Re: FAILED: patch "[PATCH] counter: stm32-timer-cnt: fix ceiling miss-alignment with" failed to apply to 5.4-stable tree

[Sudip Mukherjee <sudipm.mukherjee@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 367 bytes --]

Hi Greg,

On Mon, Mar 22, 2021 at 10:12:18AM +0100, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 5.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.

Here is the bakport.


--
Regards
Sudip

[-- Attachment #2: 0001-counter-stm32-timer-cnt-fix-ceiling-miss-alignment-w.patch --]
[-- Type: text/x-diff, Size: 3487 bytes --]

From 90f7d51d99c6ebe7e5eb925da018653846eb05bd Mon Sep 17 00:00:00 2001
From: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Date: Wed, 3 Mar 2021 18:49:49 +0100
Subject: [PATCH] counter: stm32-timer-cnt: fix ceiling miss-alignment with
 reload register

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@gmail.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/1614793789-10346-1-git-send-email-fabrice.gasnier@foss.st.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
[sudip: adjuct context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 drivers/counter/stm32-timer-cnt.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/counter/stm32-timer-cnt.c b/drivers/counter/stm32-timer-cnt.c
index 75e08a98d09b..889ea7a6ed63 100644
--- a/drivers/counter/stm32-timer-cnt.c
+++ b/drivers/counter/stm32-timer-cnt.c
@@ -24,7 +24,6 @@ struct stm32_timer_cnt {
 	struct counter_device counter;
 	struct regmap *regmap;
 	struct clk *clk;
-	u32 ceiling;
 	u32 max_arr;
 };
 
@@ -67,14 +66,15 @@ static int stm32_count_write(struct counter_device *counter,
 			     struct counter_count_write_value *val)
 {
 	struct stm32_timer_cnt *const priv = counter->priv;
-	u32 cnt;
+	u32 cnt, ceiling;
 	int err;
 
 	err = counter_count_write_value_get(&cnt, COUNTER_COUNT_POSITION, val);
 	if (err)
 		return err;
 
-	if (cnt > priv->ceiling)
+	regmap_read(priv->regmap, TIM_ARR, &ceiling);
+	if (cnt > ceiling)
 		return -EINVAL;
 
 	return regmap_write(priv->regmap, TIM_CNT, cnt);
@@ -136,10 +136,6 @@ static int stm32_count_function_set(struct counter_device *counter,
 
 	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 */
@@ -197,7 +193,6 @@ static ssize_t stm32_count_ceiling_write(struct counter_device *counter,
 	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, 0);
 	regmap_write(priv->regmap, TIM_ARR, ceiling);
 
-	priv->ceiling = ceiling;
 	return len;
 }
 
@@ -369,7 +364,6 @@ static int stm32_timer_cnt_probe(struct platform_device *pdev)
 
 	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);
-- 
2.30.2