diff options
Diffstat (limited to 'drivers/clk/mvebu/armada-37xx-periph.c')
| -rw-r--r-- | drivers/clk/mvebu/armada-37xx-periph.c | 47 |
1 files changed, 39 insertions, 8 deletions
diff --git a/drivers/clk/mvebu/armada-37xx-periph.c b/drivers/clk/mvebu/armada-37xx-periph.c index 6860bd5a37c5..499f5962c8b0 100644 --- a/drivers/clk/mvebu/armada-37xx-periph.c +++ b/drivers/clk/mvebu/armada-37xx-periph.c @@ -1,3 +1,4 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Marvell Armada 37xx SoC Peripheral clocks * @@ -5,10 +6,6 @@ * * Gregory CLEMENT <gregory.clement@free-electrons.com> * - * This file is licensed under the terms of the GNU General Public - * License version 2 or later. This program is licensed "as is" - * without any warranty of any kind, whether express or implied. - * * Most of the peripheral clocks can be modelled like this: * _____ _______ _______ * TBG-A-P --| | | | | | ______ @@ -35,6 +32,7 @@ #define CLK_SEL 0x10 #define CLK_DIS 0x14 +#define ARMADA_37XX_DVFS_LOAD_1 1 #define LOAD_LEVEL_NR 4 #define ARMADA_37XX_NB_L0L1 0x18 @@ -418,7 +416,6 @@ static unsigned int armada_3700_pm_dvfs_get_cpu_parent(struct regmap *base) static u8 clk_pm_cpu_get_parent(struct clk_hw *hw) { struct clk_pm_cpu *pm_cpu = to_clk_pm_cpu(hw); - int num_parents = clk_hw_get_num_parents(hw); u32 val; if (armada_3700_pm_dvfs_is_enabled(pm_cpu->nb_pm_base)) { @@ -428,9 +425,6 @@ static u8 clk_pm_cpu_get_parent(struct clk_hw *hw) val &= pm_cpu->mask_mux; } - if (val >= num_parents) - return -EINVAL; - return val; } @@ -507,6 +501,40 @@ static long clk_pm_cpu_round_rate(struct clk_hw *hw, unsigned long rate, return -EINVAL; } +/* + * Switching the CPU from the L2 or L3 frequencies (300 and 200 Mhz + * respectively) to L0 frequency (1.2 Ghz) requires a significant + * amount of time to let VDD stabilize to the appropriate + * voltage. This amount of time is large enough that it cannot be + * covered by the hardware countdown register. Due to this, the CPU + * might start operating at L0 before the voltage is stabilized, + * leading to CPU stalls. + * + * To work around this problem, we prevent switching directly from the + * L2/L3 frequencies to the L0 frequency, and instead switch to the L1 + * frequency in-between. The sequence therefore becomes: + * 1. First switch from L2/L3(200/300MHz) to L1(600MHZ) + * 2. Sleep 20ms for stabling VDD voltage + * 3. Then switch from L1(600MHZ) to L0(1200Mhz). + */ +static void clk_pm_cpu_set_rate_wa(unsigned long rate, struct regmap *base) +{ + unsigned int cur_level; + + if (rate != 1200 * 1000 * 1000) + return; + + regmap_read(base, ARMADA_37XX_NB_CPU_LOAD, &cur_level); + cur_level &= ARMADA_37XX_NB_CPU_LOAD_MASK; + if (cur_level <= ARMADA_37XX_DVFS_LOAD_1) + return; + + regmap_update_bits(base, ARMADA_37XX_NB_CPU_LOAD, + ARMADA_37XX_NB_CPU_LOAD_MASK, + ARMADA_37XX_DVFS_LOAD_1); + msleep(20); +} + static int clk_pm_cpu_set_rate(struct clk_hw *hw, unsigned long rate, unsigned long parent_rate) { @@ -537,6 +565,9 @@ static int clk_pm_cpu_set_rate(struct clk_hw *hw, unsigned long rate, */ reg = ARMADA_37XX_NB_CPU_LOAD; mask = ARMADA_37XX_NB_CPU_LOAD_MASK; + + clk_pm_cpu_set_rate_wa(rate, base); + regmap_update_bits(base, reg, mask, load_level); return rate; |