Re: [PATCH v4 2/3] i2c-piix4: Add support for multiplexed main adapter in SB800

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Sun, 2015-11-15 at 12:33 +0100, Christian Fetzer wrote:
> The SB800 chipset supports a multiplexed main SMBus controller with
> four ports. The multiplexed ports share the same SMBus address and
> register set. The port is selected by bits 2:1 of the smb_en register
> (0x2C).
> 
> Only one port can be active at any point in time therefore a mutex is
> needed in order to synchronize access.
> 
> Additionally, the commit avoids requesting and releasing the SMBus
> base
> address index region on every multiplexed transfer by moving the
> request_region call into piix4_probe.
> 
> Tested on HP ProLiant MicroServer G7 N54L (where this patch adds
> support to access sensor data from the w83795adg).

One nitpick below.

> 
> +/*
> + * Handles access to multiple SMBus ports on the SB800.
> 

> + * The port is selected by bits 2:1 of the smb_en register (0x2C).

(1)

> + * Returns negative errno on error.
> + *
> + * Note: The selected port must be returned to the initial selection
> to avoid
> + * problems on certain systems.
> + */
> +static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
> +		 unsigned short flags, char read_write,
> +		 u8 command, int size, union i2c_smbus_data *data)
> +{
> +	struct i2c_piix4_adapdata *adapdata =
> i2c_get_adapdata(adap);
> +	u8 smba_en_lo, smb_en = 0x2c;
> +	u8 port;
> +	int retval;
> +
> +	mutex_lock(adapdata->mutex);
> +
> +	outb_p(smb_en, SB800_PIIX4_SMB_IDX);
> +	smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
> +
> +	port = adapdata->port;
> +	if ((smba_en_lo & 6) != (port << 1))

I think it would be nice to have a definition for magic number along
with (1).

/* The port is selected by bits 2:1 of the smb_en register (0x2C) */
#define SB800_PIIX4_PORT_IDX_MASK 0x06

> +		outb_p((smba_en_lo & ~6) | (port << 1),
> +		       SB800_PIIX4_SMB_IDX + 1);
> +
> +	retval = piix4_access(adap, addr, flags, read_write,
> +			      command, size, data);
> +
> +	outb_p(smba_en_lo, SB800_PIIX4_SMB_IDX + 1);
> +
> +	mutex_unlock(adapdata->mutex);
> +
> +	return retval;
> +}
> +
>  static u32 piix4_func(struct i2c_adapter *adapter)
>  {
>  	return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
> @@ -539,6 +581,11 @@ static const struct i2c_algorithm
> smbus_algorithm = {
>  	.functionality	= piix4_func,
>  };
>  
> +static const struct i2c_algorithm piix4_smbus_algorithm_sb800 = {
> +	.smbus_xfer	= piix4_access_sb800,
> +	.functionality	= piix4_func,
> +};
> +
>  static const struct pci_device_id piix4_ids[] = {
>  	{ PCI_DEVICE(PCI_VENDOR_ID_INTEL,
> PCI_DEVICE_ID_INTEL_82371AB_3) },
>  	{ PCI_DEVICE(PCI_VENDOR_ID_INTEL,
> PCI_DEVICE_ID_INTEL_82443MX_3) },
> @@ -614,6 +661,53 @@ static int piix4_add_adapter(struct pci_dev
> *dev, unsigned short smba,
>  	return 0;
>  }
>  
> +static int piix4_add_adapters_sb800(struct pci_dev *dev, unsigned
> short smba)
> +{
> +	struct mutex *mutex;
> +	struct i2c_piix4_adapdata *adapdata;
> +	int port;
> +	int retval;
> +
> +	mutex = kzalloc(sizeof(*mutex), GFP_KERNEL);
> +	if (mutex == NULL)
> +		return -ENOMEM;
> +
> +	mutex_init(mutex);
> +
> +	for (port = 0; port < PIIX4_MAX_ADAPTERS; port++) {
> +		retval = piix4_add_adapter(dev, smba,
> +					   &piix4_main_adapters[port
> ]);
> +		if (retval < 0)
> +			goto error;
> +
> +		piix4_main_adapters[port]->algo =
> &piix4_smbus_algorithm_sb800;
> +
> +		adapdata =
> i2c_get_adapdata(piix4_main_adapters[port]);
> +		adapdata->sb800_main = true;
> +		adapdata->port = port;
> +		adapdata->mutex = mutex;
> +	}
> +
> +	return retval;
> +
> +error:
> +	dev_err(&dev->dev,
> +		"Error setting up SB800 adapters.
> Unregistering!\n");
> +	while (--port >= 0) {
> +		adapdata =
> i2c_get_adapdata(piix4_main_adapters[port]);
> +		if (adapdata->smba) {
> +			i2c_del_adapter(piix4_main_adapters[port]);
> +			kfree(adapdata);
> +			kfree(piix4_main_adapters[port]);
> +			piix4_main_adapters[port] = NULL;
> +		}
> +	}
> +
> +	kfree(mutex);
> +
> +	return retval;
> +}
> +
>  static int piix4_probe(struct pci_dev *dev, const struct
> pci_device_id *id)
>  {
>  	int retval;
> @@ -621,20 +715,41 @@ static int piix4_probe(struct pci_dev *dev,
> const struct pci_device_id *id)
>  	if ((dev->vendor == PCI_VENDOR_ID_ATI &&
>  	     dev->device == PCI_DEVICE_ID_ATI_SBX00_SMBUS &&
>  	     dev->revision >= 0x40) ||
> -	    dev->vendor == PCI_VENDOR_ID_AMD)
> +	    dev->vendor == PCI_VENDOR_ID_AMD) {
> +		if (!request_region(SB800_PIIX4_SMB_IDX, 2,
> "smba_idx")) {
> +			dev_err(&dev->dev,
> +			"SMBus base address index region 0x%x
> already in use!\n",
> +			SB800_PIIX4_SMB_IDX);
> +			return -EBUSY;
> +		}
> +
>  		/* base address location etc changed in SB800 */
>  		retval = piix4_setup_sb800(dev, id, 0);
> -	else
> -		retval = piix4_setup(dev, id);
> +		if (retval < 0) {
> +			release_region(SB800_PIIX4_SMB_IDX, 2);
> +			return retval;
> +		}
>  
> -	/* If no main SMBus found, give up */
> -	if (retval < 0)
> -		return retval;
> +		/*
> +		 * Try to register multiplexed main SMBus adapter,
> +		 * give up if we can't
> +		 */
> +		retval = piix4_add_adapters_sb800(dev, retval);
> +		if (retval < 0) {
> +			release_region(SB800_PIIX4_SMB_IDX, 2);
> +			return retval;
> +		}
> +	} else {
> +		retval = piix4_setup(dev, id);
> +		if (retval < 0)
> +			return retval;
>  
> -	/* Try to register main SMBus adapter, give up if we can't
> */
> -	retval = piix4_add_adapter(dev, retval,
> &piix4_main_adapters[0]);
> -	if (retval < 0)
> -		return retval;
> +		/* Try to register main SMBus adapter, give up if we
> can't */
> +		retval = piix4_add_adapter(dev, retval,
> +					   &piix4_main_adapters[0]);
> +		if (retval < 0)
> +			return retval;
> +	}
>  
>  	/* Check for auxiliary SMBus on some AMD chipsets */
>  	retval = -ENODEV;
> @@ -669,7 +784,13 @@ static void piix4_adap_remove(struct i2c_adapter
> *adap)
>  
>  	if (adapdata->smba) {
>  		i2c_del_adapter(adap);
> -		release_region(adapdata->smba, SMBIOSIZE);
> +		if (adapdata->port == 0) {
> +			release_region(adapdata->smba, SMBIOSIZE);
> +			if (adapdata->sb800_main) {
> +				kfree(adapdata->mutex);
> +				release_region(SB800_PIIX4_SMB_IDX,
> 2);
> +			}
> +		}
>  		kfree(adapdata);
>  		kfree(adap);
>  	}

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy