Re: [PATCH v9 1/2] i2c: i801: add support of Host Notify

[Jean Delvare <jdelvare@suse.de>]

Hi Benjamin,

Once again, sorry for the late review.

On Fri, 24 Jun 2016 16:39:49 +0200, Benjamin Tissoires wrote:
> The i801 chip can handle the Host Notify feature since ICH 3 as mentioned
> in http://www.intel.com/content/dam/doc/datasheet/82801ca-io-controller-hub-3-datasheet.pdf
> 
> Enable the functionality unconditionally and propagate the alert
> on each notification.
> 
> With a T440s and a Synaptics touchpad that implements Host Notify, the
> payload data is always 0x0000, so I am not sure if the device actually
> sends the payload or if there is a problem regarding the implementation.

Out of curiosity, does it work on at least one machine?

> Tested-by: Andrew Duggan <aduggan@synaptics.com>
> Acked-by: Wolfram Sang <wsa@the-dreams.de>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> ---
> changes in v2:
> - removed the description of the Slave functionality support in the chip table
>   (the table shows what is supported, not what the hardware is capable of)
> - use i2c-smbus to forward the notification
> - remove the fifo, and directly retrieve the address and payload in the worker
> - do not check for Host Notification is the feature is not enabled
> - use inw_p() to read the payload instead of 2 inb_p() calls
> - add /* fall-through */ comment
> - unconditionally enable Host Notify if the hardware supports it (can be
>   disabled by the user)
> 
> no changes in v3
> 
> changes in v4:
> - make use of the new API -> no more worker spawning here
> - solved a race between the access of the Host Notify registers and the actual
>   I2C transfers.
> 
> changes in v5:
> - added SKL Host Notify support
> 
> changes in v6:
> - select I2C_SMBUS in Kconfig to prevent an undefined reference when I2C_I801
>   is set to 'Y' while I2C_SMBUS is set to 'M'
> 
> no changes in v7
> 
> changes in v8:
> - reapplied after http://patchwork.ozlabs.org/patch/632768/ and merged the
>   conflict (minor conflict in the struct i801_priv).
> - removed the .resume hook as upstream changed suspend/resume hooks and there
>   is no need in the end to re-enable host notify on resume (tested on Lenovo
>   t440 and t450).
> - kept Wolfram's Acked-by as the changes were minor
> 
> changes in v9:
> - re-add the .resume hook. Looks like the Lenovo T440 sometimes forget to
>   re-enable Host Notify on resume, so better have it reset for everybody
> 
>  drivers/i2c/busses/Kconfig    |  1 +
>  drivers/i2c/busses/i2c-i801.c | 88 +++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 86 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index efa3d9b..b4b6cb0 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -91,6 +91,7 @@ config I2C_I801
>  	tristate "Intel 82801 (ICH/PCH)"
>  	depends on PCI
>  	select CHECK_SIGNATURE if X86 && DMI
> +	select I2C_SMBUS
>  	help
>  	  If you say yes to this option, support will be included for the Intel
>  	  801 family of mainboard I2C interfaces.  Specifically, the following
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index b436963..312caed 100644
> --- a/drivers/i2c/busses/i2c-i801.c
> +++ b/drivers/i2c/busses/i2c-i801.c
> @@ -72,6 +72,7 @@
>   * Block process call transaction	no
>   * I2C block read transaction		yes (doesn't use the block buffer)
>   * Slave mode				no
> + * SMBus Host Notify			yes
>   * Interrupt processing			yes
>   *
>   * See the file Documentation/i2c/busses/i2c-i801 for details.
> @@ -86,6 +87,7 @@
>  #include <linux/ioport.h>
>  #include <linux/init.h>
>  #include <linux/i2c.h>
> +#include <linux/i2c-smbus.h>
>  #include <linux/acpi.h>
>  #include <linux/io.h>
>  #include <linux/dmi.h>
> @@ -113,6 +115,10 @@
>  #define SMBPEC(p)	(8 + (p)->smba)		/* ICH3 and later */
>  #define SMBAUXSTS(p)	(12 + (p)->smba)	/* ICH4 and later */
>  #define SMBAUXCTL(p)	(13 + (p)->smba)	/* ICH4 and later */
> +#define SMBSLVSTS(p)	(16 + (p)->smba)	/* ICH3 and later */
> +#define SMBSLVCMD(p)	(17 + (p)->smba)	/* ICH3 and later */
> +#define SMBNTFDADD(p)	(20 + (p)->smba)	/* ICH3 and later */
> +#define SMBNTFDDAT(p)	(22 + (p)->smba)	/* ICH3 and later */
>  
>  /* PCI Address Constants */
>  #define SMBBAR		4
> @@ -177,6 +183,12 @@
>  #define SMBHSTSTS_INTR		0x02
>  #define SMBHSTSTS_HOST_BUSY	0x01
>  
> +/* Host Notify Status registers bits */
> +#define SMBSLVSTS_HST_NTFY_STS	1
> +
> +/* Host Notify Command registers bits */
> +#define SMBSLVCMD_HST_NTFY_INTREN	0x01

"register" needs no "s" in these 2 comments. Also it would be nice to
stick to hexadecimal for consistency (I know it's not the case
elsewhere in the driver, but let's not add to it.)

> +
>  #define STATUS_ERROR_FLAGS	(SMBHSTSTS_FAILED | SMBHSTSTS_BUS_ERR | \
>  				 SMBHSTSTS_DEV_ERR)
>  
> @@ -252,13 +264,17 @@ struct i801_priv {
>  	 */
>  	bool acpi_reserved;
>  	struct mutex acpi_lock;
> +	struct smbus_host_notify *host_notify;
>  };
>  
> +#define SMBHSTNTFY_SIZE		8

This constant isn't used anywhere?

> +
>  #define FEATURE_SMBUS_PEC	(1 << 0)
>  #define FEATURE_BLOCK_BUFFER	(1 << 1)
>  #define FEATURE_BLOCK_PROC	(1 << 2)
>  #define FEATURE_I2C_BLOCK_READ	(1 << 3)
>  #define FEATURE_IRQ		(1 << 4)
> +#define FEATURE_HOST_NOTIFY	(1 << 5)
>  /* Not really a feature, but it's convenient to handle it as such */
>  #define FEATURE_IDF		(1 << 15)
>  #define FEATURE_TCO		(1 << 16)
> @@ -269,6 +285,7 @@ static const char *i801_feature_names[] = {
>  	"Block process call",
>  	"I2C block read",
>  	"Interrupt",
> +	"SMBus Host Notify",
>  };
>  
>  static unsigned int disable_features;
> @@ -277,7 +294,8 @@ MODULE_PARM_DESC(disable_features, "Disable selected driver features:\n"
>  	"\t\t  0x01  disable SMBus PEC\n"
>  	"\t\t  0x02  disable the block buffer\n"
>  	"\t\t  0x08  disable the I2C block read functionality\n"
> -	"\t\t  0x10  don't use interrupts ");
> +	"\t\t  0x10  don't use interrupts\n"
> +	"\t\t  0x20  disable SMBus Host Notify ");
>  
>  /* Make sure the SMBus host is ready to start transmitting.
>     Return 0 if it is, -EBUSY if it is not. */
> @@ -511,8 +529,23 @@ static void i801_isr_byte_done(struct i801_priv *priv)
>  	outb_p(SMBHSTSTS_BYTE_DONE, SMBHSTSTS(priv));
>  }
>  
> +static irqreturn_t i801_host_notify_isr(struct i801_priv *priv)
> +{
> +	unsigned short addr;
> +	unsigned int data;
> +
> +	addr = inb_p(SMBNTFDADD(priv)) >> 1;
> +	data = inw_p(SMBNTFDDAT(priv));

The ICH9 datasheet I'm looking at says the data is in 2 8-bit
registers. I wonder if a 16-bit read is OK an all chipsets. Well, if it
isn't we'll learn about it someday, I suppose.

> +
> +	i2c_handle_smbus_host_notify(priv->host_notify, addr, data);

This can fail, in theory. Maybe this should be handled?

> +
> +	/* clear Host Notify bit and return */
> +	outb_p(SMBSLVSTS_HST_NTFY_STS, SMBSLVSTS(priv));
> +	return IRQ_HANDLED;
> +}
> +
>  /*
> - * There are two kinds of interrupts:
> + * There are three kinds of interrupts:
>   *
>   * 1) i801 signals transaction completion with one of these interrupts:
>   *      INTR - Success
> @@ -524,6 +557,8 @@ static void i801_isr_byte_done(struct i801_priv *priv)
>   *
>   * 2) For byte-by-byte (I2C read/write) transactions, one BYTE_DONE interrupt
>   *    occurs for each byte of a byte-by-byte to prepare the next byte.
> + *
> + * 3) Host Notify interrupts
>   */
>  static irqreturn_t i801_isr(int irq, void *dev_id)
>  {
> @@ -536,6 +571,12 @@ static irqreturn_t i801_isr(int irq, void *dev_id)
>  	if (!(pcists & SMBPCISTS_INTS))
>  		return IRQ_NONE;
>  
> +	if (priv->features & FEATURE_HOST_NOTIFY) {
> +		status = inb_p(SMBSLVSTS(priv));
> +		if (status & SMBSLVSTS_HST_NTFY_STS)
> +			return i801_host_notify_isr(priv);
> +	}
> +
>  	status = inb_p(SMBHSTSTS(priv));
>  	if (status & SMBHSTSTS_BYTE_DONE)
>  		i801_isr_byte_done(priv);
> @@ -847,7 +888,28 @@ static u32 i801_func(struct i2c_adapter *adapter)
>  	       I2C_FUNC_SMBUS_BLOCK_DATA | I2C_FUNC_SMBUS_WRITE_I2C_BLOCK |
>  	       ((priv->features & FEATURE_SMBUS_PEC) ? I2C_FUNC_SMBUS_PEC : 0) |
>  	       ((priv->features & FEATURE_I2C_BLOCK_READ) ?
> -		I2C_FUNC_SMBUS_READ_I2C_BLOCK : 0);
> +		I2C_FUNC_SMBUS_READ_I2C_BLOCK : 0) |
> +	       ((priv->features & FEATURE_HOST_NOTIFY) ?
> +		I2C_FUNC_SMBUS_HOST_NOTIFY : 0);
> +}
> +
> +static int i801_enable_host_notify(struct i2c_adapter *adapter)
> +{
> +	struct i801_priv *priv = i2c_get_adapdata(adapter);
> +
> +	if (!(priv->features & FEATURE_HOST_NOTIFY))
> +		return -ENOTSUPP;

Why do you return an error here? This forces you to special-case it on
further error handling. You could simply return 0 instead, and save
some tests.

> +
> +	if (!priv->host_notify)
> +		priv->host_notify = i2c_setup_smbus_host_notify(adapter);
> +	if (!priv->host_notify)
> +		return -ENOMEM;

Minor optimization: if priv->host_notify was already set, the second
test is not needed.

> +
> +	outb_p(SMBSLVCMD_HST_NTFY_INTREN, SMBSLVCMD(priv));
> +	/* clear Host Notify bit to allow a new notification */
> +	outb_p(SMBSLVSTS_HST_NTFY_STS, SMBSLVSTS(priv));
> +
> +	return 0;
>  }
>  
>  static const struct i2c_algorithm smbus_algorithm = {
> @@ -1379,6 +1441,7 @@ static int i801_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  		priv->features |= FEATURE_SMBUS_PEC;
>  		priv->features |= FEATURE_BLOCK_BUFFER;
>  		priv->features |= FEATURE_TCO;
> +		priv->features |= FEATURE_HOST_NOTIFY;
>  		break;
>  
>  	case PCI_DEVICE_ID_INTEL_PATSBURG_SMBUS_IDF0:
> @@ -1398,6 +1461,8 @@ static int i801_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  		priv->features |= FEATURE_BLOCK_BUFFER;
>  		/* fall through */
>  	case PCI_DEVICE_ID_INTEL_82801CA_3:
> +		priv->features |= FEATURE_HOST_NOTIFY;
> +		/* fall through */
>  	case PCI_DEVICE_ID_INTEL_82801BA_2:
>  	case PCI_DEVICE_ID_INTEL_82801AB_3:
>  	case PCI_DEVICE_ID_INTEL_82801AA_3:
> @@ -1507,6 +1572,15 @@ static int i801_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  		return err;
>  	}
>  
> +	/*
> +	 * Enable Host Notify for chips that supports it.
> +	 * It is done after i2c_add_adapter() so that we are sure the work queue
> +	 * is not used if i2c_add_adapter() fails.
> +	 */
> +	err = i801_enable_host_notify(&priv->adapter);
> +	if (err && err != -ENOTSUPP)
> +		dev_warn(&dev->dev, "Unable to enable SMBus Host Notify\n");
> +
>  	i801_probe_optional_slaves(priv);
>  	/* We ignore errors - multiplexing is optional */
>  	i801_add_mux(priv);
> @@ -1553,6 +1627,14 @@ static int i801_suspend(struct device *dev)
>  
>  static int i801_resume(struct device *dev)
>  {
> +	struct pci_dev *pci_dev = to_pci_dev(dev);
> +	struct i801_priv *priv = pci_get_drvdata(pci_dev);
> +	int err;
> +
> +	err = i801_enable_host_notify(&priv->adapter);
> +	if (err && err != -ENOTSUPP)
> +		dev_warn(dev, "Unable to enable SMBus Host Notify\n");
> +
>  	return 0;
>  }
>  #endif


-- 
Jean Delvare
SUSE L3 Support