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

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Date:   Tue, 26 Apr 2022 10:46:06 -0500
From:   Eddie James <eajames@...ux.ibm.com>
To:     David Laight <David.Laight@...LAB.COM>,
        "'Guenter Roeck'" <linux@...ck-us.net>
Cc:     "linux-fsi@...ts.ozlabs.org" <linux-fsi@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "jdelvare@...e.com" <jdelvare@...e.com>,
        "joel@....id.au" <joel@....id.au>, "jk@...abs.org" <jk@...abs.org>,
        "alistair@...ple.id.au" <alistair@...ple.id.au>
Subject: Re: [PATCH 2/2] hwmon (occ): Retry for checksum failure


On 4/25/22 04:10, David Laight wrote:
> From: Guenter Roeck
>> Sent: 24 April 2022 18:18
>>
>> On Mon, Mar 21, 2022 at 10:31:12AM -0500, Eddie James 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>
>> I assume this will be applied together with patch 1 of the series.
>>
>> Acked-by: Guenter Roeck <linux@...ck-us.net>
>>
>> Guenter
>>
>>> ---
>>>   drivers/hwmon/occ/p9_sbe.c | 28 ++++++++++++++++++----------
>>>   1 file changed, 18 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/hwmon/occ/p9_sbe.c b/drivers/hwmon/occ/p9_sbe.c
>>> index 49b13cc01073..7f4c3f979c54 100644
>>> --- a/drivers/hwmon/occ/p9_sbe.c
>>> +++ b/drivers/hwmon/occ/p9_sbe.c
>>> @@ -84,17 +84,25 @@ static int p9_sbe_occ_send_cmd(struct occ *occ, u8 *cmd, size_t len)
>>>   	struct p9_sbe_occ *ctx = to_p9_sbe_occ(occ);
>>>   	size_t resp_len = sizeof(*resp);
>>>   	int rc;
>>> -
>>> -	rc = fsi_occ_submit(ctx->sbe, cmd, len, resp, &resp_len);
>>> -	if (rc < 0) {
>>> -		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);
>>> +	int tries = 0;
>>> +
>>> +	do {
> Why not use a for() loop?
>
>>> +		rc = fsi_occ_submit(ctx->sbe, cmd, len, resp, &resp_len);
>>> +		if (rc < 0) {
>>> +			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;
>>> +			} else if (rc != -EBADE) {
>>> +				return rc;
>>> +			}
> No need for else after return.
>
>>> +			/* retry twice for checksum failures */
>>> +		} else {
>>> +			break;
> I'd break on the success path after testing (rc >= 0).
> Saves a level of indent.
>
>>>   		}
>>> -
>>> -		return rc;
>>> -	}
>>> +	} while (++tries < 3);
>>>
>>>   	switch (resp->return_status) {
>>>   	case OCC_RESP_CMD_IN_PRG:
> Probably end up with something like:
> 	for (tries = 0; tries < 3; tries++) {
> 		rc = ...;
> 		if (rc >= 0)
> 			break;
> 		if (resp_len) {
> 			...
> 			return rc;
> 		}
> 		if (rc != -EBADE)
> 			return rc;
> 	}
>
> 	David


Thanks David, Ack.


>
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