thara gopinath <[email protected]> writes: > From: Thara Gopinath <[email protected]> > > In the current opp layer the frequency matching API's > tries to match the exact frequency passed in Hz. This leads > to problems in cases where dplls are locked to slightly differnet > frequencies due to sys clock speed or optimum M,N values. > Consider the following scenario > a. dpll_x is supposed to be locked at 266Mhz but is > actually att 266.045 Mhz due to above mentioned reasons. > b. The opp table has the entry as 266000000 hz. > c. The user does a clk_get_rate(dpll_x) and passes the > corresponding rate <rate> into the opp API's to get back > a opp table entry. > d. In this scenario if the user has called into > opp_find_freq_exact it will return an error. > If the user has called into opp_find_freq_ceil > it will either return the opp entry corresponding > to the next higher frequency in the opp table > or return an error if 266 Mhz is the last entry > in the table. > > The above is not correct as we expect the framework to return back > the opp table entry corresponding to 266 Mhz. > > Now there are two ways of fixing this issue. > a. Put the correct dpll lock frequency in the opp table. > This means opp table will now have entries like 266045000 hz. > But this is not scalable as these dpll lock frequencies > can change slightly based on sys clk speeds. Like for eg > at sys clk speed 38.4 Mhz we will able to get 266.045 Mhz > where as at sys clk speed 26 Mhz we will be able to get > onyl 266.124 Mhz etc. So depending on the platform we > will have to start changing the opp table. > > b. Do the comparison in Mhz in the opp layer rather than in Hz. > This would mean we will divide the rate passed into the opp layer > API and the rates stored in the opp tables by 1000000 to get the > rates in Mhz and do the necessary comparision. In this approach any > vague frequency like 266.045Mhz will get mapped to 266 Mhz in the > opp table. But if the passed rate is 267 Mhz, the opp framework > will still rerturn an error or the next highest opp table entry > > This patch implements solution b. The scenario mentioned above is > esp true for OMAP4 dpll_iva where we do end up with such weird frequencies > due to sys clk being at 38.4 Mhz.
I agree that solution b is better, although it makes the '_exact' function a bit less exact. :/ solution b is fine with me, but the kerneldoc for these find functions should be updated to describe the new matching technique. Kevin > Signed-off-by: Thara Gopinath <[email protected]> > --- > arch/arm/plat-omap/opp.c | 37 ++++++++++++++++++++++++++----------- > 1 files changed, 26 insertions(+), 11 deletions(-) > > diff --git a/arch/arm/plat-omap/opp.c b/arch/arm/plat-omap/opp.c > index b9b7bda..ba7a554 100644 > --- a/arch/arm/plat-omap/opp.c > +++ b/arch/arm/plat-omap/opp.c > @@ -212,15 +212,20 @@ struct omap_opp *opp_find_freq_exact(struct device *dev, > { > struct device_opp *dev_opp; > struct omap_opp *temp_opp, *opp = ERR_PTR(-ENODEV); > + unsigned long req_freq = freq / 1000000; > > dev_opp = find_device_opp(dev); > if (IS_ERR(dev_opp)) > return opp; > > list_for_each_entry(temp_opp, &dev_opp->opp_list, node) { > - if (temp_opp->enabled && temp_opp->rate == freq) { > - opp = temp_opp; > - break; > + if (temp_opp->enabled) { > + unsigned long rate = temp_opp->rate / 1000000; > + > + if (rate == req_freq) { > + opp = temp_opp; > + break; > + } > } > } > > @@ -258,16 +263,21 @@ struct omap_opp *opp_find_freq_ceil(struct device *dev, > unsigned long *freq) > { > struct device_opp *dev_opp; > struct omap_opp *temp_opp, *opp = ERR_PTR(-ENODEV); > + unsigned long req_freq = *freq / 1000000; > > dev_opp = find_device_opp(dev); > if (IS_ERR(dev_opp)) > return opp; > > list_for_each_entry(temp_opp, &dev_opp->opp_list, node) { > - if (temp_opp->enabled && temp_opp->rate >= *freq) { > - opp = temp_opp; > - *freq = opp->rate; > - break; > + if (temp_opp->enabled) { > + unsigned long rate = temp_opp->rate / 1000000; > + > + if (rate >= req_freq) { > + opp = temp_opp; > + *freq = opp->rate; > + break; > + } > } > } > > @@ -305,16 +315,21 @@ struct omap_opp *opp_find_freq_floor(struct device > *dev, unsigned long *freq) > { > struct device_opp *dev_opp; > struct omap_opp *temp_opp, *opp = ERR_PTR(-ENODEV); > + unsigned long req_freq = *freq / 1000000; > > dev_opp = find_device_opp(dev); > if (IS_ERR(dev_opp)) > return opp; > > list_for_each_entry_reverse(temp_opp, &dev_opp->opp_list, node) { > - if (temp_opp->enabled && temp_opp->rate <= *freq) { > - opp = temp_opp; > - *freq = opp->rate; > - break; > + if (temp_opp->enabled) { > + unsigned long rate = temp_opp->rate / 1000000; > + > + if (rate <= req_freq) { > + opp = temp_opp; > + *freq = opp->rate; > + break; > + } > } > } -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
