After a suspend / resume cycle we possibly need to reapply chip registers
settings that we had set or fixed in a probe path, since they might have
been reset to default values or set incorrectly by a BIOS again.

Tested on a Gigabyte M720-US3 board, which requires routing internal VCCH5V
to in7 (and had it wrong again on resume from S3).

Signed-off-by: Maciej S. Szmigiero <m...@maciej.szmigiero.name>
---
Changes from v1: Move code of common probe / resume steps to new functions
so we don't need to make large parts of probe function conditional on a
newly added 'resume' parameter.

Changes from v2: Code move of common probe / resume steps to new functions
and actual resume functionality split into two, separate patches.

Changed message level about VCCH5V being routed to in7 again on resume to
debug.

Added a "need_in7_reroute" flag and made VCCH5V to in7 rerouting on resume
explicitly conditional on it.

Didn't finally add check for enable_pwm_interface being set before calling
it87_check_pwm() in the resume function since this variable is it87_probe()
function local and so adding this check would require adding it to device
instance structure.

Changes from v3, v4: Fix patch formatting.

Changes from v5: Use 'bool' for on / off variables, don't change it87_find()
function arguments to minimize the changes.

Changes from v6: Add __maybe_unused to it87_resume_sio(), move a message
about failure to enter Super I/O on resume to this function, make it clear
what had actually failed and downgrade it to a warning.

 drivers/hwmon/it87.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 76 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/it87.c b/drivers/hwmon/it87.c
index 818f123ac475..a36d5947c1f6 100644
--- a/drivers/hwmon/it87.c
+++ b/drivers/hwmon/it87.c
@@ -497,12 +497,14 @@ static const struct it87_devices it87_devices[] = {
 #define has_vin3_5v(data)      ((data)->features & FEAT_VIN3_5V)
 
 struct it87_sio_data {
+       int sioaddr;
        enum chips type;
        /* Values read from Super-I/O config space */
        u8 revision;
        u8 vid_value;
        u8 beep_pin;
        u8 internal;    /* Internal sensors can be labeled */
+       bool need_in7_reroute;
        /* Features skipped based on config or DMI */
        u16 skip_in;
        u8 skip_vid;
@@ -517,6 +519,7 @@ struct it87_sio_data {
  */
 struct it87_data {
        const struct attribute_group *groups[7];
+       int sioaddr;
        enum chips type;
        u32 features;
        u8 peci_mask;
@@ -532,6 +535,7 @@ struct it87_data {
        u16 in_internal;        /* Bitfield, internal sensors (for labels) */
        u16 has_in;             /* Bitfield, voltage sensors enabled */
        u8 in[NUM_VIN][3];              /* [nr][0]=in, [1]=min, [2]=max */
+       bool need_in7_reroute;
        u8 has_fan;             /* Bitfield, fans enabled */
        u16 fan[NUM_FAN][2];    /* Register values, [nr][0]=fan, [1]=min */
        u8 has_temp;            /* Bitfield, temp sensors enabled */
@@ -2487,6 +2491,7 @@ static int __init it87_find(int sioaddr, unsigned short 
*address,
        }
 
        err = 0;
+       sio_data->sioaddr = sioaddr;
        sio_data->revision = superio_inb(sioaddr, DEVREV) & 0x0f;
        pr_info("Found IT%04x%s chip at 0x%x, revision %d\n", chip_type,
                it87_devices[sio_data->type].suffix,
@@ -2575,6 +2580,7 @@ static int __init it87_find(int sioaddr, unsigned short 
*address,
                                reg2c |= BIT(1);
                                superio_outb(sioaddr, IT87_SIO_PINX2_REG,
                                             reg2c);
+                               sio_data->need_in7_reroute = true;
                                pr_notice("Routing internal VCCH5V to in7.\n");
                        }
                        pr_notice("in7 routed to internal voltage divider, with 
external pin disabled.\n");
@@ -2777,6 +2783,7 @@ static int __init it87_find(int sioaddr, unsigned short 
*address,
                if ((sio_data->type == it8720 || uart6) && !(reg & BIT(1))) {
                        reg |= BIT(1);
                        superio_outb(sioaddr, IT87_SIO_PINX2_REG, reg);
+                       sio_data->need_in7_reroute = true;
                        pr_notice("Routing internal VCCH5V to in7\n");
                }
                if (reg & BIT(0))
@@ -3024,8 +3031,6 @@ static int it87_check_pwm(struct device *dev)
                                 "PWM configuration is too broken to be 
fixed\n");
                }
 
-               dev_info(dev,
-                        "Detected broken BIOS defaults, disabling PWM 
interface\n");
                return 0;
        } else if (fix_pwm_polarity) {
                dev_info(dev,
@@ -3058,6 +3063,7 @@ static int it87_probe(struct platform_device *pdev)
                return -ENOMEM;
 
        data->addr = res->start;
+       data->sioaddr = sio_data->sioaddr;
        data->type = sio_data->type;
        data->features = it87_devices[sio_data->type].features;
        data->peci_mask = it87_devices[sio_data->type].peci_mask;
@@ -3096,6 +3102,9 @@ static int it87_probe(struct platform_device *pdev)
 
        /* Check PWM configuration */
        enable_pwm_interface = it87_check_pwm(dev);
+       if (!enable_pwm_interface)
+               dev_info(dev,
+                        "Detected broken BIOS defaults, disabling PWM 
interface\n");
 
        /* Starting with IT8721F, we handle scaling of internal voltages */
        if (has_12mv_adc(data)) {
@@ -3123,6 +3132,7 @@ static int it87_probe(struct platform_device *pdev)
        }
 
        data->in_internal = sio_data->internal;
+       data->need_in7_reroute = sio_data->need_in7_reroute;
        data->has_in = 0x3ff & ~sio_data->skip_in;
 
        if (has_six_temp(data)) {
@@ -3178,9 +3188,73 @@ static int it87_probe(struct platform_device *pdev)
        return PTR_ERR_OR_ZERO(hwmon_dev);
 }
 
+static int __maybe_unused it87_resume_sio(struct platform_device *pdev)
+{
+       struct it87_data *data = dev_get_drvdata(&pdev->dev);
+       int err;
+       int reg2c;
+
+       if (!data->need_in7_reroute)
+               return 0;
+
+       err = superio_enter(data->sioaddr);
+       if (err) {
+               dev_warn(&pdev->dev,
+                        "Unable to enter Super I/O to reroute in7 (%d)",
+                        err);
+               return err;
+       }
+
+       superio_select(data->sioaddr, GPIO);
+
+       reg2c = superio_inb(data->sioaddr, IT87_SIO_PINX2_REG);
+       if (!(reg2c & BIT(1))) {
+               dev_dbg(&pdev->dev,
+                       "Routing internal VCCH5V to in7 again");
+
+               reg2c |= BIT(1);
+               superio_outb(data->sioaddr, IT87_SIO_PINX2_REG,
+                            reg2c);
+       }
+
+       superio_exit(data->sioaddr);
+
+       return 0;
+}
+
+static int __maybe_unused it87_resume(struct device *dev)
+{
+       struct platform_device *pdev = to_platform_device(dev);
+       struct it87_data *data = dev_get_drvdata(dev);
+
+       it87_resume_sio(pdev);
+
+       mutex_lock(&data->update_lock);
+
+       it87_check_pwm(dev);
+       it87_check_limit_regs(data);
+       it87_check_voltage_monitors_reset(data);
+       it87_check_tachometers_reset(pdev);
+       it87_check_tachometers_16bit_mode(pdev);
+
+       it87_start_monitoring(data);
+
+       /* force update */
+       data->valid = 0;
+
+       mutex_unlock(&data->update_lock);
+
+       it87_update_device(dev);
+
+       return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(it87_dev_pm_ops, NULL, it87_resume);
+
 static struct platform_driver it87_driver = {
        .driver = {
                .name   = DRVNAME,
+               .pm     = &it87_dev_pm_ops,
        },
        .probe  = it87_probe,
 };

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