Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   "Vivek Yadav" <vivek.2311@samsung.com>
To:     "'Marc Kleine-Budde'" <mkl@pengutronix.de>
Cc:     <rcsekar@samsung.com>, <krzysztof.kozlowski+dt@linaro.org>,
        <wg@grandegger.com>, <davem@davemloft.net>, <edumazet@google.com>,
        <kuba@kernel.org>, <pabeni@redhat.com>, <pankaj.dubey@samsung.com>,
        <ravi.patel@samsung.com>, <alim.akhtar@samsung.com>,
        <linux-fsd@tesla.com>, <robh+dt@kernel.org>,
        <linux-can@vger.kernel.org>, <netdev@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-samsung-soc@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <aswani.reddy@samsung.com>, <sriranjani.p@samsung.com>
In-Reply-To: <20221124145405.d67cb6xmoiqfdsq3@pengutronix.de>
Subject: RE: RE: [PATCH v3 1/2] can: m_can: Move mram init to mcan device
 setup
Date:   Thu, 1 Dec 2022 09:40:50 +0530
Message-ID: <01f901d9053a$f138bdd0$d3aa3970$@samsung.com>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Thread-Index: AQKzKt4C0V6WIa1X2lvfORr5q2BWDgH5Y+bNAeiPnOMDLJn5dwD4TowRAqfPl+usTqoaEA==
Content-Language: en-in
Content-Type: text/plain; charset="utf-8"
CMS-TYPE: 105P
DLP-Filter: Pass
References: <20221122105455.39294-1-vivek.2311@samsung.com>
        <CGME20221122105022epcas5p3f5db1c5790b605bac8d319fe06ad915b@epcas5p3.samsung.com>
        <20221122105455.39294-2-vivek.2311@samsung.com>
        <20221123224146.iic52cuhhnwqk2te@pengutronix.de>
        <01a101d8ffe4$1797f290$46c7d7b0$@samsung.com>
        <20221124145405.d67cb6xmoiqfdsq3@pengutronix.de>
Precedence: bulk


> -----Original Message-----
> From: Marc Kleine-Budde <mkl=40pengutronix.de>
> Sent: 24 November 2022 20:24
> To: Vivek Yadav <vivek.2311=40samsung.com>
> Cc: rcsekar=40samsung.com; krzysztof.kozlowski+dt=40linaro.org;
> wg=40grandegger.com; davem=40davemloft.net; edumazet=40google.com;
> kuba=40kernel.org; pabeni=40redhat.com; pankaj.dubey=40samsung.com;
> ravi.patel=40samsung.com; alim.akhtar=40samsung.com; linux-fsd=40tesla.co=
m;
> robh+dt=40kernel.org; linux-can=40vger.kernel.org; netdev=40vger.kernel.o=
rg;
> linux-kernel=40vger.kernel.org; linux-arm-kernel=40lists.infradead.org; l=
inux-
> samsung-soc=40vger.kernel.org; devicetree=40vger.kernel.org;
> aswani.reddy=40samsung.com; sriranjani.p=40samsung.com
> Subject: Re: RE: =5BPATCH v3 1/2=5D can: m_can: Move mram init to mcan de=
vice
> setup
>=20
> On 24.11.2022 14:36:48, Vivek Yadav wrote:
> > > Why not call the RAM init directly from m_can_chip_config()?
> > >
> > m_can_chip_config function is called from m_can open.
> >
> > Configuring RAM init every time we open the CAN instance is not
> > needed, I think only once during the probe is enough.
>=20
> 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.
>=20
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_c=
an_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 a=
nd next from m_can_start also.

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

> > If message RAM init failed then fifo Transmit and receive will fail
> > and there will be no communication. So there is no point to =22open and
> > Configure CAN chip=22.
>=20
> For mmio devices the RAM init will probably not fail. There are return va=
lues
> and error checking for the SPI attached devices. Where the SPI
> communication will fail. However if this is problem, I assume the chip wi=
ll not
> be detected in the first place.
>=20
> > From my understanding it's better to keep RAM init inside the probe
> > and if there is a failure happened goes to CAN probe failure.
>=20
> Marc
>=20
> --
> Pengutronix e.K.                 =7C Marc Kleine-Budde           =7C
> Embedded Linux                   =7C
> https://protect2.fireeye.com/v1/url?k=3D2053d9ab-7fc8e0b4-205252e4-
> 000babdfecba-a8c309c53e3358f5&q=3D1&e=3Dc0cfd0e2-a422-4821-a49d-
> 113cfa4da9cb&u=3Dhttps%3A%2F%2Fwww.pengutronix.de%2F  =7C
> Vertretung West/Dortmund         =7C Phone: +49-231-2826-924     =7C
> Amtsgericht Hildesheim, HRA 2686 =7C Fax:   +49-5121-206917-5555 =7C