linux-kernel - Re: [PATCH 2/3] Input: snvs_pwrkey

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Message-ID: <7c3a08e97281a54105225fa4f212f5279d3fac30.camel@andred.net>
Date:   Tue, 11 Feb 2020 09:13:33 +0000
From:   André Draszik <git@...red.net>
To:     Robin Gong <yibin.gong@....com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Horia Geanta <horia.geanta@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Anson Huang <anson.huang@....com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH 2/3] Input: snvs_pwrkey - enable snvs clock as needed

Hi,

On Tue, 2020-02-11 at 01:54 +0000, Robin Gong wrote:
> On 2020/02/11 Dmitry Torokhov <dmitry.torokhov@...il.com> wrote: 
> > On Mon, Feb 10, 2020 at 06:33:30AM +0000, Horia Geanta wrote:
> > > On 2/10/2020 4:03 AM, Robin Gong wrote:
> > > > On 2020/02/10 Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> > > > > On Fri, Feb 07, 2020 at 08:10:22AM +0000, Horia Geanta wrote:
> > > > > > On 1/30/2020 10:45 PM, André Draszik wrote:
> > > > > > > @@ -140,6 +148,25 @@ static int imx_snvs_pwrkey_probe(struct
> > > > > platform_device *pdev)
> > > > > > >  	if (pdata->irq < 0)
> > > > > > >  		return -EINVAL;
> > > > > > > 
> > > > > > > +	pdata->clk = devm_clk_get(&pdev->dev, "snvs-pwrkey");
> > > > > > > +	if (IS_ERR(pdata->clk)) {
> > > > > > > +		pdata->clk = NULL;
> > > > > > Using devm_clk_get_optional() would simplify error handling.
> > > > > 
> > > > > It sounds to me that this clock is not at all optional and the
> > > > > driver currently "works" only by accident and therefore optional is not
> > suitable here.
> > > > Yes, then we need to add all snvs clk in dts for on legacy i.MX
> > > > chips in this patchset to avoid any potential function broken.
> > 
> > How many are there? I am not too terribly opposed of having the driver handle
> > missing clk if there are very many legacy DTSes out there. But then we need to
> > handle it properly (i.e. current iteration does not handle referral properly for
> > example).
> There are four dtsi which have clock support in snvs-rtc  including i.mx7s/i.mx8mq/8mm/8mn. So for this patch set,
> it's better update
> i.mx8mX dtsi except i.mx7s.
> > > In that case the DT binding should be updated too, to make the clock
> > > mandatory.
> > 
> > I think this should be done in either case, as as far I understand the part can not
> > function without the clock and it worked purely by chance on some systems as
> > something else was turning the clock on.
> Yes, for all chips snvs clk management added, snvs clock also has to been add
> in snvs_pwrkey dts, but for others legacy chips like i.mx6X which have no snvs
> clk management, snvs clock is always on, so no need such clk in snvs_pwrkey
> dts either, optional is better.
> > Thanks.

It seems to me though that the clock should really be moved into the (parent) SNVS
node itself, rather than duplicating
the clock in the the power key node and in
the RTC node. Is that possible? (I don't know)...

To summarise, I'll post an updated patchset within the next couple days so to:

* keep the clock optional (for i.MX6 platforms)
* convert to devm_clk_get_optional()
* only enable the clock in interrupt handler and imx_imx_snvs_check_for_events()
  but not during driver loading
* update all four DTSIs: imx8mm.dtsi imx8mn.dtsi imx8mq.dtsi imx7s.dtsi
  Note that I'll only be able to test onn the i.MX7


Cheers,
Andre'