linux-kernel - Re: [PATCH v1] hwmon: (ucd90320) Increase delay from 250 to 500us

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Message-ID: <a924a55d-f591-498d-b80e-4889ed6691e9@linux.ibm.com>
Date: Wed, 8 May 2024 10:16:14 -0500
From: Eddie James <eajames@...ux.ibm.com>
To: Lakshmi Yadlapati <lakshmiy@...ibm.com>, jdelvare@...e.com,
        linux@...ck-us.net
Cc: ninad@...ux.ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] hwmon: (ucd90320) Increase delay from 250 to 500us


On 5/7/24 14:46, Lakshmi Yadlapati wrote:
> Following the failure observed with a delay of 250us, experiments were
> conducted with various delays. It was found that a delay of 350us
> effectively mitigated the issue.
>
> To provide a more optimal solution while still allowing a margin for
> stability, the delay is being adjusted to 500us.


Reviewed-by: Eddie James <eajames@...ux.ibm.com>


>
> Signed-off-by: Lakshmi Yadlapati <lakshmiy@...ibm.com>
> ---
>   drivers/hwmon/pmbus/ucd9000.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hwmon/pmbus/ucd9000.c b/drivers/hwmon/pmbus/ucd9000.c
> index 8d9d422450e5..d817c719b90b 100644
> --- a/drivers/hwmon/pmbus/ucd9000.c
> +++ b/drivers/hwmon/pmbus/ucd9000.c
> @@ -80,11 +80,11 @@ struct ucd9000_debugfs_entry {
>    * It has been observed that the UCD90320 randomly fails register access when
>    * doing another access right on the back of a register write. To mitigate this
>    * make sure that there is a minimum delay between a write access and the
> - * following access. The 250us is based on experimental data. At a delay of
> - * 200us the issue seems to go away. Add a bit of extra margin to allow for
> + * following access. The 500 is based on experimental data. At a delay of
> + * 350us the issue seems to go away. Add a bit of extra margin to allow for
>    * system to system differences.
>    */
> -#define UCD90320_WAIT_DELAY_US 250
> +#define UCD90320_WAIT_DELAY_US 500
>   
>   static inline void ucd90320_wait(const struct ucd9000_data *data)
>   {