Subject: Re: [PATCH] ACPI / LPSS: Add device link for CHT SD card dependency
 on I2C
To: Adrian Hunter <adrian.hunter@intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Carlo Caione <carlo@endlessm.com>
References: <1512390731-11171-1-git-send-email-adrian.hunter@intel.com>
 <a949a90b-95f5-ad89-9ee0-b7e7feaf4387@redhat.com>
 <1860f193-3300-c718-9a79-d6fb690810cf@intel.com>
From: Hans de Goede <hdegoede@redhat.com>
Message-ID: <626a88b4-cf71-fd94-d78f-3947bfc5f024@redhat.com>
Date: Mon, 4 Dec 2017 15:33:29 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.5.0
MIME-Version: 1.0
In-Reply-To: <1860f193-3300-c718-9a79-d6fb690810cf@intel.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 7577
Lines: 218

Hi,

On 04-12-17 15:30, Adrian Hunter wrote:
> On 04/12/17 15:48, Hans de Goede wrote:
>> Hi,
>>
>> Wouldn't it be easier to use the ACPI _DEP tracking for this, e.g.
> 
> It is using _DEP, see acpi_lpss_dep()
> 
>> add something like this to the the probe function:
>>
>>      struct acpi_device = ACPI_COMPANION(device);
>>
>>      if (acpi_device->dep_unmet)
>>          return -EPROBE_DEFER;
>>
>> No idea if this will work, but if it does work, using the deps described
>> in the ACPI tables seems like a better solution then hardcoding this.
> 
> That would not work because there are other devices listed in the _DEP
> method so dep_unmet is always true.  So we are left checking _DEP but only
> for specific device dependencies.

Ugh, understood thank you for explaining this. Perhaps it is a good idea
to mention in the commit message why acpi_dev->dep_unmet cannot be used
here?

Regards,

Hans


>> On 04-12-17 13:32, Adrian Hunter wrote:
>>> Some Cherry Trail boards have a dependency between the SDHCI host
>>> controller used for SD cards and an external PMIC accessed via I2C. Add a
>>> device link between the SDHCI host controller (consumer) and the I2C
>>> adapter (supplier).
>>>
>>> This patch depends on a fix to devices links, namely commit 0ff26c662d5f
>>> ("driver core: Fix device link deferred probe"). And also either,
>>> commit 126dbc6b49c8 ("PM: i2c-designware-platdrv: Clean up PM handling in
>>> probe"), or patch "PM / runtime: Fix handling of suppliers with disabled
>>> runtime PM".
>>>
>>> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
>>> ---
>>>    drivers/acpi/acpi_lpss.c | 139
>>> +++++++++++++++++++++++++++++++++++++++++++++++
>>>    1 file changed, 139 insertions(+)
>>>
>>> diff --git a/drivers/acpi/acpi_lpss.c b/drivers/acpi/acpi_lpss.c
>>> index 7f2b02cc8ea1..9d82f2f6c327 100644
>>> --- a/drivers/acpi/acpi_lpss.c
>>> +++ b/drivers/acpi/acpi_lpss.c
>>> @@ -290,6 +290,11 @@ static void bsw_pwm_setup(struct lpss_private_data
>>> *pdata)
>>>        {}
>>>    };
>>>    +static const struct x86_cpu_id cht_cpu[] = {
>>> +    ICPU(INTEL_FAM6_ATOM_AIRMONT),    /* Braswell, Cherry Trail */
>>> +    {}
>>> +};
>>> +
>>>    #else
>>>      #define LPSS_ADDR(desc) (0UL)
>>> @@ -427,6 +432,139 @@ static int register_device_clock(struct acpi_device
>>> *adev,
>>>        return 0;
>>>    }
>>>    +struct lpss_device_links {
>>> +    const char *supplier_hid;
>>> +    const char *supplier_uid;
>>> +    const char *consumer_hid;
>>> +    const char *consumer_uid;
>>> +    const struct x86_cpu_id *cpus;
>>> +    u32 flags;
>>> +};
>>> +
>>> +static const struct lpss_device_links lpss_device_links[] = {
>>> +    {"808622C1", "7", "80860F14", "3", cht_cpu, DL_FLAG_PM_RUNTIME},
>>> +};
>>> +
>>> +static bool hid_uid_match(const char *hid1, const char *uid1,
>>> +              const char *hid2, const char *uid2)
>>> +{
>>> +    return !strcmp(hid1, hid2) && uid1 && uid2 && !strcmp(uid1, uid2);
>>> +}
>>> +
>>> +static bool acpi_lpss_is_supplier(struct acpi_device *adev,
>>> +                  const struct lpss_device_links *link)
>>> +{
>>> +    return hid_uid_match(acpi_device_hid(adev), acpi_device_uid(adev),
>>> +                 link->supplier_hid, link->supplier_uid);
>>> +}
>>> +
>>> +static bool acpi_lpss_is_consumer(struct acpi_device *adev,
>>> +                  const struct lpss_device_links *link)
>>> +{
>>> +    return hid_uid_match(acpi_device_hid(adev), acpi_device_uid(adev),
>>> +                 link->consumer_hid, link->consumer_uid);
>>> +}
>>> +
>>> +struct hid_uid {
>>> +    const char *hid;
>>> +    const char *uid;
>>> +};
>>> +
>>> +static int match_hid_uid(struct device *dev, void *data)
>>> +{
>>> +    struct acpi_device *adev = ACPI_COMPANION(dev);
>>> +    struct hid_uid *id = data;
>>> +
>>> +    if (!adev)
>>> +        return 0;
>>> +
>>> +    return hid_uid_match(acpi_device_hid(adev), acpi_device_uid(adev),
>>> +                 id->hid, id->uid);
>>> +}
>>> +
>>> +static struct device *acpi_lpss_find_device(const char *hid, const char
>>> *uid)
>>> +{
>>> +    struct hid_uid data = {
>>> +        .hid = hid,
>>> +        .uid = uid,
>>> +    };
>>> +
>>> +    return bus_find_device(&platform_bus_type, NULL, &data, match_hid_uid);
>>> +}
>>> +
>>> +static bool acpi_lpss_dep(struct acpi_device *adev, acpi_handle handle)
>>> +{
>>> +    struct acpi_handle_list dep_devices;
>>> +    acpi_status status;
>>> +    int i;
>>> +
>>> +    if (!acpi_has_method(adev->handle, "_DEP"))
>>> +        return false;
>>> +
>>> +    status = acpi_evaluate_reference(adev->handle, "_DEP", NULL,
>>> +                     &dep_devices);
>>> +    if (ACPI_FAILURE(status)) {
>>> +        dev_dbg(&adev->dev, "Failed to evaluate _DEP.\n");
>>> +        return false;
>>> +    }
>>> +
>>> +    for (i = 0; i < dep_devices.count; i++) {
>>> +        if (dep_devices.handles[i] == handle)
>>> +            return true;
>>> +    }
>>> +
>>> +    return false;
>>> +}
>>> +
>>> +static void acpi_lpss_link_consumer(struct device *dev1,
>>> +                    const struct lpss_device_links *link)
>>> +{
>>> +    struct device *dev2;
>>> +
>>> +    dev2 = acpi_lpss_find_device(link->consumer_hid, link->consumer_uid);
>>> +    if (!dev2)
>>> +        return;
>>> +
>>> +    if (acpi_lpss_dep(ACPI_COMPANION(dev2), ACPI_HANDLE(dev1)))
>>> +        device_link_add(dev2, dev1, link->flags);
>>> +
>>> +    put_device(dev2);
>>> +}
>>> +
>>> +static void acpi_lpss_link_supplier(struct device *dev1,
>>> +                    const struct lpss_device_links *link)
>>> +{
>>> +    struct device *dev2;
>>> +
>>> +    dev2 = acpi_lpss_find_device(link->supplier_hid, link->supplier_uid);
>>> +    if (!dev2)
>>> +        return;
>>> +
>>> +    if (acpi_lpss_dep(ACPI_COMPANION(dev1), ACPI_HANDLE(dev2)))
>>> +        device_link_add(dev1, dev2, link->flags);
>>> +
>>> +    put_device(dev2);
>>> +}
>>> +
>>> +static void acpi_lpss_create_device_links(struct acpi_device *adev,
>>> +                      struct platform_device *pdev)
>>> +{
>>> +    int i;
>>> +
>>> +    for (i = 0; i < ARRAY_SIZE(lpss_device_links); i++) {
>>> +        const struct lpss_device_links *link = &lpss_device_links[i];
>>> +
>>> +        if (link->cpus && !x86_match_cpu(link->cpus))
>>> +            continue;
>>> +
>>> +        if (acpi_lpss_is_supplier(adev, link))
>>> +            acpi_lpss_link_consumer(&pdev->dev, link);
>>> +
>>> +        if (acpi_lpss_is_consumer(adev, link))
>>> +            acpi_lpss_link_supplier(&pdev->dev, link);
>>> +    }
>>> +}
>>> +
>>>    static int acpi_lpss_create_device(struct acpi_device *adev,
>>>                       const struct acpi_device_id *id)
>>>    {
>>> @@ -500,6 +638,7 @@ static int acpi_lpss_create_device(struct acpi_device
>>> *adev,
>>>        adev->driver_data = pdata;
>>>        pdev = acpi_create_platform_device(adev, dev_desc->properties);
>>>        if (!IS_ERR_OR_NULL(pdev)) {
>>> +        acpi_lpss_create_device_links(adev, pdev);
>>>            return 1;
>>>        }
>>>   
>>
>