linux-kernel - Re: [PATCH v7 3/5] remoteproc: Add support for runtime PM

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Date:   Mon, 8 Jun 2020 17:03:01 -0500
From:   Suman Anna <s-anna@...com>
To:     Paul Cercueil <paul@...pouillou.net>
CC:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Arnaud Pouliquen <arnaud.pouliquen@...com>, <od@...c.me>,
        <linux-remoteproc@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Tero Kristo <t-kristo@...com>
Subject: Re: [PATCH v7 3/5] remoteproc: Add support for runtime PM

Hi Paul,

On 5/22/20 12:11 PM, Paul Cercueil wrote:
> Hi Suman,
> 
> Le ven. 22 mai 2020 à 11:47, Suman Anna <s-anna@...com> a écrit :
>> Hi Paul,
>>
>> On 5/15/20 5:43 AM, Paul Cercueil wrote:
>>> Call pm_runtime_get_sync() before the firmware is loaded, and
>>> pm_runtime_put() after the remote processor has been stopped.
>>>
>>> Even though the remoteproc device has no PM callbacks, this allows the
>>> parent device's PM callbacks to be properly called.
>>
>> I see this patch staged now for 5.8, and the latest -next branch has 
>> broken the pm-runtime autosuspend feature we have in the OMAP 
>> remoteproc driver. See commit 5f31b232c674 ("remoteproc/omap: Add 
>> support for runtime auto-suspend/resume").
>>
>> What was the original purpose of this patch, because there can be 
>> differing backends across different SoCs.
> 
> Did you try pm_suspend_ignore_children()? It looks like it was made for 
> your use-case.

Sorry for the delay in getting back. So, using 
pm_suspend_ignore_children() does fix my current issue.

But I still fail to see the original purpose of this patch in the 
remoteproc core especially given that the core itself does not have any 
callbacks. If the sole intention was to call the parent pdev's 
callbacks, then I feel that state-machine is better managed within that 
particular platform driver itself, as the sequencing/device management 
can vary with different platform drivers.

regards
Suman

> 
> Cheers,
> -Paul
> 
>>
>> regards
>> Suman
>>
>>>
>>> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>>> ---
>>>
>>> Notes:
>>>      v2-v4: No change
>>>      v5: Move calls to prepare/unprepare to rproc_fw_boot/rproc_shutdown
>>>      v6: Instead of prepare/unprepare callbacks, use PM runtime 
>>> callbacks
>>>      v7: Check return value of pm_runtime_get_sync()
>>>
>>>   drivers/remoteproc/remoteproc_core.c | 17 ++++++++++++++++-
>>>   1 file changed, 16 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/remoteproc/remoteproc_core.c 
>>> b/drivers/remoteproc/remoteproc_core.c
>>> index a7f96bc98406..e33d1ef27981 100644
>>> --- a/drivers/remoteproc/remoteproc_core.c
>>> +++ b/drivers/remoteproc/remoteproc_core.c
>>> @@ -29,6 +29,7 @@
>>>   #include <linux/devcoredump.h>
>>>   #include <linux/rculist.h>
>>>   #include <linux/remoteproc.h>
>>> +#include <linux/pm_runtime.h>
>>>   #include <linux/iommu.h>
>>>   #include <linux/idr.h>
>>>   #include <linux/elf.h>
>>> @@ -1382,6 +1383,12 @@ static int rproc_fw_boot(struct rproc *rproc, 
>>> const struct firmware *fw)
>>>       if (ret)
>>>           return ret;
>>>   +    ret = pm_runtime_get_sync(dev);
>>> +    if (ret < 0) {
>>> +        dev_err(dev, "pm_runtime_get_sync failed: %d\n", ret);
>>> +        return ret;
>>> +    }
>>> +
>>>       dev_info(dev, "Booting fw image %s, size %zd\n", name, fw->size);
>>>         /*
>>> @@ -1391,7 +1398,7 @@ static int rproc_fw_boot(struct rproc *rproc, 
>>> const struct firmware *fw)
>>>       ret = rproc_enable_iommu(rproc);
>>>       if (ret) {
>>>           dev_err(dev, "can't enable iommu: %d\n", ret);
>>> -        return ret;
>>> +        goto put_pm_runtime;
>>>       }
>>>         rproc->bootaddr = rproc_get_boot_addr(rproc, fw);
>>> @@ -1435,6 +1442,8 @@ static int rproc_fw_boot(struct rproc *rproc, 
>>> const struct firmware *fw)
>>>       rproc->table_ptr = NULL;
>>>   disable_iommu:
>>>       rproc_disable_iommu(rproc);
>>> +put_pm_runtime:
>>> +    pm_runtime_put(dev);
>>>       return ret;
>>>   }
>>>   @@ -1840,6 +1849,8 @@ void rproc_shutdown(struct rproc *rproc)
>>>         rproc_disable_iommu(rproc);
>>>   +    pm_runtime_put(dev);
>>> +
>>>       /* Free the copy of the resource table */
>>>       kfree(rproc->cached_table);
>>>       rproc->cached_table = NULL;
>>> @@ -2118,6 +2129,9 @@ struct rproc *rproc_alloc(struct device *dev, 
>>> const char *name,
>>>         rproc->state = RPROC_OFFLINE;
>>>   +    pm_runtime_no_callbacks(&rproc->dev);
>>> +    pm_runtime_enable(&rproc->dev);
>>> +
>>>       return rproc;
>>>   }
>>>   EXPORT_SYMBOL(rproc_alloc);
>>> @@ -2133,6 +2147,7 @@ EXPORT_SYMBOL(rproc_alloc);
>>>    */
>>>   void rproc_free(struct rproc *rproc)
>>>   {
>>> +    pm_runtime_disable(&rproc->dev);
>>>       put_device(&rproc->dev);
>>>   }
>>>   EXPORT_SYMBOL(rproc_free);
>>>
>>
> 
>