Re: [PATCH v2] dec: tulip: de4x5: Replace mdelay with usleep_range in de4x5_hw_init

[Jia-Ju Bai]

On 2018/4/12 0:16, James Bottomley wrote:
> On Wed, 2018-04-11 at 23:39 +0800, Jia-Ju Bai wrote:
> > de4x5_hw_init() is never called in atomic context.
> >
> > de4x5_hw_init() is only called by de4x5_pci_probe(), which is only
> > set as ".probe" in struct pci_driver.
> >
> > Despite never getting called from atomic context, de4x5_hw_init()
> > calls mdelay() to busily wait. This is not necessary and can be
> > replaced with usleep_range() to  avoid busy waiting.
> >
> > This is found by a static analysis tool named DCNS written by myself.
> > And I also manually check it.
> Did you actually test this?  The usual reason for wanting m/udelay is
> that the timing must be exact.  The driver is filled with mdelay()s for
> this reason.  The one you've picked on is in the init path so it won't
> affect the runtime in any way.  I also don't think we have the hrtimer
> machinery for usleep_range() to work properly on parisc, so I don't
> think the replacement works.
>
> James

Hello, James.
Thanks for your reply :)

I agree that usleep_range() here will not much affect the real execution 
of this driver.

But I think usleep_range() can more opportunity for other threads to use 
the CPU core to schedule during waiting.
That is why I detect mdelay() that can be replaced with msleep() or 
usleep_range().


Best wishes,
Jia-Ju Bai