linux-kernel - Re: [PATCH] mfd: omap-usb-tll: check clk

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Message-ID: <20241119145622.2f1f0342@akair>
Date: Tue, 19 Nov 2024 14:56:22 +0100
From: Andreas Kemnade <andreas@...nade.info>
To: Roger Quadros <rogerq@...nel.org>
Cc: Karol Przybylski <karprzy7@...il.com>, aaro.koskinen@....fi,
 khilman@...libre.com, tony@...mide.com, lee@...nel.org,
 linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
 skhan@...uxfoundation.org
Subject: Re: [PATCH] mfd: omap-usb-tll: check clk_prepare return code

Am Tue, 19 Nov 2024 15:10:23 +0200
schrieb Roger Quadros <rogerq@...nel.org>:

> Hi,
> 
> On 13/11/2024 23:16, Karol Przybylski wrote:
> > clk_prepare() is called in usbtll_omap_probe to fill clk array.
> > Return code is not checked, leaving possible error condition unhandled.
> > 
> > Added variable to hold return value from clk_prepare() and dev_dbg statement
> > when it's not successful.
> > 
> > Found in coverity scan, CID 1594680
> > 
> > Signed-off-by: Karol Przybylski <karprzy7@...il.com>
> > ---
> >  drivers/mfd/omap-usb-tll.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/mfd/omap-usb-tll.c b/drivers/mfd/omap-usb-tll.c
> > index 0f7fdb99c809..2e9319ee1b74 100644
> > --- a/drivers/mfd/omap-usb-tll.c
> > +++ b/drivers/mfd/omap-usb-tll.c
> > @@ -202,7 +202,7 @@ static int usbtll_omap_probe(struct platform_device *pdev)
> >  	struct device				*dev =  &pdev->dev;
> >  	struct usbtll_omap			*tll;
> >  	void __iomem				*base;
> > -	int					i, nch, ver;
> > +	int					i, nch, ver, err;
> >  
> >  	dev_dbg(dev, "starting TI HSUSB TLL Controller\n");
> >  
> > @@ -248,10 +248,13 @@ static int usbtll_omap_probe(struct platform_device *pdev)
> >  					"usb_tll_hs_usb_ch%d_clk", i);
> >  		tll->ch_clk[i] = clk_get(dev, clkname);
> >  
> > -		if (IS_ERR(tll->ch_clk[i]))
> > +		if (IS_ERR(tll->ch_clk[i])) {
> >  			dev_dbg(dev, "can't get clock : %s\n", clkname);

if you want dev_err() later, then why not here?

> > -		else
> > -			clk_prepare(tll->ch_clk[i]);
> > +		} else {
> > +			err = clk_prepare(tll->ch_clk[i]);
> > +			if (err)
> > +				dev_dbg(dev, "clock prepare error for: %s\n", clkname);  
> 
> dev_err()?
> 
So why do you want a different return handling here? (I doubt there is
any clock having a real prepare() involved here)

As said in an earlier incarnation of this patch, the real question is
whether having partial clocks available is a valid operating scenario.
If yes, then the error should be ignored. If no, then bailing out early
is a good idea.

clk_prepare() errors are catched by failing clk_enable() later,
ch_clk[i] is checked later, too.

> I think we should return the error in this case.
> (after unpreparing the prepared clocks and clk_put())
>
and pm_runtime_put_sync(dev) 

Regards,
Andreas