linux-kernel - Re: [PATCH v4 3/9] i2c: piix4: Move port I/O region request/release code into functions

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Date:   Tue, 8 Feb 2022 09:15:21 -0600
From:   Terry Bowman <Terry.Bowman@....com>
To:     Jean Delvare <jdelvare@...e.de>
Cc:     linux@...ck-us.net, linux-watchdog@...r.kernel.org,
        jdelvare@...e.com, linux-i2c@...r.kernel.org, wsa@...nel.org,
        andy.shevchenko@...il.com, rafael.j.wysocki@...el.com,
        linux-kernel@...r.kernel.org, wim@...ux-watchdog.org,
        rrichter@....com, thomas.lendacky@....com, sudheesh.mavila@....com,
        Nehal-bakulchandra.Shah@....com, Basavaraj.Natikar@....com,
        Shyam-sundar.S-k@....com, Mario.Limonciello@....com
Subject: Re: [PATCH v4 3/9] i2c: piix4: Move port I/O region request/release
 code into functions

Hi Jean,

On 2/8/22 08:45, Jean Delvare wrote:
> Hi Terry,
> 
> On Sun, 30 Jan 2022 12:41:24 -0600, Terry Bowman wrote:
>> Move duplicated region request and release code into a function. Move is
>> in preparation for following MMIO changes.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@....com>
>> ---
>>  drivers/i2c/busses/i2c-piix4.c | 39 +++++++++++++++++++++++-----------
>>  1 file changed, 27 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
>> index 3ff68967034e..5a98970ac60a 100644
>> --- a/drivers/i2c/busses/i2c-piix4.c
>> +++ b/drivers/i2c/busses/i2c-piix4.c
>> @@ -165,6 +165,24 @@ struct i2c_piix4_adapdata {
>>  	u8 port;		/* Port number, shifted */
>>  };
>>  
>> +static int piix4_sb800_region_request(struct device *dev)
>> +{
>> +	if (!request_muxed_region(SB800_PIIX4_SMB_IDX, SB800_PIIX4_SMB_MAP_SIZE,
>> +				  "sb800_piix4_smb")) {
>> +		dev_err(dev,
>> +			"SMBus base address index region 0x%x already in use.\n",
>> +			SB800_PIIX4_SMB_IDX);
>> +		return -EBUSY;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static void piix4_sb800_region_release(struct device *dev)
>> +{
>> +	release_region(SB800_PIIX4_SMB_IDX, SB800_PIIX4_SMB_MAP_SIZE);
>> +}
>> +
>>  static int piix4_setup(struct pci_dev *PIIX4_dev,
>>  		       const struct pci_device_id *id)
>>  {
>> @@ -270,6 +288,7 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
>>  	unsigned short piix4_smba;
>>  	u8 smba_en_lo, smba_en_hi, smb_en, smb_en_status, port_sel;
>>  	u8 i2ccfg, i2ccfg_offset = 0x10;
>> +	int retval;
>>  
>>  	/* SB800 and later SMBus does not support forcing address */
>>  	if (force || force_addr) {
>> @@ -291,20 +310,16 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
>>  	else
>>  		smb_en = (aux) ? 0x28 : 0x2c;
>>  
>> -	if (!request_muxed_region(SB800_PIIX4_SMB_IDX, SB800_PIIX4_SMB_MAP_SIZE,
>> -				  "sb800_piix4_smb")) {
>> -		dev_err(&PIIX4_dev->dev,
>> -			"SMB base address index region 0x%x already in use.\n",
>> -			SB800_PIIX4_SMB_IDX);
>> -		return -EBUSY;
>> -	}
>> +	retval = piix4_sb800_region_request(&PIIX4_dev->dev);
>> +	if (retval)
>> +		return retval;
>>  
>>  	outb_p(smb_en, SB800_PIIX4_SMB_IDX);
>>  	smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
>>  	outb_p(smb_en + 1, SB800_PIIX4_SMB_IDX);
>>  	smba_en_hi = inb_p(SB800_PIIX4_SMB_IDX + 1);
>>  
>> -	release_region(SB800_PIIX4_SMB_IDX, SB800_PIIX4_SMB_MAP_SIZE);
>> +	piix4_sb800_region_release(&PIIX4_dev->dev);
>>  
>>  	if (!smb_en) {
>>  		smb_en_status = smba_en_lo & 0x10;
>> @@ -685,9 +700,9 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
>>  	u8 port;
>>  	int retval;
>>  
>> -	if (!request_muxed_region(SB800_PIIX4_SMB_IDX, SB800_PIIX4_SMB_MAP_SIZE,
>> -				  "sb800_piix4_smb"))
>> -		return -EBUSY;
>> +	retval = piix4_sb800_region_request(&adap->dev);
>> +	if (retval)
>> +		return retval;
>>  
>>  	/* Request the SMBUS semaphore, avoid conflicts with the IMC */
>>  	smbslvcnt  = inb_p(SMBSLVCNT);
>> @@ -762,7 +777,7 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
>>  		piix4_imc_wakeup();
>>  
>>  release:
>> -	release_region(SB800_PIIX4_SMB_IDX, SB800_PIIX4_SMB_MAP_SIZE);
>> +	piix4_sb800_region_release(&adap->dev);
>>  	return retval;
>>  }
>>  
> 
> There's a third occurrence of request_muxed_region(SB800_PIIX4_SMB_IDX,
> ...) / release_region(SB800_PIIX4_SMB_IDX, ...) in function
> piix4_setup_sb800. Any reason why you don't make use of the new helper
> functions there as well?
> 

I didn't update the other occurrence because it was outside the codepath
for the device we are addressing. At the time I wanted to minimize changes
particularly for other devices.

> OK, I see that this part of the code is specific to the original (ATI)
> SB800, so it can't use MMIO, therefore you don't *have* to call the
> helper functions. But for consistency, wouldn't it still make sense to
> use them?
> 

Yes, it would be more consistent if it used the helper function. 

Regards,
Terry