Re: [PATCH] mtd: rawnand: mxic: Enable and prepare clocks in probe

[Evgeny Novikov]

Hi Miquel,

On 16.08.2021 11:01, Miquel Raynal wrote:
> Hi Andy,
>
> Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote on Thu, 12 Aug 2021
> 15:13:10 +0300:
>
> > On Thursday, August 12, 2021, Evgeny Novikov <novikov@xxxxxxxxx> wrote:
> >
> > > It seems that mxic_nfc_probe() missed invocation of
> > > mxic_nfc_clk_enable(). The patch fixed that. In addition, error handling
> > > was refined appropriately.
> >
> > NAK. Until you provide a deeper analysis, like how this works before your
> > change.
> >
> >
> > Please, don’t blindly generate patches, this can even your bot do, just
> > think about each change and preferable test on the real hardware.
> >
> > The above is to all your lovely contributions.
> >
> >
> > > Found by Linux Driver Verification project (linuxtesting.org).
> > >
> > > Signed-off-by: Evgeny Novikov <novikov@xxxxxxxxx>
> > > Co-developed-by: Kirill Shilimanov <kirill.shilimanov@xxxxxxxxxx>
> > > Signed-off-by: Kirill Shilimanov <kirill.shilimanov@xxxxxxxxxx>
> > > ---
> > >   drivers/mtd/nand/raw/mxic_nand.c | 16 ++++++++++++----
> > >   1 file changed, 12 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/mtd/nand/raw/mxic_nand.c b/drivers/mtd/nand/raw/mxic_
> > > nand.c
> > > index da1070993994..37e75bf60ee5 100644
> > > --- a/drivers/mtd/nand/raw/mxic_nand.c
> > > +++ b/drivers/mtd/nand/raw/mxic_nand.c
> > > @@ -509,9 +509,15 @@ static int mxic_nfc_probe(struct platform_device
> > > *pdev)
> > >          if (IS_ERR(nfc->send_dly_clk))
> > >                  return PTR_ERR(nfc->send_dly_clk);
> > >
> > > +       err = mxic_nfc_clk_enable(nfc);
> > > +       if (err)
> > > +               return err;
> As Andy said, this is not needed.
>
> > > +
> > >          nfc->regs = devm_platform_ioremap_resource(pdev, 0);
> > > -       if (IS_ERR(nfc->regs))
> > > -               return PTR_ERR(nfc->regs);
> > > +       if (IS_ERR(nfc->regs)) {
> > > +               err = PTR_ERR(nfc->regs);
> > > +               goto fail;
> > > +       }
> > >
> > >          nand_chip = &nfc->chip;
> > >          mtd = nand_to_mtd(nand_chip);
> > > @@ -527,8 +533,10 @@ static int mxic_nfc_probe(struct platform_device
> > > *pdev)
> > >          nand_chip->controller = &nfc->controller;
> > >
> > >          irq = platform_get_irq(pdev, 0);
> > > -       if (irq < 0)
> > > -               return irq;
> > > +       if (irq < 0) {
> > > +               err = irq;
> > > +               goto fail;
> However some reworking is needed in the error path.
>
> That goto statement should be renamed and devm_request_irq() should not
> jump to it.

We still need some help and clarification from those who are very 
familiar with this sort of drivers or/and can test this particular 
driver. mxic_nfc_clk_enable() is the complementary function for 
mxic_nfc_clk_disable(). No other functions invoke 
clk_prepare_enable()/clk_disable_unprepare() in the driver. Unlikely 
somebody in its environment does that since driver specific clocks are 
dealt with. At the moment the driver invokes mxic_nfc_clk_disable() on 
error handling paths in probe, in remove and in mxic_nfc_set_freq(). 
mxic_nfc_clk_enable() is called just by mxic_nfc_set_freq() that 
moreover does this after calling mxic_nfc_clk_disable() first. So, we 
did not find any place in the driver that invokes mxic_nfc_clk_enable() 
prior to mxic_nfc_clk_disable(). Basing on this we added 
mxic_nfc_clk_enable() just after getting clocks. As I explained in the 
previous large e-mail, we may be wrong in our understanding of the 
driver environment or/and at specification of requirements being 
checked. It would be great if you will point out on our mistakes.

Best regards,
Evgeny Novikov
> > > +       }
> > >
> > >          mxic_nfc_hw_init(nfc);
> > >
> > > --
> > > 2.26.2
> > >
> > >   
> Thanks,
> Miquèl