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 Change-Id: I0ee22e60555e1cfd6cc3dea7ee44d0584ce182b6 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> --- 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; -- 1.7.5.4 -- 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
