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

Boris Brezillon
2017-03-17T06:36:57Z

On Thu, 16 Mar 2017 22:50:31 +0100
Simon Baatz <gmbnomis@gmail.com> wrote:

> 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@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)

I meant != -EPROBE_DEFER here.

> > 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