linux-kernel - Re: [v2,02/10] i2c-i801: Move hostcfg set/reset to i801

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Message-ID: <575A99DA.8080308@acm.org>
Date:	Fri, 10 Jun 2016 05:43:38 -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: [v2,02/10] i2c-i801: Move hostcfg set/reset to i801_access()

On 06/09/2016 04:39 AM, Benjamin Tissoires wrote:
> On May 29 2016 or thereabouts, Corey Minyard wrote:
>> From: Corey Minyard <cminyard@...sta.com>
>>
>> The HSTCFG register save/restore was done in i2c_block_transaction,
>> but all the checks were already done in i801_access, so move it into
>> those checks.
>>
>> This results in a small savings of code, and moves some special
>> handing for I2C transactions into code that is already handling
>> special things for I2C transactions.
>>
>> Signed-off-by: Corey Minyard <cminyard@...sta.com>
>> ---
>>   drivers/i2c/busses/i2c-i801.c | 41 +++++++++++++++++++----------------------
>>   1 file changed, 19 insertions(+), 22 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
>> index 818c0c8..205f9d0 100644
>> --- a/drivers/i2c/busses/i2c-i801.c
>> +++ b/drivers/i2c/busses/i2c-i801.c
>> @@ -661,20 +661,6 @@ static int i801_block_transaction(struct i801_priv *priv,
>>   				  int command, int hwpec)
>>   {
>>   	int result = 0;
>> -	unsigned char hostc;
>> -
>> -	if (command == I2C_SMBUS_I2C_BLOCK_DATA) {
>> -		if (read_write == I2C_SMBUS_WRITE) {
>> -			/* set I2C_EN bit in configuration register */
>> -			pci_read_config_byte(priv->pci_dev, SMBHSTCFG, &hostc);
>> -			pci_write_config_byte(priv->pci_dev, SMBHSTCFG,
>> -					      hostc | SMBHSTCFG_I2C_EN);
>> -		} else if (!(priv->features & FEATURE_I2C_BLOCK_READ)) {
>> -			dev_err(&priv->pci_dev->dev,
>> -				"I2C block read is unsupported!\n");
>> -			return -EOPNOTSUPP;
>> -		}
>> -	}
>>   
>>   	if (read_write == I2C_SMBUS_WRITE
>>   	 || command == I2C_SMBUS_I2C_BLOCK_DATA) {
>> @@ -699,11 +685,6 @@ static int i801_block_transaction(struct i801_priv *priv,
>>   							     read_write,
>>   							     command);
>>   
>> -	if (command == I2C_SMBUS_I2C_BLOCK_DATA
>> -	 && read_write == I2C_SMBUS_WRITE) {
>> -		/* restore saved configuration register value */
>> -		pci_write_config_byte(priv->pci_dev, SMBHSTCFG, hostc);
>> -	}
>>   	return result;
>>   }
>>   
>> @@ -715,6 +696,7 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr,
>>   	int hwpec;
>>   	int block = 0;
>>   	int ret = 0, xact = 0;
>> +	int hostc = -1;
>>   	struct i801_priv *priv = i2c_get_adapdata(adap);
>>   
>>   	pm_runtime_get_sync(&priv->pci_dev->dev);
>> @@ -764,12 +746,24 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr,
>>   		/* NB: page 240 of ICH5 datasheet shows that the R/#W
>>   		 * bit should be cleared here, even when reading */
>>   		outb_p((addr & 0x7f) << 1, SMBHSTADD(priv));
>> -		if (read_write == I2C_SMBUS_READ) {
>> +		if (read_write == I2C_SMBUS_WRITE) {
>> +			unsigned char thostc;
>> +
>> +			outb_p(command, SMBHSTCMD(priv));
>> +			/* set I2C_EN bit in configuration register */
>> +			pci_read_config_byte(priv->pci_dev, SMBHSTCFG, &thostc);
>> +			pci_write_config_byte(priv->pci_dev, SMBHSTCFG,
>> +					      thostc | SMBHSTCFG_I2C_EN);
>> +			hostc = thostc;
>> +		} else if (!(priv->features & FEATURE_I2C_BLOCK_READ)) {
> nitpick: I'd prefer seeing:
> if (write) {
>    foo
> } else {
>    if (!FEATURE_I2C_BLOCK_READ) {
>      goto out
>    }
>    bar
> }
>
> It's equivalent but I feel like it's easier to understand.

First, thanks for all the reviews.  I really appreciate it.

On this particular change, it's moved from another location unchanged,
and it follows the style of the rest of the file.  I personally think 
it's better
to leave it like it is.

-corey

> Other than that, no strong opinion on the patch itself, but it's correct
> (the code path stays the same):
> Reviewed-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
>
> Cheers,
> Benjamin
>
>> +			dev_err(&priv->pci_dev->dev,
>> +				"I2C block read is unsupported!\n");
>> +			ret = -EOPNOTSUPP;
>> +			goto out;
>> +		} else
>>   			/* NB: page 240 of ICH5 datasheet also shows
>>   			 * that DATA1 is the cmd field when reading */
>>   			outb_p(command, SMBHSTDAT1(priv));
>> -		} else
>> -			outb_p(command, SMBHSTCMD(priv));
>>   		block = 1;
>>   		break;
>>   	default:
>> @@ -798,6 +792,9 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr,
>>   		outb_p(inb_p(SMBAUXCTL(priv)) &
>>   		       ~(SMBAUXCTL_CRC | SMBAUXCTL_E32B), SMBAUXCTL(priv));
>>   
>> +	if (hostc >= 0)
>> +		pci_write_config_byte(priv->pci_dev, SMBHSTCFG, hostc);
>> +
>>   	if (block)
>>   		goto out;
>>   	if (ret)