| From 0c21e3c5d0bdc28a8e33d931e4df282384e9bcfa Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Wed, 3 Mar 2021 18:51:35 +0100 |
| Subject: mfd: stm32-timers: Avoid clearing auto reload register |
| |
| From: Fabrice Gasnier <fabrice.gasnier@foss.st.com> |
| |
| [ Upstream commit 4917e498c6894ba077867aff78f82cffd5ffbb5c ] |
| |
| The ARR register is cleared unconditionally upon probing, after the maximum |
| value has been read. This initial condition is rather not intuitive, when |
| considering the counter child driver. It rather expects the maximum value |
| by default: |
| - The counter interface shows a zero value by default for 'ceiling' |
| attribute. |
| - Enabling the counter without any prior configuration makes it doesn't |
| count. |
| |
| The reset value of ARR register is the maximum. So Choice here |
| is to backup it, and restore it then, instead of clearing its value. |
| It also fixes the initial condition seen by the counter driver. |
| |
| Fixes: d0f949e220fd ("mfd: Add STM32 Timers driver") |
| Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com> |
| Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com> |
| Signed-off-by: Lee Jones <lee.jones@linaro.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| drivers/mfd/stm32-timers.c | 7 ++++++- |
| 1 file changed, 6 insertions(+), 1 deletion(-) |
| |
| diff --git a/drivers/mfd/stm32-timers.c b/drivers/mfd/stm32-timers.c |
| index add603359124..44ed2fce0319 100644 |
| --- a/drivers/mfd/stm32-timers.c |
| +++ b/drivers/mfd/stm32-timers.c |
| @@ -158,13 +158,18 @@ static const struct regmap_config stm32_timers_regmap_cfg = { |
| |
| static void stm32_timers_get_arr_size(struct stm32_timers *ddata) |
| { |
| + u32 arr; |
| + |
| + /* Backup ARR to restore it after getting the maximum value */ |
| + regmap_read(ddata->regmap, TIM_ARR, &arr); |
| + |
| /* |
| * Only the available bits will be written so when readback |
| * we get the maximum value of auto reload register |
| */ |
| regmap_write(ddata->regmap, TIM_ARR, ~0L); |
| regmap_read(ddata->regmap, TIM_ARR, &ddata->max_arr); |
| - regmap_write(ddata->regmap, TIM_ARR, 0x0); |
| + regmap_write(ddata->regmap, TIM_ARR, arr); |
| } |
| |
| static int stm32_timers_dma_probe(struct device *dev, |
| -- |
| 2.30.2 |
| |