linux-kernel - Re: RE: RE: [PATCH v3 1/2] can: m_can: Move mram init to mcan device setup

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Message-ID: <20221202150439.dmt7omdck7wdjpbv@pengutronix.de>
Date:   Fri, 2 Dec 2022 16:04:39 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Vivek Yadav <vivek.2311@...sung.com>
Cc:     rcsekar@...sung.com, krzysztof.kozlowski+dt@...aro.org,
        wg@...ndegger.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, pankaj.dubey@...sung.com,
        ravi.patel@...sung.com, alim.akhtar@...sung.com,
        linux-fsd@...la.com, robh+dt@...nel.org, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org,
        aswani.reddy@...sung.com, sriranjani.p@...sung.com
Subject: Re: RE: RE: [PATCH v3 1/2] can: m_can: Move mram init to mcan device
 setup

On 01.12.2022 09:40:50, Vivek Yadav wrote:
> > That probably depends on you power management. If I add a regulator
> > to power the external tcan4x5x chip and power it up during open(), I
> > need to initialize the RAM.
> > 
> Thanks for the clarification,
>
> There is one doubt for which I need clarity if I add ram init in
> m_can_chip_config.
> 
> In the current implementation, m_can_ram_init is added in the probe
> and m_can_class_resume function.
>
> If I add the ram init function in chip_config which is getting called
> from m_can_start, then m_can_init_ram will be called two times, once
> in resume and next from m_can_start also.

As m_can_start() is called from resume, remove the direct call to
m_can_init_ram() from m_can_class_resume().

> Can we add ram init inside the m_can_open function itself? Because it
> is independent of m_can resume functionality.

See above.

mainline implementation:

m_can_class_resume()
        -> m_can_init_ram()

m_can_open()
        -> m_can_start()
        -> m_can_chip_config()
        -> ops->init
                m_can_init_ram() (for tcan only)


proposed:

m_can_class_resume()
        -> m_can_start()
        -> m_can_chip_config()
        -> m_can_init_ram()

m_can_open()
        -> m_can_start()
        -> m_can_chip_config()
        -> m_can_init_ram()

In mainline m_can_init_ram() is called for the tcan during open(). So if
you call m_can_init_ram() from m_can_chip_config(), remove it from the
tcan's tcan4x5x_init() functions, and from m_can_class_resume() it
should only be called once for open and once for resume.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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