This is a note to let you know that I've just added the patch titled counter: stm32-timer-cnt: fix ceiling miss-alignment with reload register to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: counter-stm32-timer-cnt-fix-ceiling-miss-alignment-with-reload-register.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From b14d72ac731753708a7c1a6b3657b9312b6f0042 Mon Sep 17 00:00:00 2001 From: Fabrice Gasnier <fabrice.gasnier@xxxxxxxxxxx> Date: Wed, 3 Mar 2021 18:49:49 +0100 Subject: counter: stm32-timer-cnt: fix ceiling miss-alignment with reload register From: Fabrice Gasnier <fabrice.gasnier@xxxxxxxxxxx> commit b14d72ac731753708a7c1a6b3657b9312b6f0042 upstream. Ceiling value may be miss-aligned with what's actually configured into the ARR register. This is seen after probe as currently the ARR value is zero, whereas ceiling value is set to the maximum. So: - reading ceiling reports zero - in case the counter gets enabled without any prior configuration, it won't count. - in case the function gets set by the user 1st, (priv->ceiling) is used. Fix it by getting rid of the cached "priv->ceiling" variable. Rather use the ARR register value directly by using regmap read or write when needed. There should be no drawback on performance as priv->ceiling isn't used in performance critical path. There's also no point in writing ARR while setting function (sms), so it can be safely removed. Fixes: ad29937e206f ("counter: Add STM32 Timer quadrature encoder") Suggested-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxxxxxxx> Acked-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx> Cc: <Stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/1614793789-10346-1-git-send-email-fabrice.gasnier@xxxxxxxxxxx Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/counter/stm32-timer-cnt.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) --- a/drivers/counter/stm32-timer-cnt.c +++ b/drivers/counter/stm32-timer-cnt.c @@ -31,7 +31,6 @@ struct stm32_timer_cnt { struct counter_device counter; struct regmap *regmap; struct clk *clk; - u32 ceiling; u32 max_arr; bool enabled; struct stm32_timer_regs bak; @@ -75,8 +74,10 @@ static int stm32_count_write(struct coun const unsigned long val) { struct stm32_timer_cnt *const priv = counter->priv; + u32 ceiling; - if (val > priv->ceiling) + regmap_read(priv->regmap, TIM_ARR, &ceiling); + if (val > ceiling) return -EINVAL; return regmap_write(priv->regmap, TIM_CNT, val); @@ -138,10 +139,6 @@ static int stm32_count_function_set(stru regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, 0); - /* TIMx_ARR register shouldn't be buffered (ARPE=0) */ - regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, 0); - regmap_write(priv->regmap, TIM_ARR, priv->ceiling); - regmap_update_bits(priv->regmap, TIM_SMCR, TIM_SMCR_SMS, sms); /* Make sure that registers are updated */ @@ -199,7 +196,6 @@ static ssize_t stm32_count_ceiling_write regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, 0); regmap_write(priv->regmap, TIM_ARR, ceiling); - priv->ceiling = ceiling; return len; } @@ -374,7 +370,6 @@ static int stm32_timer_cnt_probe(struct priv->regmap = ddata->regmap; priv->clk = ddata->clk; - priv->ceiling = ddata->max_arr; priv->max_arr = ddata->max_arr; priv->counter.name = dev_name(dev); Patches currently in stable-queue which might be from fabrice.gasnier@xxxxxxxxxxx are queue-5.10/counter-stm32-timer-cnt-report-count-function-when-s.patch queue-5.10/counter-stm32-timer-cnt-fix-ceiling-write-max-value.patch queue-5.10/counter-stm32-timer-cnt-fix-ceiling-miss-alignment-with-reload-register.patch