Re: [PATCH 3/3] mmc: block: Enable runtime pm for mmc blkdevice

Ulf Hansson
2013-03-06T06:57:27Z

On 6 March 2013 02:04, Asutosh Das <asutoshd@codeaurora.org> wrote:
> On 3/5/2013 7:09 AM, Ulf Hansson wrote:
>>
>> On 4 March 2013 21:48, Asutosh Das <asutoshd@codeaurora.org> wrote:
>>>
>>> On 3/1/2013 6:17 PM, Ulf Hansson wrote:
>>>>
>>>> From: Ulf Hansson <ulf.hansson@linaro.org>
>>>>
>>>> Once the mmc blkdevice is being probed, runtime pm will be enabled.
>>>> By using runtime autosuspend, the power save operations can be done
>>>> when request inactivity occurs for a certain time. Right now the
>>>> selected timeout value is set to 3 s.
>>>>
>>>> Moreover, when the blk device is being suspended, we make sure the
>>>> device
>>>> will be runtime resumed. The reason for doing this is that we what the
>>>> host suspend sequence to be unaware of any runtime power save
>>>> operations,
>>>> so it can just handle the suspend as the device is fully powerered from
>>>> a
>>>> runtime perspective.
>>>>
>>>> This patch is preparing to make it possible to move BKOPS handling into
>>>> the runtime callbacks for the mmc bus_ops. Thus IDLE BKOPS can be
>>>> accomplished.
>>>>
>>>> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>>>> ---
>>>> drivers/mmc/card/block.c | 28 ++++++++++++++++++++++++++--
>>>> 1 file changed, 26 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>>>> index 5bab73b..89d1c39 100644
>>>> --- a/drivers/mmc/card/block.c
>>>> +++ b/drivers/mmc/card/block.c
>>>> @@ -34,6 +34,7 @@
>>>> #include <linux/delay.h>
>>>> #include <linux/capability.h>
>>>> #include <linux/compat.h>
>>>> +#include <linux/pm_runtime.h>
>>>> #include <linux/mmc/ioctl.h>
>>>> #include <linux/mmc/card.h>
>>>> @@ -222,6 +223,7 @@ static ssize_t power_ro_lock_store(struct device
>>>> *dev,
>>>> md = mmc_blk_get(dev_to_disk(dev));
>>>> card = md->queue.card;
>>>> + pm_runtime_get_sync(&card->dev);
>>>> mmc_claim_host(card->host);
>>>> ret = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_BOOT_WP,
>>>> @@ -234,6 +236,8 @@ static ssize_t power_ro_lock_store(struct device
>>>> *dev,
>>>> card->ext_csd.boot_ro_lock |=
>>>> EXT_CSD_BOOT_WP_B_PWR_WP_EN;
>>>> mmc_release_host(card->host);
>>>> + pm_runtime_mark_last_busy(&card->dev);
>>>> + pm_runtime_put_autosuspend(&card->dev);
>>>> if (!ret) {
>>>> pr_info("%s: Locking boot partition ro until next power
>>>> on\n",
>>>> @@ -492,6 +496,7 @@ static int mmc_blk_ioctl_cmd(struct block_device
>>>> *bdev,
>>>> mrq.cmd = &cmd;
>>>> + pm_runtime_get_sync(&card->dev);
>>>> mmc_claim_host(card->host);
>>>> err = mmc_blk_part_switch(card, md);
>>>> @@ -560,6 +565,8 @@ static int mmc_blk_ioctl_cmd(struct block_device
>>>> *bdev,
>>>> cmd_rel_host:
>>>> mmc_release_host(card->host);
>>>> + pm_runtime_mark_last_busy(&card->dev);
>>>> + pm_runtime_put_autosuspend(&card->dev);
>>>> cmd_done:
>>>> mmc_blk_put(md);
>>>> @@ -1894,9 +1901,11 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq,
>>>> struct request *req)
>>>> struct mmc_host *host = card->host;
>>>> unsigned long flags;
>>>> - if (req && !mq->mqrq_prev->req)
>>>> + if (req && !mq->mqrq_prev->req) {
>>>> + pm_runtime_get_sync(&card->dev);
>>>> /* claim host only for the first request */
>>>> mmc_claim_host(card->host);
>>>> + }
>>>> ret = mmc_blk_part_switch(card, md);
>>>> if (ret) {
>>>> @@ -1932,9 +1941,13 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq,
>>>> struct request *req)
>>>> }
>>>> out:
>>>> - if (!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST))
>>>> + if (!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST)) {
>>>> /* release host only when there are no more requests */
>>>> mmc_release_host(card->host);
>>>> + pm_runtime_mark_last_busy(&card->dev);
>>>> + pm_runtime_put_autosuspend(&card->dev);
>>>> + }
>>>> +
>>>> return ret;
>>>> }
>>>> @@ -2331,6 +2344,12 @@ static int mmc_blk_probe(struct mmc_card
>>>> *card)
>>>> if (mmc_add_disk(part_md))
>>>> goto out;
>>>> }
>>>> +
>>>> + pm_runtime_set_active(&card->dev);
>>>> + pm_runtime_set_autosuspend_delay(&card->dev, 3000);
>>>> + pm_runtime_use_autosuspend(&card->dev);
>>>> + pm_runtime_enable(&card->dev);
>>>> +
>>>> return 0;
>>>> out:
>>>> @@ -2344,9 +2363,12 @@ static void mmc_blk_remove(struct mmc_card *card)
>>>> struct mmc_blk_data *md = mmc_get_drvdata(card);
>>>> mmc_blk_remove_parts(card, md);
>>>> + pm_runtime_get_sync(&card->dev);
>>>> mmc_claim_host(card->host);
>>>> mmc_blk_part_switch(card, md);
>>>> mmc_release_host(card->host);
>>>> + pm_runtime_disable(&card->dev);
>>>> + pm_runtime_put_noidle(&card->dev);
>>>> mmc_blk_remove_req(md);
>>>> mmc_set_drvdata(card, NULL);
>>>> }
>>>> @@ -2358,6 +2380,7 @@ static int mmc_blk_suspend(struct mmc_card *card)
>>>> struct mmc_blk_data *md = mmc_get_drvdata(card);
>>>> if (md) {
>>>> + pm_runtime_get_sync(&card->dev);
>>>> mmc_queue_suspend(&md->queue);
>>>> list_for_each_entry(part_md, &md->part, part) {
>>>> mmc_queue_suspend(&part_md->queue);
>>>> @@ -2381,6 +2404,7 @@ static int mmc_blk_resume(struct mmc_card *card)
>>>> list_for_each_entry(part_md, &md->part, part) {
>>>> mmc_queue_resume(&part_md->queue);
>>>> }
>>>> + pm_runtime_put(&card->dev);
>>>> }
>>>> return 0;
>>>> }
>>
>> Hi Asutosh,
>>
>>
>>> Hi Ulf
>>> Currently, I am implementing a patch that facilitates each device to
>>> manage
>>> is runtime pm on its own.
>>> I am using the parent-child relationship that is already established in
>>> the
>>> mmc stack for this implementation. In this case,
>>> mmc_card is a child of mmc_host which is in turn is the child of
>>> platform-device.
>>> The following contexts exist which would have to invoke get_sync and
>>> put_sync on the mmc_card device:
>>> 1. mmcqd
>>> 2. bkops
>>> 3. mmc_rescan
>>>
>>> The get_sync on card device would resume all the 3 devices starting from
>>> the
>>> platform-device and the put-sync would suspend all the 3 devices starting
>>> from the card-device.
>>> pm_auto_suspend/pm_schedule_suspend may be used to trigger the suspend
>>> from
>>> the above contexts.
>>> I believe this would simplify the runtime pm functionality.
>>>
>>> I can put up the patch for review in a couple of days.
>>>
>>> Please let me know your opinion about this approach.
>>
>> No, I don't think this is way of doing it. I will try to elaborate a
>> bit with the approach I took in my patchset and why.
>>
>> First of all, the host platform device must be kept separate (no
>> parent/child and not the same bus) from the card device. There is many
>> reason to why, but within this context (runtime pm point of view), the
>> host must be able to handle it's runtime pm resources completely
>> separate from the blk device (card device) runtime resources. More
>> precisely and from a BKOPS point of view; while doing BKOPS the host
>> platform device must still be able to enter runtime power save states.
>>
>> I realize that in your case, you are doing mmc_suspend|resume_host in
>> your host drivers runtime callbacks, which is kind of a very special
>> case, though worth to consider of course. There are two solutions to
>> enable the option for this functionality. In both cases a host caps
>> flag will be needed to enable this.
>>
>> 1.
>> In mmc bus_ops runtime callback, do a pm_runtime_get_sync("host plf
>> device"), and vice verse in the runtime resume callback. This will
>> prevent the host driver from entering runtime power save sate while
>> for example doing BKOPS, thus preventing your host driver from doing
>> mmc_suspend_host while BKOPS is running.
>>
>> 2.
>> Move mmc_suspend|resume_host from your host runtime callbacks, into
>> the bus_ops runtime callbacks. Typically, when no BKOPS is needed
>> mmc_suspend_host can be done.
>>
>> What are you thoughts around this?
>>
>> Kind regards
>> Ulf Hansson
>>
>>
>>> --
>>> Thanks
>>> Asutosh
>>>
>>> --
>>> Sent by a consultant of the Qualcomm Innovation Center, Inc.
>>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
>>> Forum.
>>>
> Hi Ulf,
> Typically, when the pltfm device enters power-save during bkops, it can only
> shut-off the clocks to the card (?), the power would still be on.
> With clock-gating in place, this would be done anyhow.

Clock gating is only one of the things you might want to do.

For example;

Your host plf device can reside in a power domain.
You might want to save power by doing pinctrl.
Disable/enable irqs.
Etc.

So, to conclude it's is realy important runtime pm for the block
device (card device) is kept separate from the host plf device.
They do handle completly different stuff.

>
> I wanted to separate the functionality as detailed below:
>
> Say we do aggressive power management: (invoke mmc_[suspend/resume]_host in
> runtime pm as well), idle-timeout of 10 s (configurable though)
>
> during suspend of mmc_card device:
> - do all card related power management, like power-off notifications etc.
>
> during suspend of mmc_host device:
> - do all the host related power management, like power-off host, shut-off
> clocks etc.
>
> during suspend of pltfm device:
> - do all the pltfm specific power management, like disable irqs, configure
> wake-ups etc.
>
> During system-suspend, it can be checked if the device is runtime-suspended,
> if yes, return.
>
> On resume, the above path would be retraced in the reverse order.
>
> I think each bus can be responsible for suspending its devices during system
> suspend.

According to my comment above, I don't think this sequence will be possible.

>
>
>>> First of all, the host platform device must be kept separate (no
>>> parent/child and not the same bus) from the card device.
> Can you please elaborate on this point a bit.

See above comment for what actions a host plf device can do at runtime
power management.

>
> I guess you would be joining the IRC chat tomorrow, if yes, we can discuss
> there itself.

It wont be possible for me to joing IRC today, I am at Hongkong with
Linaro Connect this week. Although it seems like a good discussion on
IRC, I suppose it would help to clarify on this topic.

>
>
> --
> Sent by a consultant of the Qualcomm Innovation Center, Inc.
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
>

Kind regards
Ulf Hansson