linux-kernel - RE: [PATCH v6 09/11] firmware: xilinx: Add debugfs for clock control APIs

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Date:   Mon, 14 May 2018 19:18:44 +0000
From:   Jolly Shah <JOLLYS@...inx.com>
To:     Sudeep Holla <sudeep.holla@....com>,
        "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...eaurora.org" <sboyd@...eaurora.org>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>
CC:     Rajan Vaja <RAJANV@...inx.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH v6 09/11] firmware: xilinx: Add debugfs for clock control
 APIs

Hi Sudeep,

> -----Original Message-----
> From: Sudeep Holla [mailto:sudeep.holla@....com]
> Sent: Thursday, May 10, 2018 7:31 AM
> To: Jolly Shah <JOLLYS@...inx.com>; ard.biesheuvel@...aro.org;
> mingo@...nel.org; gregkh@...uxfoundation.org; matt@...eblueprint.co.uk;
> hkallweit1@...il.com; keescook@...omium.org;
> dmitry.torokhov@...il.com; mturquette@...libre.com;
> sboyd@...eaurora.org; michal.simek@...inx.com; robh+dt@...nel.org;
> mark.rutland@....com; linux-clk@...r.kernel.org
> Cc: Sudeep Holla <sudeep.holla@....com>; Rajan Vaja <RAJANV@...inx.com>;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> devicetree@...r.kernel.org; Jolly Shah <JOLLYS@...inx.com>
> Subject: Re: [PATCH v6 09/11] firmware: xilinx: Add debugfs for clock control
> APIs
> 
> 
> 
> On 10/04/18 20:38, Jolly Shah wrote:
> > From: Rajan Vaja <rajanv@...inx.com>
> >
> > Add debugfs file to control clocks using firmware APIs through debugfs
> > interface.
> >
> > Signed-off-by: Rajan Vaja <rajanv@...inx.com>
> > Signed-off-by: Jolly Shah <jollys@...inx.com>
> > ---
> >  drivers/firmware/xilinx/zynqmp-debug.c | 48
> > ++++++++++++++++++++++++++++++++++
> >  1 file changed, 48 insertions(+)
> >
> > diff --git a/drivers/firmware/xilinx/zynqmp-debug.c
> > b/drivers/firmware/xilinx/zynqmp-debug.c
> > index 1cb69f7..837fcd1 100644
> > --- a/drivers/firmware/xilinx/zynqmp-debug.c
> > +++ b/drivers/firmware/xilinx/zynqmp-debug.c
> > @@ -34,6 +34,15 @@ static struct pm_api_info pm_api_list[] = {
> >  	PM_API(PM_GET_API_VERSION),
> >  	PM_API(PM_IOCTL),
> >  	PM_API(PM_QUERY_DATA),
> > +	PM_API(PM_CLOCK_ENABLE),
> > +	PM_API(PM_CLOCK_DISABLE),
> > +	PM_API(PM_CLOCK_GETSTATE),
> > +	PM_API(PM_CLOCK_SETDIVIDER),
> > +	PM_API(PM_CLOCK_GETDIVIDER),
> > +	PM_API(PM_CLOCK_SETRATE),
> > +	PM_API(PM_CLOCK_GETRATE),
> > +	PM_API(PM_CLOCK_SETPARENT),
> > +	PM_API(PM_CLOCK_GETPARENT),
> >  };
> >
> >  /**
> > @@ -87,6 +96,7 @@ static int process_api_request(u32 pm_id, u64
> *pm_api_arg, u32 *pm_api_ret)
> >  	const struct zynqmp_eemi_ops *eemi_ops =
> zynqmp_pm_get_eemi_ops();
> >  	u32 pm_api_version;
> >  	int ret;
> > +	u64 rate;
> >
> >  	if (!eemi_ops)
> >  		return -ENXIO;
> > @@ -132,6 +142,44 @@ static int process_api_request(u32 pm_id, u64
> *pm_api_arg, u32 *pm_api_ret)
> >  				pm_api_ret[2], pm_api_ret[3]);
> >  		break;
> >  	}
> > +	case PM_CLOCK_ENABLE:
> > +		ret = eemi_ops->clock_enable(pm_api_arg[0]);
> > +		break;
> 
> As I mentioned in earlier patch, I don't see the need for this debugfs interface.
> Clock lay has read-only interface in debugfs already. Also if you want to debug
> clocks, you can do so using the driver which uses these clocks. Do you really
> want to manage clocks in user-space ?
> The whole idea of EEMI kind of interface is to abstract and hide the fine details
> even from non-trusted rich OS like Linux kernel, but by providing this you are
> doing exactly opposite.
> 
> --
> Regards,
> Sudeep

No we don't want to manage clocks in user-space. This debugfs is meant for developer who wants to debug APIs behavior in case something doesn't work as expected. Debugfs should be off by default in production images.

Thanks,
Jolly Shah