linux-kernel - RE: [PATCH 2/2] i2c: designware: Add support for a bus clock

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Message-ID: <TY1PR01MB1769F130075F1635CC51532FF55C0@TY1PR01MB1769.jpnprd01.prod.outlook.com>
Date:   Tue, 17 Jul 2018 14:40:03 +0000
From:   Phil Edworthy <phil.edworthy@...esas.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Simon Horman <horms@...ge.net.au>
CC:     Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: RE: [PATCH 2/2] i2c: designware: Add support for a bus clock

Hi Andy,

On 17 July 2018 15:19, Andy Shevchenko wrote:
> On Tue, 2018-07-17 at 12:42 +0000, Phil Edworthy wrote:
> 
> > > While your point sounds valid (don't remember how clk_get() is
> > > implemented), NULL is also OK to have.
> >
> > Ok as in there is no bus clock, right?
> > So it should be:
> >  if (!IS_ERR_OR_NULL (dev->busclk))
> 
> Nope, NULL is no error case for optional clock.
I must be missing something here...
I agree that NULL for an optional clock is not an error. However, the 
code above is now:
+	if (prepare) {
+		/* Optional bus clock */
+		if (!IS_ERR_OR_NULL(dev->busclk)) {
+			ret = clk_prepare_enable(dev->busclk);
+			if (ret)
+				return ret;
+		}
+
 		return clk_prepare_enable(dev->clk);
+	}

So, if you have a valid busclk, it gets enabled, otherwise it is
left alone.

Thanks
Phil