linux-kernel - Re: [PATCH v4 3/5] remoteproc: Add prepare/unprepare callbacks

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Message-ID: <ac16c0ee-0dd1-d383-14ed-13b360e3e79d@st.com>
Date:   Tue, 17 Dec 2019 10:21:57 +0000
From:   Fabien DESSENNE <fabien.dessenne@...com>
To:     Paul Cercueil <paul@...pouillou.net>
CC:     Ohad Ben-Cohen <ohad@...ery.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, "od@...c.me" <od@...c.me>,
        "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/5] remoteproc: Add prepare/unprepare callbacks

Hi Paul


On 14/12/2019 11:30 PM, Paul Cercueil wrote:
> Hi Fabien,
>
>
> Le jeu., déc. 12, 2019 at 10:03, Fabien DESSENNE 
> <fabien.dessenne@...com> a écrit :
>> Hi Paul
>>
>>
>> On 10/12/2019 5:40 PM, Paul Cercueil wrote:
>>>  The .prepare() callback is called before the firmware is loaded to
>>>  memory. This is useful for instance in the case where some setup is
>>>  required for the memory to be accessible.
>>
>>
>> I am trying to figure out what king of 'setup' may be required. From the
>> ingenic driver I understand that you need to enable clocks to allow some
>> memory access.
>>
>> Instead of adding this new ops, why not enabling clocks in probe()?
>
> Enabling the clocks in the probe means that the clocks will be 
> unconditionally enabled until the driver is removed, even if the 
> remote processor end up being unused. That would be a waste of power.


OK I understand.

Nevertheless I think that you may need to call .prepare() from 
rproc_fw_boot() since you may need to access some memories from the 
point rproc_handle_resources() is called (this sets up virtio which is 
used if you have a resource table defining vdev).

And rproc_fw_boot() calls rproc_enable_iommu(), which sounds like 
"prepare memory", so this may be the right place to call .prepare()


BR

Fabien


>
> Cheers,
> -Paul
>
>
>>
>> BR
>>
>> Fabien
>>
>>
>>>
>>>  Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>>>  ---
>>>
>>>  Notes:
>>>       v2-v4: No change
>>>
>>>    drivers/remoteproc/remoteproc_core.c | 16 +++++++++++++++-
>>>    include/linux/remoteproc.h           |  4 ++++
>>>    2 files changed, 19 insertions(+), 1 deletion(-)
>>>
>>>  diff --git a/drivers/remoteproc/remoteproc_core.c 
>>> b/drivers/remoteproc/remoteproc_core.c
>>>  index 0a9fc7fdd1c3..3ea5f675a148 100644
>>>  --- a/drivers/remoteproc/remoteproc_core.c
>>>  +++ b/drivers/remoteproc/remoteproc_core.c
>>>  @@ -1299,11 +1299,19 @@ static int rproc_start(struct rproc *rproc, 
>>> const struct firmware *fw)
>>>        struct device *dev = &rproc->dev;
>>>        int ret;
>>>
>>>  +    if (rproc->ops->prepare) {
>>>  +        ret = rproc->ops->prepare(rproc);
>>>  +        if (ret) {
>>>  +            dev_err(dev, "Failed to prepare rproc: %d\n", ret);
>>>  +            return ret;
>>>  +        }
>>>  +    }
>>>  +
>>>        /* load the ELF segments to memory */
>>>        ret = rproc_load_segments(rproc, fw);
>>>        if (ret) {
>>>            dev_err(dev, "Failed to load program segments: %d\n", ret);
>>>  -        return ret;
>>>  +        goto unprepare_rproc;
>>>        }
>>>
>>>        /*
>>>  @@ -1354,6 +1362,9 @@ static int rproc_start(struct rproc *rproc, 
>>> const struct firmware *fw)
>>>        rproc_unprepare_subdevices(rproc);
>>>    reset_table_ptr:
>>>        rproc->table_ptr = rproc->cached_table;
>>>  +unprepare_rproc:
>>>  +    if (rproc->ops->unprepare)
>>>  +        rproc->ops->unprepare(rproc);
>>>
>>>        return ret;
>>>    }
>>>  @@ -1483,6 +1494,9 @@ static int rproc_stop(struct rproc *rproc, 
>>> bool crashed)
>>>
>>>        rproc->state = RPROC_OFFLINE;
>>>
>>>  +    if (rproc->ops->unprepare)
>>>  +        rproc->ops->unprepare(rproc);
>>>  +
>>>        dev_info(dev, "stopped remote processor %s\n", rproc->name);
>>>
>>>        return 0;
>>>  diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
>>>  index 5f201f0c86c3..a6272d1ba384 100644
>>>  --- a/include/linux/remoteproc.h
>>>  +++ b/include/linux/remoteproc.h
>>>  @@ -355,6 +355,8 @@ enum rsc_handling_status {
>>>
>>>    /**
>>>     * struct rproc_ops - platform-specific device handlers
>>>  + * @prepare:    prepare the device for power up (before the 
>>> firmware is loaded)
>>>  + * @unprepare:    unprepare the device after it is stopped
>>>     * @start:    power on the device and boot it
>>>     * @stop:    power off the device
>>>     * @kick:    kick a virtqueue (virtqueue id given as a parameter)
>>>  @@ -371,6 +373,8 @@ enum rsc_handling_status {
>>>     * @get_boot_addr:    get boot address to entry point specified 
>>> in firmware
>>>     */
>>>    struct rproc_ops {
>>>  +    int (*prepare)(struct rproc *rproc);
>>>  +    void (*unprepare)(struct rproc *rproc);
>>>        int (*start)(struct rproc *rproc);
>>>        int (*stop)(struct rproc *rproc);
>>>        void (*kick)(struct rproc *rproc, int vqid);
>
>