Nishanth Menon <nm@xxxxxx> writes: > From: Yuan Jiangli <jlyuan@xxxxxxxxxxxx> > > commit 2f34ce81b8c05c900e45bd88595cc154f7bb5957 > (OMAP3: PM: Adding voltage driver support.) > introduced runtime computation of waittime to handle all potential > sys clocks available. > > In the voltage processor, the SPMSUpdateWait is calculated based on > the slew rate and the voltage step (SMPSUpdateWait = slew rate * > Voltage Step). After the voltage processor receives the SMPS_Ack > signal, the Voltage Controller will wait for SMPSUpdateWait clock > cycles for the voltage to settle to the new value. For all > practical purposes, the waittime parameter is the OMAP hardware > translation of what the slew rate on the PMIC is. > > As an example, with TPS62361 on OMAP4460, > step_size = 10000 > slew_rate = 32000 > sys_clk_rate = 38400 > > Our current computation results in the following: > = ((step_size / slew_rate) * sys_clk_rate) / 1000 > = ((10000 / 32000) * 38400 / 1000 > = 0 > > Fix the same using DIV_ROUND_UP as an extra wait clock cycle > is better than lesser clock cycle. For the above example, this > translates to: > = (10000 * 38400) / (1000 * 32000) > = 12 > > Acked-by: Jon Hunter <jon-hunter@xxxxxx> > [nm@xxxxxx: slightly better implementation] > Signed-off-by: Nishanth Menon <nm@xxxxxx> > Signed-off-by: Yuan Jiangli <jlyuan@xxxxxxxxxxxx> Acked-by: Kevin Hilman <khilman@xxxxxx> Tony, I don't have any more PM fixes for this cycle, so feel free to add this to fixes-non-critical-part2. This is an important fix, but since we're not doing active voltage scaling in mainline today, I don't think it's 3.3 material. Kevin > --- > arch/arm/mach-omap2/vp.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/mach-omap2/vp.c b/arch/arm/mach-omap2/vp.c > index 0df8882..f95c1ba 100644 > --- a/arch/arm/mach-omap2/vp.c > +++ b/arch/arm/mach-omap2/vp.c > @@ -61,8 +61,8 @@ void __init omap_vp_init(struct voltagedomain *voltdm) > vddmin = voltdm->pmic->vp_vddmin; > vddmax = voltdm->pmic->vp_vddmax; > > - waittime = ((voltdm->pmic->step_size / voltdm->pmic->slew_rate) * > - sys_clk_rate) / 1000; > + waittime = DIV_ROUND_UP(voltdm->pmic->step_size * sys_clk_rate, > + 1000 * voltdm->pmic->slew_rate); > vstepmin = voltdm->pmic->vp_vstepmin; > vstepmax = voltdm->pmic->vp_vstepmax; -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
