Pali Rohár <[email protected]> writes: > The original CPU voltage value for load L1 is too low for Armada 37xx SoC > when base CPU frequency is 1000 or 1200 MHz. It leads to instabilities > where CPU gets stuck soon after dynamic voltage scaling from load L1 to L0. > > Update the CPU voltage value for load L1 accordingly when base frequency is > 1000 or 1200 MHz. The minimal L1 value for base CPU frequency 1000 MHz is > updated from the original 1.05V to 1.108V and for 1200 MHz is updated to > 1.155V. This minimal L1 value is used only in the case when it is lower > than value for L0. > > This change fixes CPU instability issues on 1 GHz and 1.2 GHz variants of > Espressobin and 1 GHz Turris Mox. > > Marvell previously for 1 GHz variant of Espressobin provided a patch [1] > suitable only for their Marvell Linux kernel 4.4 fork which workarounded > this issue. Patch forced CPU voltage value to 1.108V in all loads. But > such change does not fix CPU instability issues on 1.2 GHz variants of > Armada 3720 SoC. > > During testing we come to the conclusion that using 1.108V as minimal > value for L1 load makes 1 GHz variants of Espressobin and Turris Mox boards > stable. And similarly 1.155V for 1.2 GHz variant of Espressobin. > > These two values 1.108V and 1.155V are documented in Armada 3700 Hardware > Specifications as typical initial CPU voltage values. > > Discussion about this issue is also at the Armbian forum [2]. > > [1] - > https://github.com/MarvellEmbeddedProcessors/linux-marvell/commit/dc33b62c90696afb6adc7dbcc4ebbd48bedec269 > [2] - https://forum.armbian.com/topic/10429-how-to-make-espressobin-v7-stable/ > > Signed-off-by: Pali Rohár <[email protected]> > Tested-by: Tomasz Maciej Nowak <[email protected]> > Tested-by: Anders Trier Olesen <[email protected]> > Tested-by: Philip Soares <[email protected]> > Fixes: 1c3528232f4b ("cpufreq: armada-37xx: Add AVS support") > Cc: [email protected]
Acked-by: Gregory CLEMENT <[email protected]> Thanks, Gregory > --- > drivers/cpufreq/armada-37xx-cpufreq.c | 37 +++++++++++++++++++++++++++ > 1 file changed, 37 insertions(+) > > diff --git a/drivers/cpufreq/armada-37xx-cpufreq.c > b/drivers/cpufreq/armada-37xx-cpufreq.c > index b8dc6c849579..c7683d447b11 100644 > --- a/drivers/cpufreq/armada-37xx-cpufreq.c > +++ b/drivers/cpufreq/armada-37xx-cpufreq.c > @@ -73,6 +73,8 @@ > #define LOAD_LEVEL_NR 4 > > #define MIN_VOLT_MV 1000 > +#define MIN_VOLT_MV_FOR_L1_1000MHZ 1108 > +#define MIN_VOLT_MV_FOR_L1_1200MHZ 1155 > > /* AVS value for the corresponding voltage (in mV) */ > static int avs_map[] = { > @@ -208,6 +210,8 @@ static u32 armada_37xx_avs_val_match(int target_vm) > * - L2 & L3 voltage should be about 150mv smaller than L0 voltage. > * This function calculates L1 & L2 & L3 AVS values dynamically based > * on L0 voltage and fill all AVS values to the AVS value table. > + * When base CPU frequency is 1000 or 1200 MHz then there is additional > + * minimal avs value for load L1. > */ > static void __init armada37xx_cpufreq_avs_configure(struct regmap *base, > struct armada_37xx_dvfs *dvfs) > @@ -239,6 +243,19 @@ static void __init > armada37xx_cpufreq_avs_configure(struct regmap *base, > for (load_level = 1; load_level < LOAD_LEVEL_NR; load_level++) > dvfs->avs[load_level] = avs_min; > > + /* > + * Set the avs values for load L0 and L1 when base CPU frequency > + * is 1000/1200 MHz to its typical initial values according to > + * the Armada 3700 Hardware Specifications. > + */ > + if (dvfs->cpu_freq_max >= 1000*1000*1000) { > + if (dvfs->cpu_freq_max >= 1200*1000*1000) > + avs_min = > armada_37xx_avs_val_match(MIN_VOLT_MV_FOR_L1_1200MHZ); > + else > + avs_min = > armada_37xx_avs_val_match(MIN_VOLT_MV_FOR_L1_1000MHZ); > + dvfs->avs[0] = dvfs->avs[1] = avs_min; > + } > + > return; > } > > @@ -258,6 +275,26 @@ static void __init > armada37xx_cpufreq_avs_configure(struct regmap *base, > target_vm = avs_map[l0_vdd_min] - 150; > target_vm = target_vm > MIN_VOLT_MV ? target_vm : MIN_VOLT_MV; > dvfs->avs[2] = dvfs->avs[3] = armada_37xx_avs_val_match(target_vm); > + > + /* > + * Fix the avs value for load L1 when base CPU frequency is 1000/1200 > MHz, > + * otherwise the CPU gets stuck when switching from load L1 to load L0. > + * Also ensure that avs value for load L1 is not higher than for L0. > + */ > + if (dvfs->cpu_freq_max >= 1000*1000*1000) { > + u32 avs_min_l1; > + > + if (dvfs->cpu_freq_max >= 1200*1000*1000) > + avs_min_l1 = > armada_37xx_avs_val_match(MIN_VOLT_MV_FOR_L1_1200MHZ); > + else > + avs_min_l1 = > armada_37xx_avs_val_match(MIN_VOLT_MV_FOR_L1_1000MHZ); > + > + if (avs_min_l1 > dvfs->avs[0]) > + avs_min_l1 = dvfs->avs[0]; > + > + if (dvfs->avs[1] < avs_min_l1) > + dvfs->avs[1] = avs_min_l1; > + } > } > > static void __init armada37xx_cpufreq_avs_setup(struct regmap *base, > -- > 2.20.1 > -- Gregory Clement, Bootlin Embedded Linux and Kernel engineering http://bootlin.com
