linux-kernel - Re: [PATCH 1/2] soc: imx-sc: add i.MX system controller soc driver support

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Date:   Fri, 10 May 2019 10:42:17 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Leonard Crestez <leonard.crestez@....com>
Cc:     Anson Huang <anson.huang@....com>,
        "stefan.wahren@...e.com" <stefan.wahren@...e.com>,
        "enric.balletbo@...labora.com" <enric.balletbo@...labora.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "heiko@...ech.de" <heiko@...ech.de>,
        "marc.w.gonzalez@...e.fr" <marc.w.gonzalez@...e.fr>,
        "ezequiel@...labora.com" <ezequiel@...labora.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "will.deacon@....com" <will.deacon@....com>,
        Abel Vesa <abel.vesa@....com>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        Andy Gross <andy.gross@...aro.org>,
        "jagan@...rulasolutions.com" <jagan@...rulasolutions.com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        "olof@...om.net" <olof@...om.net>,
        "horms+renesas@...ge.net.au" <horms+renesas@...ge.net.au>,
        "festevam@...il.com" <festevam@...il.com>,
        "robh@...nel.org" <robh@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>
Subject: Re: [PATCH 1/2] soc: imx-sc: add i.MX system controller soc driver
 support

On Mon, Apr 22, 2019 at 08:48:56AM +0000, Leonard Crestez wrote:
> On 4/22/2019 9:46 AM, Anson Huang wrote:
> >> -----Original Message-----
> >> From: Anson Huang
> >>> From: Shawn Guo [mailto:shawnguo@...nel.org]
> >>> On Sun, Apr 21, 2019 at 03:40:00PM +0800, Shawn Guo wrote:
> >>>> On Thu, Apr 11, 2019 at 06:49:12AM +0000, Anson Huang wrote:
> >>>>> i.MX8QXP is an ARMv8 SoC which has a Cortex-M4 system controller
> >>>>> inside, the system controller is in charge of controlling power,
> >>>>> clock and fuse etc..
> >>>>>
> >>>>> This patch adds i.MX system controller soc driver support, Linux
> >>>>> kernel has to communicate with system controller via MU (message
> >>>>> unit) IPC to get soc revision, uid etc..
> >>>>>
> >>>>> With this patch, soc info can be read from sysfs:
> >>>>>
> >>>>>   drivers/soc/imx/Kconfig      |   7 ++
> >>>>>   drivers/soc/imx/Makefile     |   1 +
> >>>>>   drivers/soc/imx/soc-imx-sc.c | 220
> >>>>> +++++++++++++++++++++++++++++++++++++++++++
> >>>>>   3 files changed, 228 insertions(+)  create mode 100644
> >>>>> drivers/soc/imx/soc-imx-sc.c
> >>>>
> >>>> Rather than creating a new driver, please take a look at Abel's
> >>>> generic
> >>>> i.MX8 SoC driver, and see if it can be extended to cover i.MX8QXP.
> >>
> >> Got it, I didn't notice that this patch bas been accepted, I will redo the patch
> >> based on it, thanks.
> > 
> > I have sent the new patch set to support i.MX8QXP SoC revision based on generic i.MX8
> > SoC driver, however, the Kconfig modification is NOT good, it may break i.MX8MQ if IMX_SCU
> > is NOT enabled, although we can add some warp function for SCU firmware API call to fix it,
> > but after further thought and discussion with Dong Aisheng, I think we may need to roll back to
> > use this patch series to create a new SoC driver dedicated for i.MX8 SoCs
> > with system controller inside, such as i.MX8QXP, i.MX8QM etc., the reason are as below:
> > 
> > For i.MX8MQ/i.MX8MM:
> > 	1. SoC driver does NOT depends on i.MX SCU firmware, so no need to use platform driver
> > 	     probe model, just device_init phase call is good enough;
> > 	2. The SoC driver no need to depends on IMX_SCU, so it can be always built in, no need to
> > 	     check IMX_SCU config;
> > 	3. The fuse check for CPU speed grading, HDCP status, NoC settings etc. could be added to this driver,
> > 	    but they are ONLY for i.MX8MQ/i.MX8MM etc..
> > For i.MX8QXP/i.MX8QM:
> > 	1. SoC driver MUST depends on IMX_SCU;
> > 	2. MUST use platform model to support defer probe;
> > 	3. No fuse check for CPU speed grading.
> > 
> > So, I guess the reused code for i.MX8MQ and i.MX8QXP is ONLY those part of creating SoC id device node (less than
> > 30% I think), all other functions are implemented in total different ways, that is why I created the imx_sc_soc driver
> > in this patch series, so do you think we can add new SoC driver for i.MX8 SoC with SCU inside? Putting 2 different architecture
> > SoCs' driver into 1 file looks like NOT making enough sense.
> 
> +1 for separate SOC driver. The 8mq/8mm and 8qm/8qxp families are very 
> different, they just happen to share the imx8 prefix.
> 
> It makes sense to allow people to compile one without the other and this 
> is easier with distinct SOC drivers.

Leonard, Abel,

Can you guys help review the patch?  Thanks.

Shawn