linux-kernel - Re: [PATCH v5 7/7] iommu/exynos: Use device dependency links to control runtime pm

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Message-id: <7a69ca4e-e276-1bdc-edf2-b881a91f820a@samsung.com>
Date:   Mon, 24 Oct 2016 07:30:12 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Sricharan <sricharan@...eaurora.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-samsung-soc@...r.kernel.org
Cc:     'Tomeu Vizoso' <tomeu.vizoso@...labora.com>,
        'Bartlomiej Zolnierkiewicz' <b.zolnierkie@...sung.com>,
        'Greg Kroah-Hartman' <gregkh@...uxfoundation.org>,
        'Kevin Hilman' <khilman@...nel.org>,
        "'Rafael J. Wysocki'" <rjw@...ysocki.net>,
        'Tomasz Figa' <tomasz.figa@...il.com>,
        'Krzysztof Kozlowski' <krzk@...nel.org>,
        'Inki Dae' <inki.dae@...sung.com>,
        'Tobias Jakobi' <tjakobi@...h.uni-bielefeld.de>,
        "'Luis R. Rodriguez'" <mcgrof@...nel.org>,
        'Kukjin Kim' <kgene@...nel.org>,
        'Mark Brown' <broonie@...nel.org>,
        'Lukas Wunner' <lukas@...ner.de>
Subject: Re: [PATCH v5 7/7] iommu/exynos: Use device dependency links to
 control runtime pm

Hi Sricharan,


On 2016-10-23 11:49, Sricharan wrote:
> Hi Marek,
>> This patch uses recently introduced device dependency links to track the
>> runtime pm state of the master's device. This way each SYSMMU controller
>> is set to runtime active only when its master's device is active and can
>> restore or save its state instead of being activated all the time when
>> attached to the given master device. This way SYSMMU controllers no longer
>> prevents respective power domains to be turned off when master's device
>> is not being used.
>>
>> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
>> ---
>> drivers/iommu/exynos-iommu.c | 16 ++++++++--------
>> 1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
>> index 5e6d7bbf9b70..59b4f2ce4f5f 100644
>> --- a/drivers/iommu/exynos-iommu.c
>> +++ b/drivers/iommu/exynos-iommu.c
>> @@ -781,10 +781,6 @@ static void exynos_iommu_detach_device(struct iommu_domain *iommu_domain,
>> 	if (!has_sysmmu(dev) || owner->domain != iommu_domain)
>> 		return;
>>
>> -	list_for_each_entry(data, &owner->controllers, owner_node) {
>> -		pm_runtime_put_sync(data->sysmmu);
>> -	}
>> -
>> 	mutex_lock(&owner->rpm_lock);
>>
>> 	list_for_each_entry(data, &owner->controllers, owner_node) {
>> @@ -848,10 +844,6 @@ static int exynos_iommu_attach_device(struct iommu_domain *iommu_domain,
>>
>> 	mutex_unlock(&owner->rpm_lock);
>>
>> -	list_for_each_entry(data, &owner->controllers, owner_node) {
>> -		pm_runtime_get_sync(data->sysmmu);
>> -	}
>> -
>> 	dev_dbg(dev, "%s: Attached IOMMU with pgtable %pa\n", __func__,
>> 		&pagetable);
>>
>> @@ -1232,6 +1224,14 @@ static int exynos_iommu_of_xlate(struct device *dev,
>>
>> 	list_add_tail(&data->owner_node, &owner->controllers);
>> 	data->master = dev;
>> +
>> +	/*
>> +	 * SYSMMU will be runtime activated via device link (dependency) to its
>> +	 * master device, so there are no direct calls to pm_runtime_get/put
>> +	 * in this driver.
>> +	 */
>> +	device_link_add(dev, data->sysmmu, DL_FLAG_PM_RUNTIME);
>> +
>    So in the case of master with multiple sids, this would be called multiple times
>    for the same master ?

I don't know what is "multiple sids" case, but if given SYSMMU master 
device (supplier)
has multiple SYSMMU controllers (consumers), then links will be created 
for each SYSMMU
controller. Please note that this code is based on vanilla v4.9-rc1, 
which calls
of_xlate() callback only once for every iommu for given master device. 
Your IOMMU
deferred probe patches change this, but I already posted a fix for 
Exynos IOMMU driver
to handle such case.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland