Re: [PATCH v2 06/12] mtd: rawnand: stm32_fmc2: use FMC2_TIMEOUT_MS for timeouts

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On 4/29/20 12:06 PM, Miquel Raynal wrote:
Hi Christophe,

Christophe Kerello <christophe.kerello@xxxxxx> wrote on Wed, 29 Apr
2020 11:41:44 +0200:

On 4/29/20 11:35 AM, Miquel Raynal wrote:
Hi Christophe,

Christophe Kerello <christophe.kerello@xxxxxx> wrote on Wed, 29 Apr
2020 11:27:43 +0200:
Hi Miquèl,

On 4/27/20 8:22 PM, Miquel Raynal wrote:
Hi Christophe,

Christophe Kerello <christophe.kerello@xxxxxx> wrote on Wed, 15 Apr
2020 17:57:30 +0200:
    >>>> This patch removes the constant FMC2_TIMEOUT_US.
FMC2_TIMEOUT_MS is set to 5 seconds and this constant is used
each time that we need to wait (except when the timeout value
is set by the framework)

Signed-off-by: Christophe Kerello <christophe.kerello@xxxxxx>
---
    drivers/mtd/nand/raw/stm32_fmc2_nand.c | 11 +++++------
    1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/nand/raw/stm32_fmc2_nand.c b/drivers/mtd/nand/raw/stm32_fmc2_nand.c
index ab53314..f159c39 100644
--- a/drivers/mtd/nand/raw/stm32_fmc2_nand.c
+++ b/drivers/mtd/nand/raw/stm32_fmc2_nand.c
@@ -37,8 +37,7 @@
    /* Max ECC buffer length */
    #define FMC2_MAX_ECC_BUF_LEN		(FMC2_BCHDSRS_LEN * FMC2_MAX_SG)
    >> -#define FMC2_TIMEOUT_US			1000
-#define FMC2_TIMEOUT_MS			1000
+#define FMC2_TIMEOUT_MS			5000
    >>   /* Timings */
    #define FMC2_THIZ			1
@@ -525,9 +524,9 @@ static int stm32_fmc2_ham_calculate(struct nand_chip *chip, const u8 *data,
    	u32 sr, heccr;
    	int ret;
    >> -	ret = readl_relaxed_poll_timeout(fmc2->io_base + FMC2_SR,
-					 sr, sr & FMC2_SR_NWRF, 10,
-					 FMC2_TIMEOUT_MS);
+	ret = readl_relaxed_poll_timeout_atomic(fmc2->io_base + FMC2_SR,
+						sr, sr & FMC2_SR_NWRF, 1,
+						1000 * FMC2_TIMEOUT_MS);

Is the _atomic suffix needed here? If yes it would deserve a separate
patch with Fixes/Stable tags.
    >>
I have currently not seen any issues. So, I will remove this modification as we will move to regmap_read_poll_timeout in patch 10.
    	if (ret) {
    		dev_err(fmc2->dev, "ham timeout\n");
    		return ret;
@@ -1315,7 +1314,7 @@ static int stm32_fmc2_waitrdy(struct nand_chip *chip, unsigned long timeout_ms)
    	/* Check if there is no pending requests to the NAND flash */
    	if (readl_relaxed_poll_timeout_atomic(fmc2->io_base + FMC2_SR, sr,
    					      sr & FMC2_SR_NWRF, 1,
-					      FMC2_TIMEOUT_US))
+					      1000 * FMC2_TIMEOUT_MS))
    		dev_warn(fmc2->dev, "Waitrdy timeout\n");
    >>   	/* Wait tWB before R/B# signal is low */

You change the timeouts from 1ms to 5s.

Maybe 5s is a little bit too much IMHO but we don't really care as this
is a timeout. However 1ms is tight. If you are changing this value
because it triggers error (eg. when the machine is loaded), then it is
a fix and should appear like it.

Thanks,
Miquèl
    >>
No errors currently happens.
During our stress tests, in a overloaded system, we have seen that we could be close to 1 second, even if we never met this value.
So, to be safe, I have set this timeout to 5 seconds.
As it is just a timeout value, I have not seen any side effect.
I am using the same timeout constant to avoid to have one timeout per cases.

Something is wrong in my mind:
You say you observe delays of almost up to 1 second, but the polling
currently happens on 1000 us = 1ms, either you had timeouts or I
misread something?

Thanks,
Miquèl

Hi Miquèl,

My fault. For this polling, we never met 1 ms.
The 1 second observed was on the sequencer when we read/write a page (as it the same timeout value that is used)

OK I get it. So perhaps you can give these details in the commit log to
explain why you use 5 seconds instead of one.

Thanks,
Miquèl


Hi Miquèl,

A proposal could also be to split this patch:
 - a first patch that is using only one timeout value.
 - a second patch that is increasing the value to 5 seconds.

Regards,
Christophe Kerello.

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