From: Lukasz Luba <lukasz.luba@arm.com>
To: Cristian Marussi <cristian.marussi@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Cc: sudeep.holla@arm.com, james.quinlan@broadcom.com,
Jonathan.Cameron@Huawei.com
Subject: Re: [PATCH v4 07/13] firmware: arm_scmi: Add notification dispatch and delivery
Date: Thu, 12 Mar 2020 20:57:28 +0000 [thread overview]
Message-ID: <cb4e38be-e8f7-483f-feda-94a19cad1ab1@arm.com> (raw)
In-Reply-To: <c9d64cad-3bde-602f-ab83-21c997fa472f@arm.com>
On 3/12/20 7:24 PM, Cristian Marussi wrote:
> On 12/03/2020 14:06, Lukasz Luba wrote:
>>
>>
>> On 3/12/20 1:51 PM, Lukasz Luba wrote:
>>> Hi Cristian,
>>>
>
> Hi Lukasz
>
>>> just one comment below...
>>>
>>> On 3/4/20 4:25 PM, Cristian Marussi wrote:
>>>> Add core SCMI Notifications dispatch and delivery support logic which is
>>>> able, at first, to dispatch well-known received events from the RX ISR to
>>>> the dedicated deferred worker, and then, from there, to final deliver the
>>>> events to the registered users' callbacks.
>>>>
>>>> Dispatch and delivery is just added here, still not enabled.
>>>>
>>>> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
>>>> ---
>>>> V3 --> V4
>>>> - dispatcher now handles dequeuing of events in chunks (header+payload):
>>>> handling of these in_flight events let us remove one unneeded memcpy
>>>> on RX interrupt path (scmi_notify)
>>>> - deferred dispatcher now access their own per-protocol handlers' table
>>>> reducing locking contention on the RX path
>>>> V2 --> V3
>>>> - exposing wq in sysfs via WQ_SYSFS
>>>> V1 --> V2
>>>> - splitted out of V1 patch 04
>>>> - moved from IDR maps to real HashTables to store event_handlers
>>>> - simplified delivery logic
>>>> ---
>>>> drivers/firmware/arm_scmi/notify.c | 334 ++++++++++++++++++++++++++++-
>>>> drivers/firmware/arm_scmi/notify.h | 9 +
>>>> 2 files changed, 342 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/firmware/arm_scmi/notify.c
>>>> b/drivers/firmware/arm_scmi/notify.c
>>>
>>> [snip]
>>>
>>>> +
>>>> +/**
>>>> + * scmi_notify - Queues a notification for further deferred processing
>>>> + *
>>>> + * This is called in interrupt context to queue a received event for
>>>> + * deferred processing.
>>>> + *
>>>> + * @handle: The handle identifying the platform instance from which the
>>>> + * dispatched event is generated
>>>> + * @proto_id: Protocol ID
>>>> + * @evt_id: Event ID (msgID)
>>>> + * @buf: Event Message Payload (without the header)
>>>> + * @len: Event Message Payload size
>>>> + * @ts: RX Timestamp in nanoseconds (boottime)
>>>> + *
>>>> + * Return: 0 on Success
>>>> + */
>>>> +int scmi_notify(const struct scmi_handle *handle, u8 proto_id, u8
>>>> evt_id,
>>>> + const void *buf, size_t len, u64 ts)
>>>> +{
>>>> + struct scmi_registered_event *r_evt;
>>>> + struct scmi_event_header eh;
>>>> + struct scmi_notify_instance *ni = handle->notify_priv;
>>>> +
>>>> + /* Ensure atomic value is updated */
>>>> + smp_mb__before_atomic();
>>>> + if (unlikely(!atomic_read(&ni->enabled)))
>>>> + return 0;
>>>> +
>>>> + r_evt = SCMI_GET_REVT(ni, proto_id, evt_id);
>>>> + if (unlikely(!r_evt))
>>>> + return -EINVAL;
>>>> +
>>>> + if (unlikely(len > r_evt->evt->max_payld_sz)) {
>>>> + pr_err("SCMI Notifications: discard badly sized message\n");
>>>> + return -EINVAL;
>>>> + }
>>>> + if (unlikely(kfifo_avail(&r_evt->proto->equeue.kfifo) <
>>>> + sizeof(eh) + len)) {
>>>> + pr_warn("SCMI Notifications: queue full dropping proto_id:%d
>>>> evt_id:%d ts:%lld\n",
>>>> + proto_id, evt_id, ts);
>>>> + return -ENOMEM;
>>>> + }
>>>> +
>>>> + eh.timestamp = ts;
>>>> + eh.evt_id = evt_id;
>>>> + eh.payld_sz = len;
>>>> + kfifo_in(&r_evt->proto->equeue.kfifo, &eh, sizeof(eh));
>>>> + kfifo_in(&r_evt->proto->equeue.kfifo, buf, len);
>>>> + queue_work(r_evt->proto->equeue.wq,
>>>> + &r_evt->proto->equeue.notify_work);
>>>
>>> Is it safe to ignore the return value from the queue_work here?
>>
>> and also from the kfifo_in
>>
>
> kfifo_in returns the number of effectively written bytes (using __kfifo_in),
> possibly capped to the effectively maximum available space in the fifo, BUT since I
> absolutely cannot afford to write an incomplete/truncated event into the queue, I check
> that in advance and backout on queue full:
>
> if (unlikely(kfifo_avail(&r_evt->proto->equeue.kfifo) < sizeof(eh) + len)) {
> return -ENOMEM;
>
> and given that the ISR scmi_notify() is the only possible writer on this queue
Yes, your are right, no other IRQ will show up for this channel till
we exit mailbox rx callback and clean the bits.
> I can be sure that the kfifo_in() will succeed in writing the required number of
> bytes after the above check...so I don't need to check the return value.
>
> Regards
>
> Cristian
>
>>>
>>> Regards,
>>> Lukasz
>>>
>>>
>
next prev parent reply other threads:[~2020-03-12 20:57 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-04 16:25 [PATCH v4 00/13] SCMI Notifications Core Support Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 01/13] firmware: arm_scmi: Add receive buffer support for notifications Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 02/13] firmware: arm_scmi: Update protocol commands and notification list Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 03/13] firmware: arm_scmi: Add notifications support in transport layer Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 04/13] firmware: arm_scmi: Add support for notifications message processing Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 05/13] firmware: arm_scmi: Add notification protocol-registration Cristian Marussi
2020-03-09 11:33 ` Jonathan Cameron
2020-03-09 12:04 ` Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 06/13] firmware: arm_scmi: Add notification callbacks-registration Cristian Marussi
2020-03-09 11:50 ` Jonathan Cameron
2020-03-09 12:25 ` Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 07/13] firmware: arm_scmi: Add notification dispatch and delivery Cristian Marussi
2020-03-09 12:26 ` Jonathan Cameron
2020-03-09 16:37 ` Cristian Marussi
2020-03-10 10:01 ` Jonathan Cameron
2020-03-12 13:51 ` Lukasz Luba
2020-03-12 14:06 ` Lukasz Luba
2020-03-12 19:24 ` Cristian Marussi
2020-03-12 20:57 ` Lukasz Luba [this message]
2020-03-12 18:34 ` Cristian Marussi
2020-03-12 21:43 ` Lukasz Luba
2020-03-16 14:46 ` Cristian Marussi
2020-03-18 8:26 ` Lukasz Luba
2020-03-23 8:28 ` Cristian Marussi
2020-05-20 7:09 ` Cristian Marussi
2020-05-20 10:23 ` Lukasz Luba
2020-03-04 16:25 ` [PATCH v4 08/13] firmware: arm_scmi: Enable notification core Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 09/13] firmware: arm_scmi: Add Power notifications support Cristian Marussi
2020-03-09 12:28 ` Jonathan Cameron
2020-03-09 16:39 ` Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 10/13] firmware: arm_scmi: Add Perf " Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 11/13] firmware: arm_scmi: Add Sensor " Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 12/13] firmware: arm_scmi: Add Reset " Cristian Marussi
2020-03-04 16:25 ` [PATCH v4 13/13] firmware: arm_scmi: Add Base " Cristian Marussi
2020-03-09 12:33 ` [PATCH v4 00/13] SCMI Notifications Core Support Jonathan Cameron
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