linux-kernel - Re: [PATCH v2 1/2] can: mcp251xfd: Try to get crystal clock rate from property

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Message-ID: <YLS0XwpFme+LFBAx@smile.fi.intel.com>
Date:   Mon, 31 May 2021 13:03:11 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Manivannan Sadhasivam <mani@...nel.org>,
        Thomas Kopp <thomas.kopp@...rochip.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH v2 1/2] can: mcp251xfd: Try to get crystal clock rate
 from property

On Mon, May 31, 2021 at 12:58:29PM +0300, Andy Shevchenko wrote:
> On Mon, May 31, 2021 at 10:47:20AM +0200, Marc Kleine-Budde wrote:
> > On 26.05.2021 22:33:26, Andy Shevchenko wrote:
> > > In some configurations, mainly ACPI-based, the clock frequency of the device
> > > is supplied by very well established 'clock-frequency' property. Hence, try
> > > to get it from the property at last if no other providers are available.
> 
> > >  		return dev_err_probe(&spi->dev, PTR_ERR(reg_xceiver),
> > >  				     "Failed to get Transceiver regulator!\n");
> > >  
> > > -	clk = devm_clk_get(&spi->dev, NULL);
> > > +	/* Always ask for fixed clock rate from a property. */
> > > +	device_property_read_u32(&spi->dev, "clock-frequency", &rate);
> > 
> > what about error handling....?
> 
> Not needed, but rate should be assigned to 0, which is missed.
> 
> > > +	clk = devm_clk_get_optional(&spi->dev, NULL);
> > >  	if (IS_ERR(clk))
> > >  		return dev_err_probe(&spi->dev, PTR_ERR(clk),
> > >  				     "Failed to get Oscillator (clock)!\n");
> > >  	freq = clk_get_rate(clk);
> > > +	if (freq == 0)
> > > +		freq = rate;
> > 
> > ... this means we don't fail if there is neither a clk nor a
> > clock-frequency property.
> 
> The following will check for it (which is already in the code)
> 
>   if (freq <= MCP251XFD_SYSCLOCK_HZ_MAX / MCP251XFD_OSC_PLL_MULTIPLIER) {

Even before, actually,

             /* Sanity check */
             if (freq < MCP251XFD_SYSCLOCK_HZ_MIN ||
		 freq > MCP251XFD_SYSCLOCK_HZ_MAX) {


> > I've send a v3 to fix this.
> 
> You mean I have to send v3?
> Sure!

So, I am going to send a v3 with amended commit message and assigning rate
to 0.

-- 
With Best Regards,
Andy Shevchenko