[PATCH] mtd: nand: orion: fix clk handling

[Simon Baatz]

On Thu, Mar 16, 2017 at 10:12:11AM +0100, Boris Brezillon wrote:
> On Mon, 13 Mar 2017 08:12:41 +0100
> Uwe Kleine-König <u.kleine-koenig at pengutronix.de> wrote:
> 
> > Hello Simon,
> > 
> > On Sun, Mar 12, 2017 at 10:34:06PM +0100, Simon Baatz wrote:
> > > The clk handling in orion_nand.c had two problems:
> > > 
> > > - In the probe function, clk_put() was called for an enabled clock,
> > >   which violates the API (see documentation for clk_put() in
> > >   include/linux/clk.h)
> > > 
> > > - In the error path of the probe function, clk_put() could be called
> > >   twice for the same clock.
> > > 
> > > In order to clean this up, use the managed function devm_clk_get() and
> > > store the pointer to the clk in the driver data.
> > > 
> > > Fixes: baffab28b13120694fa3ebab08d3e99667a851d2 ('ARM: Orion: fix driver probe error handling with respect to clk')
> > > Cc: <stable at vger.kernel.org> # v4.5+
> > > Signed-off-by: Simon Baatz <gmbnomis at gmail.com>
> > > ---
> > >  drivers/mtd/nand/orion_nand.c | 42 +++++++++++++++++++++---------------------
> > >  1 file changed, 21 insertions(+), 21 deletions(-)
> > > 
> > > diff --git a/drivers/mtd/nand/orion_nand.c b/drivers/mtd/nand/orion_nand.c
> > > index 4a91c5d000be..b355aa738fae 100644
> > > --- a/drivers/mtd/nand/orion_nand.c
> > > +++ b/drivers/mtd/nand/orion_nand.c
> > > @@ -23,6 +23,11 @@
> > >  #include <asm/sizes.h>
> > >  #include <linux/platform_data/mtd-orion_nand.h>
> > >  
> > > +struct orion_nand_info {
> > > +	struct nand_chip chip;
> > > +	struct clk       *clk;
> > > +};
> > > +
> > >  static void orion_nand_cmd_ctrl(struct mtd_info *mtd, int cmd, unsigned int ctrl)
> > >  {
> > >  	struct nand_chip *nc = mtd_to_nand(mtd);
> > > @@ -75,20 +80,21 @@ static void orion_nand_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
> > >  
> > >  static int __init orion_nand_probe(struct platform_device *pdev)
> > >  {
> > > +	struct orion_nand_info *info;
> > >  	struct mtd_info *mtd;
> > >  	struct nand_chip *nc;
> > >  	struct orion_nand_data *board;
> > >  	struct resource *res;
> > > -	struct clk *clk;
> > >  	void __iomem *io_base;
> > >  	int ret = 0;
> > >  	u32 val = 0;
> > >  
> > > -	nc = devm_kzalloc(&pdev->dev,
> > > -			sizeof(struct nand_chip),
> > > +	info = devm_kzalloc(&pdev->dev,
> > > +			sizeof(struct orion_nand_info),
> > >  			GFP_KERNEL);
> > > -	if (!nc)
> > > +	if (!info)
> > >  		return -ENOMEM;
> > > +	nc = &info->chip;
> > >  	mtd = nand_to_mtd(nc);
> > >  
> > >  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > @@ -145,15 +151,13 @@ static int __init orion_nand_probe(struct platform_device *pdev)
> > >  	if (board->dev_ready)
> > >  		nc->dev_ready = board->dev_ready;
> > >  
> > > -	platform_set_drvdata(pdev, mtd);
> > > +	platform_set_drvdata(pdev, info);
> > >  
> > >  	/* Not all platforms can gate the clock, so it is not
> > >  	   an error if the clock does not exists. */
> > > -	clk = clk_get(&pdev->dev, NULL);
> > > -	if (!IS_ERR(clk)) {
> > > -		clk_prepare_enable(clk);
> > > -		clk_put(clk);
> > > -	}
> > > +	info->clk = devm_clk_get(&pdev->dev, NULL);
> > > +	if (!IS_ERR(info->clk))
> > > +		clk_prepare_enable(info->clk);  
> > 
> > Orthogonal to your patch I suggest:
> > 
> > -	info->clk = devm_clk_get(&pdev->dev, NULL);
> > -	if (!IS_ERR(info->clk))
> > -		clk_prepare_enable(info->clk);
> > +	info->clk = devm_clk_get_optional(&pdev->dev, NULL);
> > +	if (IS_ERR(info->clk)) {
> > +		ret = PTR_ERR(info->clk);
> > +		if (ret != -EPROBE_DEFER)
> > +			dev_err(...);
> > +		return ret;
> > +	}
> > 
> 
> In the meantime, maybe you can do:
> 
> 	info->clk = devm_clk_get(&pdev->dev, NULL);
> 	if (IS_ERR(info->clk)) {
> 		ret = PTR_ERR(info->clk);
> 
> 		if (ret == -ENOENT) {
> 			/*
> 			 * This clk is optional, assign it to NULL when
> 			 * it's not present.
> 			 */
> 			info->clk = NULL;
> 		} else {
> 			if (ret == -EPROBE_DEFER)
> 				dev_err(...);
> 
> 			return ret;
> 		}
> 	}
> 
> This way, you won't have to check the info->clk value when you call
> clk_prepare_enable() or clk_disable_unprepare().
> 

Yes, this makes things simpler. I will add a second patch improving
the error handling in v2 as you and Uwe suggested.


- Simon