HID to be used for attaching
> this driver, we can start putting it on our platform's ACPI going
> forward (Whiskeylake, Cometlake, Cannonlake, Icelake ...). But I
> believe we also need to have this driver attach with the device on
> older platforms (Skylake, Kabylake, Amberlake) that are already
> shipping, and running a Non UEFI BIOS (that may not have this HID
> since it is not published).
>
> Currently the intel_pmc_core driver attaches itself to the following
> table of CPU families, without regard to whether it has that HID in
> the ACPI or not:
>
> static const struct x86_cpu_id intel_pmc_core_ids[] = {
>          INTEL_CPU_FAM6(SKYLAKE_MOBILE, spt_reg_map),
>          INTEL_CPU_FAM6(SKYLAKE_DESKTOP, spt_reg_map),
>          INTEL_CPU_FAM6(KABYLAKE_MOBILE, spt_reg_map),
>          INTEL_CPU_FAM6(KABYLAKE_DESKTOP, spt_reg_map),
>          INTEL_CPU_FAM6(CANNONLAKE_MOBILE, cnp_reg_map),
>          INTEL_CPU_FAM6(ICELAKE_MOBILE, icl_reg_map),
>          {}
> };

In the past i tried one hybrid approach i.e. PCI and Platform driver at 
the same time. Based on that, i feel that this idea of spilling probe 
like this may not be the best option. The ACPI CID that i suggested is 
available on most Intel Core Platforms that i have worked on and i can 
help you in verifying it with UEFI BIOS if you want. Meanwhile, please 
see this https://patchwork.kernel.org/patch/9806565/ it gives some 
background about this ACPI ID and also points to the LPIT spec.

>
> So to avoid a regression, I suggest that we still maintain the above
> table (may be eliminate few entries) and always attach if the CPU is
> among the table, and if the CPU is not among the table, use the ACPI
> HID to attach. I propose to attach to at least Skylake and Kabylake
> systems using the table above, and for Canonlake and Icelake and
> newer, we can rely on BIOS providing the ACPI HID. Of course I do not
> know if all non-Google Canonlake/Icelake platforms will have this HID
> in their BIOS. If we are not sure, we can include Canonlake and
> Icelake also in that list, an. Please let me know what do you think.

If Coreboot firmware can not be updated for the shipping devices, then 
can Chromium kernel take the suggested deviation which i think gets 
updated OTA periodically? For upstream,  I am waiting to hear from 
Rafael, Andi, David and Srinivas for their inputs.

>
> Thanks,
>
> Rajat
>
>>
>>
>> -builtin_pci_driver(intel_pmc_core_driver);
>>
>> +static struct platform_driver pmc_plat_driver = {
>>
>> +             .remove = pmc_plat_remove,
>>
>> +             .probe = pmc_plat_probe,
>>
>> +             .driver = {
>>
>> +                             .name = "pmc_core_driver",
>>
>> +                             .acpi_match_table = ACPI_PTR(pmc_acpi_ids),
>>
>> +             },
>>
>> +};
>>
>> ---
>> This is rebased off
>> git://git.infradead.org/linux-platform-drivers-x86.git/for-next
>>
>>   drivers/platform/x86/intel_pmc_core.c | 93 ++++++++++++++++++++-------
>>   1 file changed, 68 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/platform/x86/intel_pmc_core.c b/drivers/platform/x86/intel_pmc_core.c
>> index f2c621b55f49..55578d07610c 100644
>> --- a/drivers/platform/x86/intel_pmc_core.c
>> +++ b/drivers/platform/x86/intel_pmc_core.c
>> @@ -19,6 +19,7 @@
>>   #include <linux/io.h>
>>   #include <linux/module.h>
>>   #include <linux/pci.h>
>> +#include <linux/platform_device.h>
>>   #include <linux/uaccess.h>
>>
>>   #include <asm/cpu_device_id.h>
>> @@ -854,12 +855,59 @@ static const struct dmi_system_id pmc_core_dmi_table[]  = {
>>        {}
>>   };
>>
>> -static int __init pmc_core_probe(void)
>> +static int pmc_core_probe(struct platform_device *pdev)
>>   {
>> -     struct pmc_dev *pmcdev = &pmc;
>> +     struct pmc_dev *pmcdev = platform_get_drvdata(pdev);
>> +     int err;
>> +
>> +     pmcdev->regbase = ioremap(pmcdev->base_addr,
>> +                               pmcdev->map->regmap_length);
>> +     if (!pmcdev->regbase)
>> +             return -ENOMEM;
>> +
>> +     mutex_init(&pmcdev->lock);
>> +     pmcdev->pmc_xram_read_bit = pmc_core_check_read_lock_bit();
>> +
>> +     err = pmc_core_dbgfs_register(pmcdev);
>> +     if (err < 0) {
>> +             dev_warn(&pdev->dev, "debugfs register failed.\n");
>> +             iounmap(pmcdev->regbase);
>> +             return err;
>> +     }
>> +
>> +     dmi_check_system(pmc_core_dmi_table);
>> +     dev_info(&pdev->dev, " initialized\n");
>> +     return 0;
>> +}
>> +
>> +static int pmc_core_remove(struct platform_device *pdev)
>> +{
>> +     struct pmc_dev *pmcdev = platform_get_drvdata(pdev);
>> +
>> +     pmc_core_dbgfs_unregister(pmcdev);
>> +     mutex_destroy(&pmcdev->lock);
>> +     iounmap(pmcdev->regbase);
>> +     return 0;
>> +}
>> +
>> +static struct platform_driver pmc_core_driver = {
>> +     .driver = {
>> +             .name = "pmc_core",
>> +     },
>> +     .probe = pmc_core_probe,
>> +     .remove = pmc_core_remove,
>> +};
>> +
>> +static struct platform_device pmc_core_device = {
>> +     .name           = "pmc_core",
>> +};
>> +
>> +static int __init pmc_core_init(void)
>> +{
>> +     int ret;
>>
>> Please use reverse x-mas tree style.
>>
>> OK, will do.
>>
>>        const struct x86_cpu_id *cpu_id;
>> +     struct pmc_dev *pmcdev = &pmc;
>>        u64 slp_s0_addr;
>> -     int err;
>>
>>        cpu_id = x86_match_cpu(intel_pmc_core_ids);
>>        if (!cpu_id)
>> @@ -880,36 +928,31 @@ static int __init pmc_core_probe(void)
>>        else
>>                pmcdev->base_addr = slp_s0_addr - pmcdev->map->slp_s0_offset;
>>
>> -     pmcdev->regbase = ioremap(pmcdev->base_addr,
>> -                               pmcdev->map->regmap_length);
>> -     if (!pmcdev->regbase)
>> -             return -ENOMEM;
>> +     platform_set_drvdata(&pmc_core_device, pmcdev);
>>
>> -     mutex_init(&pmcdev->lock);
>> -     pmcdev->pmc_xram_read_bit = pmc_core_check_read_lock_bit();
>> +     ret = platform_device_register(&pmc_core_device);
>> +     if (ret)
>> +             return ret;
>>
>> -     err = pmc_core_dbgfs_register(pmcdev);
>> -     if (err < 0) {
>> -             pr_warn(" debugfs register failed.\n");
>> -             iounmap(pmcdev->regbase);
>> -             return err;
>> -     }
>> +     ret = platform_driver_register(&pmc_core_driver);
>> +     if (ret)
>> +             goto out_remove_dev;
>>
>> -     dmi_check_system(pmc_core_dmi_table);
>> -     pr_info(" initialized\n");
>>        return 0;
>> +
>> +out_remove_dev:
>> +     platform_device_unregister(&pmc_core_device);
>> +     return ret;
>>   }
>> -module_init(pmc_core_probe)
>>
>> -static void __exit pmc_core_remove(void)
>> +static void __init pmc_core_exit(void)
>>   {
>> -     struct pmc_dev *pmcdev = &pmc;
>> -
>> -     pmc_core_dbgfs_unregister(pmcdev);
>> -     mutex_destroy(&pmcdev->lock);
>> -     iounmap(pmcdev->regbase);
>> +     platform_driver_unregister(&pmc_core_driver);
>> +     platform_device_unregister(&pmc_core_device);
>>   }
>> -module_exit(pmc_core_remove)
>> +
>> +module_init(pmc_core_init);
>> +module_exit(pmc_core_exit);
>>
>>   MODULE_LICENSE("GPL v2");
>>   MODULE_DESCRIPTION("Intel PMC Core Driver");
>> --
>> 2.21.0.360.g471c308f928-goog
>>
>> --
>> Best Regards,
>> Rajneesh