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Message-ID: <575A9FF8.1070706@acm.org>
Date: Fri, 10 Jun 2016 06:09:44 -0500
From: Corey Minyard <minyard@....org>
To: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc: Jean Delvare <jdelvare@...e.com>, linux-i2c@...r.kernel.org,
linux-kernel@...r.kernel.org, Corey Minyard <cminyard@...sta.com>
Subject: Re: [v2,05/10] i2c-i801: Consolidate calls to i801_check_post
On 06/09/2016 05:03 AM, Benjamin Tissoires wrote:
> On May 29 2016 or thereabouts, Corey Minyard wrote:
>> From: Corey Minyard <cminyard@...sta.com>
>>
>> This was almost always called at the end of the transaction. The
>> only time it wasn't called was when a protocol violation occurred,
>> and the error reporting was inconsistent there.
>>
>> So have the transaction functions return positive status or a
>> negative error if they detect an issue. If a protocol violation
>> does occur, always do a kill operation on the bus instead of just
>> trying to finish the operation. If there was a hardware issue,
>> the code that was there to terminate the transaction could loop
>> forever, and the kill seems more appropriate if something goes
>> grossly wrong.
>>
>> Signed-off-by: Corey Minyard <cminyard@...sta.com>
>> ---
> I *think* the patch is OK. I have a few comments.
>
>> drivers/i2c/busses/i2c-i801.c | 51 +++++++++++++++++++++----------------------
>> 1 file changed, 25 insertions(+), 26 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
>> index 8794e70..56db310 100644
>> --- a/drivers/i2c/busses/i2c-i801.c
>> +++ b/drivers/i2c/busses/i2c-i801.c
>> @@ -317,7 +317,13 @@ static int i801_check_post(struct i801_priv *priv, int status)
>> * DEV_ERR.
>> */
>> if (unlikely(status < 0)) {
>> - dev_err(&priv->pci_dev->dev, "Transaction timeout\n");
>> + result = status;
>> + if (status == -EPROTO)
>> + dev_err(&priv->pci_dev->dev,
>> + "Illegal SMBus block read size %d\n",
>> + priv->len);
> Not sure this is a good idea to map -EPROTO to "Illegal SMBus block read
> size". True, it looks like it can only happens this way, but I would
> rather see it mapped to "Protocol Error". Given that Protocol Error is
> not very interesting in itself, I'd rather keep the error messages in
> the callers only (except for ETIMEOUT where you can output an error
> message).
That would mean you would have exactly the same error print in
two (well, three if you count a future patch) different locations in the
code. I moved it here to avoid that issue. I agree that "Protocol
Error" is not that specific, and I don't see a clean way to communicate
this information. So I think you are right.
>> + else
>> + dev_err(&priv->pci_dev->dev, "Transaction timeout\n");
>> /* try to stop the current command */
>> dev_dbg(&priv->pci_dev->dev, "Terminating the current operation\n");
>> outb_p(inb_p(SMBHSTCNT(priv)) | SMBHSTCNT_KILL,
>> @@ -333,7 +339,7 @@ static int i801_check_post(struct i801_priv *priv, int status)
>> dev_err(&priv->pci_dev->dev,
>> "Failed terminating the transaction\n");
>> outb_p(STATUS_FLAGS, SMBHSTSTS(priv));
>> - return -ETIMEDOUT;
>> + return result;
>> }
>>
>> if (status & SMBHSTSTS_FAILED) {
>> @@ -414,15 +420,14 @@ static int i801_transaction(struct i801_priv *priv, int xact)
>> "Timeout waiting for interrupt!\n");
> Here, the code already dev_warn the timeout and later i801_check_post
> will dev_err the timeout too. That's one too much IMO :)
Indeed, I didn't notice that.
>
>> }
>> priv->status = 0;
>> - return i801_check_post(priv, status);
>> + return status;
>> }
>>
>> /* the current contents of SMBHSTCNT can be overwritten, since PEC,
>> * SMBSCMD are passed in xact */
>> outb_p(xact | SMBHSTCNT_START, SMBHSTCNT(priv));
>>
>> - status = i801_wait_intr(priv);
>> - return i801_check_post(priv, status);
>> + return i801_wait_intr(priv);
>> }
>>
>> static int i801_block_transaction_by_block(struct i801_priv *priv,
>> @@ -444,11 +449,11 @@ static int i801_block_transaction_by_block(struct i801_priv *priv,
>>
>> status = i801_transaction(priv, I801_BLOCK_DATA |
>> (hwpec ? SMBHSTCNT_PEC_EN : 0));
>> - if (status)
>> + if (status < 0 || status & STATUS_ERROR_FLAGS)
>> return status;
>>
>> if (read_write == I2C_SMBUS_READ) {
>> - len = inb_p(SMBHSTDAT0(priv));
>> + len = priv->len = inb_p(SMBHSTDAT0(priv));
>> if (len < 1 || len > I2C_SMBUS_BLOCK_MAX)
>> return -EPROTO;
>>
>> @@ -456,7 +461,7 @@ static int i801_block_transaction_by_block(struct i801_priv *priv,
>> for (i = 0; i < len; i++)
>> data->block[i + 1] = inb_p(SMBBLKDAT(priv));
>> }
>> - return 0;
>> + return status;
>> }
>>
>> static void i801_isr_byte_done(struct i801_priv *priv)
>> @@ -590,7 +595,7 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
>> "Timeout waiting for interrupt!\n");
>> }
>> priv->status = 0;
>> - return i801_check_post(priv, status);
>> + return status;
>> }
>>
>> for (i = 1; i <= len; i++) {
>> @@ -604,24 +609,14 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
>>
>> status = i801_wait_byte_done(priv);
>> if (status)
>> - goto exit;
>> + return status;
>>
>> if (i == 1 && read_write == I2C_SMBUS_READ
>> && command != I2C_SMBUS_I2C_BLOCK_DATA) {
>> - len = inb_p(SMBHSTDAT0(priv));
>> - if (len < 1 || len > I2C_SMBUS_BLOCK_MAX) {
>> - dev_err(&priv->pci_dev->dev,
>> - "Illegal SMBus block read size %d\n",
>> - len);
>> - /* Recover */
>> - while (inb_p(SMBHSTSTS(priv)) &
>> - SMBHSTSTS_HOST_BUSY)
>> - outb_p(SMBHSTSTS_BYTE_DONE,
>> - SMBHSTSTS(priv));
>> - outb_p(SMBHSTSTS_INTR, SMBHSTSTS(priv));
>> + priv->len = inb_p(SMBHSTDAT0(priv));
>> + if (priv->len < 1 || priv->len > I2C_SMBUS_BLOCK_MAX)
>> return -EPROTO;
>> - }
>> - data->block[0] = len;
>> + data->block[0] = len = priv->len;
> Not entirely sure why the priv->len changes are interleaved in this
> patch. I might be missing something, but it looks like it should not be
> there or in a separate patch.
This was so the code reporting the error in the check_post function could
print out the length value. If I move the logs to where the error is
detected,
the priv->len setting here will no longer be necessary.
Thanks,
-corey
> Cheers,
> Benjamin
>
>> }
>>
>> /* Retrieve/store value in SMBBLKDAT */
>> @@ -634,9 +629,7 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
>> outb_p(SMBHSTSTS_BYTE_DONE, SMBHSTSTS(priv));
>> }
>>
>> - status = i801_wait_intr(priv);
>> -exit:
>> - return i801_check_post(priv, status);
>> + return i801_wait_intr(priv);
>> }
>>
>> static int i801_set_block_buffer_mode(struct i801_priv *priv)
>> @@ -791,6 +784,12 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr,
>> else
>> ret = i801_transaction(priv, xact);
>>
>> + /*
>> + * ret can be status if positive or an error if negative. Let
>> + * the post check handle it.
>> + */
>> + ret = i801_check_post(priv, ret);
>> +
>> if (hostc >= 0)
>> pci_write_config_byte(priv->pci_dev, SMBHSTCFG, hostc);
>>
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