linux-kernel - Re: [2/3] i2c: piix4: fix number of ports on Family 16h Model 30h

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Date:   Sun, 28 Jan 2018 21:58:24 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Andrew Cooks <andrew.cooks@...ngear.com>
Cc:     Jean Delvare <jdelvare@...e.com>, Wolfram Sang <wsa@...-dreams.de>,
        "open list:I2C/SMBUS CONTROLLER DRIVERS FOR PC" 
        <linux-i2c@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [2/3] i2c: piix4: fix number of ports on Family 16h Model 30h

On Mon, Jan 29, 2018 at 01:54:19PM +1000, Andrew Cooks wrote:
> Prevent bus timeouts and resets on Family 16h Model 30h), by not
> probing reserved Ports 3 and 4.
> 
> According to the AMD BIOS and Kernel Developer's Guides (BKDG), Port 3
> and Port 4 are reserved on the following devices:
>  - Family 15h Model 60h-6Fh,
>  - Family 15h Model 70h-7Fh,
>  - Family 16h Models 30h-3Fh,
> 
> Signed-off-by: Andrew Cooks <andrew.cooks@...ngear.com>
> ---
>  drivers/i2c/busses/i2c-piix4.c | 31 ++++++++++++++++++++++---------
>  1 file changed, 22 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
> index 89692f4..9763241 100644
> --- a/drivers/i2c/busses/i2c-piix4.c
> +++ b/drivers/i2c/busses/i2c-piix4.c
> @@ -82,6 +82,13 @@
>  /* Multi-port constants */
>  #define PIIX4_MAX_ADAPTERS 4
>  
> +/*
> + * Main adapter port count. At least one (Port 0) plus up to 3 additional
> + * (Ports 2-4)
> + */

This is a bit misleading. Which adapter has only one port ?

> +#define SB800_MAIN_PORTS 4
> +#define HUDSON2_MAIN_PORTS 2 /* HUDSON2, reserves Port 3 and Port 4 */
> +
A tab between define and value might be helpful. 
Not sure though why both PIIX4_MAX_ADAPTERS and SB800_MAIN_PORTS
are needed.

>  /* SB800 constants */
>  #define SB800_PIIX4_SMB_IDX		0xcd6
>  
> @@ -800,6 +807,7 @@ MODULE_DEVICE_TABLE (pci, piix4_ids);
>  
>  static struct i2c_adapter *piix4_main_adapters[PIIX4_MAX_ADAPTERS];
>  static struct i2c_adapter *piix4_aux_adapter;
> +static int piix4_adapter_count;

This variable is never set, only decreased.

>  
>  static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
>  			     bool sb800_main, u8 port, bool notify_imc,
> @@ -856,10 +864,17 @@ static int piix4_add_adapters_sb800(struct pci_dev *dev, unsigned short smba,
>  				    bool notify_imc)
>  {
>  	struct i2c_piix4_adapdata *adapdata;
> -	int port;
> +	int port, port_count;
>  	int retval;
>  
> -	for (port = 0; port < PIIX4_MAX_ADAPTERS; port++) {
> +	if (dev->device == PCI_DEVICE_ID_AMD_HUDSON2_SMBUS ||
> +	    dev->device == PCI_DEVICE_ID_AMD_KERNCZ_SMBUS) {
> +		port_count = HUDSON2_MAIN_PORTS;
> +	} else {
> +		port_count = SB800_MAIN_PORTS;
> +	}
> +
> +	for (port = 0; port < port_count; port++) {
>  		retval = piix4_add_adapter(dev, smba, true, port, notify_imc,
>  					   piix4_main_port_names_sb800[port],
>  					   &piix4_main_adapters[port]);
> @@ -872,7 +887,7 @@ static int piix4_add_adapters_sb800(struct pci_dev *dev, unsigned short smba,
>  error:
>  	dev_err(&dev->dev,
>  		"Error setting up SB800 adapters. Unregistering!\n");
> -	while (--port >= 0) {
> +	while (--piix4_adapter_count >= 0) {

This is wrong, even if piix4_adapter_count was initialized.

>  		adapdata = i2c_get_adapdata(piix4_main_adapters[port]);
>  		if (adapdata->smba) {
>  			i2c_del_adapter(piix4_main_adapters[port]);
> @@ -993,12 +1008,10 @@ static void piix4_adap_remove(struct i2c_adapter *adap)
>  
>  static void piix4_remove(struct pci_dev *dev)
>  {
> -	int port = PIIX4_MAX_ADAPTERS;

A one line change would do it just as well.
	int port = piix4_adapter_count;

> -
> -	while (--port >= 0) {
> -		if (piix4_main_adapters[port]) {
> -			piix4_adap_remove(piix4_main_adapters[port]);
> -			piix4_main_adapters[port] = NULL;
> +	while (--piix4_adapter_count >= 0) {
> +		if (piix4_main_adapters[piix4_adapter_count]) {
> +			piix4_adap_remove(piix4_main_adapters[piix4_adapter_count]);
> +			piix4_main_adapters[piix4_adapter_count] = NULL;
>  		}
>  	}
>