netdev - Re: [PATCH v5 2/2] can: m_can: Add hrtimer to generate software interrupt

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Date: Fri, 12 May 2023 15:26:10 -0500
From: Judith Mendez <jm@...com>
To: Tony Lindgren <tony@...mide.com>
CC: <linux-can@...r.kernel.org>,
        Chandrasekar Ramakrishnan
	<rcsekar@...sung.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc
 Kleine-Budde <mkl@...gutronix.de>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo
 Abeni <pabeni@...hat.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Schuyler Patton <spatton@...com>,
        <devicetree@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5 2/2] can: m_can: Add hrtimer to generate software
 interrupt

Hello Tony,

On 5/11/23 01:23, Tony Lindgren wrote:
> Hi,
> 
> * Judith Mendez <jm@...com> [230510 20:31]:
>> Add an hrtimer to MCAN class device. Each MCAN will have its own
>> hrtimer instantiated if there is no hardware interrupt found and
>> poll-interval property is defined in device tree M_CAN node.
>>
>> The hrtimer will generate a software interrupt every 1 ms. In
>> hrtimer callback, we check if there is a transaction pending by
>> reading a register, then process by calling the isr if there is.
> 
> So what about system suspend, do you need to do something to
> ensure the timer does not happen to run while suspending?

Great question. Tested the MCAN using timer polling method and

it seems to suspend to RAM but not resume. Meanwhile MCAN using

hardware irq suspends and resumes from RAM just fine. Will look

deeper into this here soon. Thank you Tony for bringing this up.



regards,

Judith