linux-kernel - RE: [PATCH v4 2/2] misc: Add iop driver for Sunplus SP7021

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Date:   Mon, 20 Dec 2021 08:35:15 +0000
From:   Tony Huang 黃懷厚 <tony.huang@...plus.com>
To:     gregkh <gregkh@...uxfoundation.org>
CC:     Wells Lu 呂芳騰 <wells.lu@...plus.com>,
        Rob Herring <robh+dt@...nel.org>,
        DTML <devicetree@...r.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Derek Kiernan <derek.kiernan@...inx.com>,
        Dragan Cvetic <dragan.cvetic@...inx.com>,
        "Arnd Bergmann" <arnd@...db.de>,
        黃懷厚 <tonyhuang.sunplus@...il.com>
Subject: RE: [PATCH v4 2/2] misc: Add iop driver for Sunplus SP7021

Dear grepkh:

> > > > +
> > > > +static ssize_t sp_iop_state1_show(struct device *dev, struct
> > > > +device_attribute *attr, char *buf) {
> > > > +     struct sp_iop *iop = dev_get_drvdata(dev);
> > > > +     ssize_t len = 0;
> > > > +
> > > > +     sp_iop_standby_mode(iop);
> > > > +     mdelay(10);
> > > > +     sp_iop_s1mode(dev, iop);
> > > > +     return len;
> > > > +}
> > >
> > > This function is not showing anything.
> > >
> >
> > The purpose of this function:
> > SP7021 has three power states:S0, S1 and S3.
> > S0:Default domain is on. IOP domain is on. AO domain is on.
> 
> > S1:Default domain is off. IOP domain is on. AO domain is on.
> 
> > S3:Default domain is off. IOP domain is off. AO domain is on.
> 
> > System enter S1 mode when read sysfs sp_iop_state1,
> 
> 
> That is not what sysfs is for, sorry.

I will modify this function.

> 
> > I hope to provide users with the ability to enter S1 mode by themselves.
> 
> > So I cannot use DEVICE_ATTR. I should use file_operations method.
> 
> 
> No, please use the normal power management callbacks for your driver that
> all other drivers use in the kernel.  There is nothing special about this one
> driver to warrant a totally new user/kernel api for it.
> 

OK, I understand.

Thanks