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

From: Benjamin Tissoires
Date: Thu Jul 28 2016 - 05:45:18 EST

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Hi Jean,

On Jul 18 2016 or thereabouts, Jean Delvare wrote:
> 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?

I have tested the T440, t450 and t460 (3 different generation of Intel
processor), and none seems to be working. The Synaptics touchpad used is
mostly the same, so maybe that's a device issue.

>
> > Tested-by: Andrew Duggan <aduggan@xxxxxxxxxxxxx>
> > Acked-by: Wolfram Sang <wsa@xxxxxxxxxxxxx>
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
> > ---
> > 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.

Well, yes, I suppose too :)

I am about to send a series to address all of your remarks. Thanks for
the review!

Cheers,
Benjamin

>
> > +
> > + 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

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