Messages in this thread | | | Subject | Re: [PATCH v2] dec: tulip: de4x5: Replace mdelay with usleep_range in de4x5_hw_init | From | arvindY <> | Date | Thu, 12 Apr 2018 07:51:42 +0530 |
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On Thursday 12 April 2018 07:00 AM, Jia-Ju Bai wrote: > > > 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(). >
James is right, You have added all usleep_range() during system boot-up time. During boot-up system will run as single threaded. Where this change will not make much sense. System first priority is match the exact timing on each and every boot-up.
~arvind
> > Best wishes, > Jia-Ju Bai
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