linux-kernel - Re: [PATCH v7 5/9] misc: smpro-misc: Add Ampere's Altra SMpro misc driver

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Message-ID: <YjhNP+Jzn/z4+5Zw@kroah.com>
Date:   Mon, 21 Mar 2022 11:02:39 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Quan Nguyen <quan@...amperecomputing.com>
Cc:     Lee Jones <lee.jones@...aro.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Jonathan Corbet <corbet@....net>,
        Derek Kiernan <derek.kiernan@...inx.com>,
        Dragan Cvetic <dragan.cvetic@...inx.com>,
        Arnd Bergmann <arnd@...db.de>,
        Thu Nguyen <thu@...amperecomputing.com>,
        Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:HARDWARE MONITORING" <linux-hwmon@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Open Source Submission <patches@...erecomputing.com>,
        Phong Vo <phong@...amperecomputing.com>,
        "Thang Q . Nguyen" <thang@...amperecomputing.com>
Subject: Re: [PATCH v7 5/9] misc: smpro-misc: Add Ampere's Altra SMpro misc
 driver

On Mon, Mar 21, 2022 at 04:46:50PM +0700, Quan Nguyen wrote:
> 
> 
> On 21/03/2022 15:21, Greg Kroah-Hartman wrote:
> > On Mon, Mar 21, 2022 at 03:13:51PM +0700, Quan Nguyen wrote:
> > > This commit adds driver support for accessing various information
> > > reported by Ampere's SMpro co-processor such as Boot Progress and
> > > other miscellaneous data.
> > > 
> > > Signed-off-by: Quan Nguyen <quan@...amperecomputing.com>
> > 
> > No Documentation/ABI/ entries for your sysfs file?
> > 
> 
> Thank you, Greg, for a very quick review.
> I have put this file in other patch.
> 
> > > +static ssize_t boot_progress_show(struct device *dev, struct device_attribute *da, char *buf)
> > > +{
> > > +	struct smpro_misc *misc = dev_get_drvdata(dev);
> > > +	u32 boot_progress;
> > > +	u8 current_stage;
> > > +	u8 boot_status;
> > > +	u8 boot_stage;
> > > +	u32 select;
> > > +	u32 reg_lo;
> > > +	u32 reg;
> > > +	int ret;
> > > +
> > > +	/* Read current boot stage */
> > > +	ret = regmap_read(misc->regmap, BOOTSTAGE_CUR_STAGE, &reg);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	current_stage = reg & 0xff;
> > > +
> > > +	/* Read the boot progress */
> > > +	ret = regmap_read(misc->regmap, BOOTSTAGE_SELECT, &select);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	boot_stage = (select >> 8) & 0xff;
> > > +	boot_status = select & 0xff;
> > > +
> > > +	if (boot_stage > current_stage)
> > > +		return -EINVAL;
> > > +
> > > +	ret = regmap_read(misc->regmap,	BOOTSTAGE_STATUS_LO, &reg_lo);
> > > +	if (!ret)
> > > +		ret = regmap_read(misc->regmap, BOOTSTAGE_STATUS_HI, &reg);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	boot_progress = swab16(reg) << 16 | swab16(reg_lo);
> > > +
> > > +	/* Tell firmware to provide next boot stage next time */
> > > +	if (boot_stage < current_stage) {
> > > +		ret = regmap_write(misc->regmap, BOOTSTAGE_SELECT, ((select & 0xff00) | 0x1));
> > > +		if (ret)
> > > +			return ret;
> > > +	}
> > > +
> > > +	return snprintf(buf, PAGE_SIZE, "0x%02x 0x%02x 0x%08x\n",
> > > +			boot_stage, boot_status, boot_progress);
> > 
> > sysfs_emit() please.
> > 
> Thanks, Greg.
> 
> Will switch to sysfs_emit() in my next version.
> 
> > Also, this is 3 different things, put all of these in different sysfs
> > files.
> > 
> > thanks,
> > 
> > greg k-h
> 
> Actually, no. It is single value of boot stage.

You are displaying 3 things in a single line, those are 3 different
things.

> Let me explain:
> The boot progress consists of three things together: boot_stage, boot_status
> and boot_progress and they have no meaning if reported them as three
> separate values:
> + boot_stage is to indicate the boot stage
> + boot_status is to report the result of that boot_stage: started, complete
> or error.
> + boot_progress is to report more extra information for the stage other than
> the boot_stage/boot_status.

Why are these just not 3 different files?  They describe three different
things, please do not EVER force userspace to parse a sysfs file other
than a single value.

thanks,

greg k-h