Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752772AbdGYQHf (ORCPT ); Tue, 25 Jul 2017 12:07:35 -0400 Received: from mail-wm0-f42.google.com ([74.125.82.42]:35089 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752226AbdGYQHd (ORCPT ); Tue, 25 Jul 2017 12:07:33 -0400 MIME-Version: 1.0 In-Reply-To: References: <1500620142-910-1-git-send-email-anup.patel@broadcom.com> <1500620142-910-7-git-send-email-anup.patel@broadcom.com> From: Jassi Brar Date: Tue, 25 Jul 2017 21:37:31 +0530 Message-ID: Subject: Re: [PATCH v2 6/7] mailbox: bcm-flexrm-mailbox: Set msg_queue_len for each channel To: Anup Patel Cc: Rob Herring , Mark Rutland , Catalin Marinas , Will Deacon , Florian Fainelli , Scott Branden , Ray Jui , Linux Kernel Mailing List , "linux-arm-kernel@lists.infradead.org" , Devicetree List , BCM Kernel Feedback Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3918 Lines: 85 On Tue, Jul 25, 2017 at 11:11 AM, Anup Patel wrote: > On Mon, Jul 24, 2017 at 10:06 PM, Jassi Brar wrote: >> On Mon, Jul 24, 2017 at 9:26 AM, Anup Patel wrote: >>> Hi Jassi, >>> >>> Sorry for the delayed response... >>> >>> On Fri, Jul 21, 2017 at 9:16 PM, Jassi Brar wrote: >>>> Hi Anup, >>>> >>>> On Fri, Jul 21, 2017 at 12:25 PM, Anup Patel wrote: >>>>> The Broadcom FlexRM ring (i.e. mailbox channel) can handle >>>>> larger number of messages queued in one FlexRM ring hence >>>>> this patch sets msg_queue_len for each mailbox channel to >>>>> be same as RING_MAX_REQ_COUNT. >>>>> >>>>> Signed-off-by: Anup Patel >>>>> Reviewed-by: Scott Branden >>>>> --- >>>>> drivers/mailbox/bcm-flexrm-mailbox.c | 5 ++++- >>>>> 1 file changed, 4 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/mailbox/bcm-flexrm-mailbox.c b/drivers/mailbox/bcm-flexrm-mailbox.c >>>>> index 9873818..20055a0 100644 >>>>> --- a/drivers/mailbox/bcm-flexrm-mailbox.c >>>>> +++ b/drivers/mailbox/bcm-flexrm-mailbox.c >>>>> @@ -1683,8 +1683,11 @@ static int flexrm_mbox_probe(struct platform_device *pdev) >>>>> ret = -ENOMEM; >>>>> goto fail_free_debugfs_root; >>>>> } >>>>> - for (index = 0; index < mbox->num_rings; index++) >>>>> + for (index = 0; index < mbox->num_rings; index++) { >>>>> + mbox->controller.chans[index].msg_queue_len = >>>>> + RING_MAX_REQ_COUNT; >>>>> mbox->controller.chans[index].con_priv = &mbox->rings[index]; >>>>> + } >>>>> >>>> While writing mailbox.c I wasn't unaware that there is the option to >>>> choose the queue length at runtime. >>>> The idea was to keep the code as simple as possible. I am open to >>>> making it a runtime thing, but first, please help me understand how >>>> that is useful here. >>>> >>>> I understand FlexRm has a ring buffer of RING_MAX_REQ_COUNT(1024) >>>> elements. Any message submitted to mailbox api can be immediately >>>> written onto the ringbuffer if there is some space. >>>> Is there any mechanism to report back to a client driver, if its >>>> message in ringbuffer failed "to be sent"? >>>> If there isn't any, then I think, in flexrm_last_tx_done() you should >>>> simply return true if there is some space left in the rung-buffer, >>>> false otherwise. >>> >>> Yes, we have error code in "struct brcm_message" to report back >>> errors from send_message. In our mailbox clients, we check >>> return value of mbox_send_message() and also the error code >>> in "struct brcm_message". >>> >> I meant after the message has been accepted in the ringbuffer but the >> remote failed to receive it. > > Yes, even this case is handled. > > In case of IO errors after message has been put in ring buffer, we get > completion message with error code and mailbox client drivers will > receive back "struct brcm_message" with error set. > > You can refer flexrm_process_completions() for more details. > >> There seems no such provision. IIANW, then you should be able to >> consider every message as "sent successfully" once it is in the ring >> buffer i.e, immediately after mbox_send_message() returns 0. >> In that case I would think you don't need more than a couple of >> entries out of MBOX_TX_QUEUE_LEN ? > > What I am trying to suggest is that we can take upto 1024 messages > in a FlexRM ring but the MBOX_TX_QUEUE_LEN limits us queuing > more messages. This issue manifest easily when multiple CPUs > queues to same FlexRM ring (i.e. same mailbox channel). > OK then, I guess we have to make the queue length a runtime decision. BTW, is it a practical use case that needs to queue upto 1024 requests? Or are you just testing? Thanks