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

Boris Brezillon
2017-03-16T09:12:11Z

On Mon, 13 Mar 2017 08:12:41 +0100
Uwe Kleine-König <u.kleine-koenig@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@vger.kernel.org> # v4.5+
> > Signed-off-by: Simon Baatz <gmbnomis@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().