linux-kernel - Re: [PATCH v2 2/2] hwmon (occ): Retry for checksum failure

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Date:   Wed, 27 Apr 2022 08:34:25 +0000
From:   Joel Stanley <joel@....id.au>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     linux-fsi@...ts.ozlabs.org, linux-hwmon@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Jeremy Kerr <jk@...abs.org>,
        David Laight <David.Laight@...lab.com>
Subject: Re: [PATCH v2 2/2] hwmon (occ): Retry for checksum failure

On Tue, 26 Apr 2022 at 15:50, Eddie James <eajames@...ux.ibm.com> wrote:
>
> Due to the OCC communication design with a shared SRAM area,
> checkum errors are expected due to corrupted buffer from OCC
> communications with other system components. Therefore, retry
> the command twice in the event of a checksum failure.
>
> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
> Acked-by: Guenter Roeck <linux@...ck-us.net>
> ---
>  drivers/hwmon/occ/p9_sbe.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/hwmon/occ/p9_sbe.c b/drivers/hwmon/occ/p9_sbe.c
> index 49b13cc01073..e6ccef2af659 100644
> --- a/drivers/hwmon/occ/p9_sbe.c
> +++ b/drivers/hwmon/occ/p9_sbe.c
> @@ -14,6 +14,8 @@
>
>  #include "common.h"
>
> +#define OCC_CHECKSUM_RETRIES   3
> +
>  struct p9_sbe_occ {
>         struct occ occ;
>         bool sbe_error;
> @@ -83,17 +85,22 @@ static int p9_sbe_occ_send_cmd(struct occ *occ, u8 *cmd, size_t len)
>         struct occ_response *resp = &occ->resp;
>         struct p9_sbe_occ *ctx = to_p9_sbe_occ(occ);
>         size_t resp_len = sizeof(*resp);
> +       int i;
>         int rc;
>
> -       rc = fsi_occ_submit(ctx->sbe, cmd, len, resp, &resp_len);
> -       if (rc < 0) {
> +       for (i = 0; i < OCC_CHECKSUM_RETRIES; ++i) {
> +               rc = fsi_occ_submit(ctx->sbe, cmd, len, resp, &resp_len);
> +               if (rc >= 0)
> +                       break;
>                 if (resp_len) {
>                         if (p9_sbe_occ_save_ffdc(ctx, resp, resp_len))
>                                 sysfs_notify(&occ->bus_dev->kobj, NULL,
>                                              bin_attr_ffdc.attr.name);
> -               }
>
> -               return rc;
> +                       return rc;
> +               }
> +               if (rc != -EBADE)
> +                       return rc;

Future you might appreciate a comment above the EBADE check clarifying
why that error is being special cased.

>         }
>
>         switch (resp->return_status) {
> --
> 2.27.0
>