Hi Nishanth, > On 02/03/2017 05:21 PM, Lukasz Majewski wrote: > > Hi Dave, > > > > Thanks for sharing the knowledge :-) > > > >> On 02/03/2017 09:24 AM, Lukasz Majewski wrote: > >>> The "opp_high" property brings support for 1.5 GHz CPU frequency > >>> for TI's am57xx line of processors. > >>> > >>> Signed-off-by: Lukasz Majewski <lukma@xxxxxxx> > >>> --- > >>> arch/arm/boot/dts/dra7.dtsi | 5 +++++ > >>> 1 file changed, 5 insertions(+) > >>> > >> > >> This can't be blindly enabled for all am57xx SoCs, > > > > Yes, I'm fully aware of AVS, which uses fuses and SoC silicon > > revision to assess if frequency can be enabled. > > > > Example from my playground: > > > > - AM5728 works with 1.5 GHz enabled > > > > - AM5718 hangs when I try to enable 1.5 GHz frequency > > > > > >> there is a > >> forthcoming ti-cpufreq [1] driver > > > > I've backported and tested this code on v4.9 vanilla. It works :-) > > > >> that is needed that will decided > >> which OPPs can and cannot be enabled for the specific variant in > >> use. > > > > I do have a question: > > > > Do you know the correct opp-supported-hw value for 1.5 GHz on AM57x8 > > SoC? > > In TI's SDK Linux (v4.4): opp-supported-hw = <0xFF 0x04>; but this > > seems to be always enabled (and not taking silicon revision and > > efuse into account). > > There is a TISDK 4.9 being built up as well (we typically do let the > driver soak for a test cycle prior to posting it upstream) but if it > is of interest.. it should match the version Dave posted upstream.. > > http://git.ti.com/ti-linux-kernel/ti-linux-kernel/blobs/ti-lsk-linux-4.9.y/arch/arm/boot/dts/dra7.dtsi#line100 This opp_table0 DTS node definition is different than the one sent to ML by Dave (e.g. opp-microvolt has different definition). > > > For my use case it would be best to see what data should prevent my > > AM5718 from 1.5 GHz OPP. > > > > In other words I need to be 100% sure that my silicon SoC version > > doesn't support the 1.5 GHz frequency. > > > > look at dra7_efuse_xlate which does a speed grade decode of the > speeds permitted.. a value of 15 or 23 should permit 1.5GHz. those > are common for DRA7/AM57 SoCs. Ok, I've checked this and both SoCs have value 23, so they should support 1.5 GHz operation. Hence, the AM5718 should not hang. > > If the efuses seem set for 1.5GHz, the chip should be capable of > 1.5GHz, i'd start suspecting regulators, slew rates and the like. Then I do need to examine them. > > http://www.ti.com/lit/pdf/spruhz7 > rev d: page 371 -> 23 (0x17) = X speed designator Refer to device DM > for supported speed grades for a given device, and the definition for > supported speed grades. > So, if you go to > http://www.ti.com/product/AM5718/datasheet/specifications#SWPS043-7245x > -> you will see the "X" designator in AM5718xxX which does support 23 > and 1.5GHz. Yes, correct. > > > Now, if you did get one of the pre-production samples, Is there any prod_id (or any other register value), which indicates the production sample? > it is possible > to have efuses slightly messed up on very initial samples - at least > internally, we have had them replaced and none of those samples > should have exited TI.. but mistakes might happen.. if the efuse > value does not meet the speed grade in documentation, then, please > contact TI FAE your company works with and let them know for what to > do alternatively, you can also file it on e2e.ti.com for further > support. > Thanks for support. Best regards, Lukasz Majewski -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@xxxxxxx -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
