Messages in this thread | | | Date | Tue, 12 Mar 2013 06:27:19 -0700 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH 1/6] platform-drivers: msm: add single-wire serial bus interface (SSBI) driver |
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On Mon, Mar 11, 2013 at 11:51:08PM -0700, David Brown wrote: > Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes: > > >> +static int ssbi_wait_mask(struct msm_ssbi *ssbi, u32 set_mask, u32 clr_mask) > >> +{ > >> + u32 timeout = SSBI_TIMEOUT_US; > >> + u32 val; > >> + > >> + while (timeout--) { > >> + val = ssbi_readl(ssbi, SSBI2_STATUS); > >> + if (((val & set_mask) == set_mask) && ((val & clr_mask) == 0)) > >> + return 0; > >> + udelay(1); > > > > Busy loop? Really? > > Finally was able to dig up some of the reason for this. The > transactions typically take about 5us. In the case of contention with > another CPU, it could take as much as 20us. > > Would it be sufficient to just explain this in a comment?
That would be good to do, especially if it turns out to be a longer delay and people start to wonder why their system load is increasing for no noticeable reason.
thanks,
greg k-h
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