ACPI / PMIC: XPower: optimize I2C-bus accesses

The I2C-bus to the XPower AXP288 is shared between the Linux kernel and
the SoCs P-Unit. The P-Unit has a semaphore which the kernel must "lock"
before it may use the bus and while the kernel holds the semaphore the CPU
and GPU power-states must not be changed otherwise the system will freeze.

This is a complex process, which is quite expensive. This is all done by
iosf_mbi_block_punit_i2c_access(). To ensure that no unguarded I2C-bus
accesses happen, iosf_mbi_block_punit_i2c_access() gets called by the
I2C-bus-driver for every I2C transfer. Because this is so expensive it
is allowed to call iosf_mbi_block_punit_i2c_access() in a nested
fashion, so that higher-level code which does multiple I2C-transfers can
call it once for a group of transfers, turning the calls done by the
I2C-bus-driver into no-ops.

Add iosf_mbi_block_punit_i2c_access() calls around groups of register
accesses, so that the P-Unit semaphore only needs to be taken once
for each group of register accesses.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/pmic/intel_pmic_xpower.c b/drivers/acpi/pmic/intel_pmic_xpower.c
index a091d5a..5750c5e 100644 (file)
--- a/drivers/acpi/pmic/intel_pmic_xpower.c
+++ b/drivers/acpi/pmic/intel_pmic_xpower.c
@@ -178,15 +178,17 @@ static int intel_xpower_pmic_update_power(struct regmap *regmap, int reg,
 {
        int data, ret;
 
-       /* GPIO1 LDO regulator needs special handling */
-       if (reg == XPOWER_GPI1_CTRL)
-               return regmap_update_bits(regmap, reg, GPI1_LDO_MASK,
-                                         on ? GPI1_LDO_ON : GPI1_LDO_OFF);
-
        ret = iosf_mbi_block_punit_i2c_access();
        if (ret)
                return ret;
 
+       /* GPIO1 LDO regulator needs special handling */
+       if (reg == XPOWER_GPI1_CTRL) {
+               ret = regmap_update_bits(regmap, reg, GPI1_LDO_MASK,
+                                        on ? GPI1_LDO_ON : GPI1_LDO_OFF);
+               goto out;
+       }
+
        if (regmap_read(regmap, reg, &data)) {
                ret = -EIO;
                goto out;
@@ -234,6 +236,11 @@ static int intel_xpower_pmic_get_raw_temp(struct regmap *regmap, int reg)
                return ret;
 
        if (adc_ts_pin_ctrl & AXP288_ADC_TS_CURRENT_ON_OFF_MASK) {
+               /*
+                * AXP288_ADC_TS_PIN_CTRL reads are cached by the regmap, so
+                * this does to a single I2C-transfer, and thus there is no
+                * need to explicitly call iosf_mbi_block_punit_i2c_access().
+                */
                ret = regmap_update_bits(regmap, AXP288_ADC_TS_PIN_CTRL,
                                         AXP288_ADC_TS_CURRENT_ON_OFF_MASK,
                                         AXP288_ADC_TS_CURRENT_ON_ONDEMAND);
@@ -244,6 +251,10 @@ static int intel_xpower_pmic_get_raw_temp(struct regmap *regmap, int reg)
                usleep_range(6000, 10000);
        }
 
+       ret = iosf_mbi_block_punit_i2c_access();
+       if (ret)
+               return ret;
+
        ret = regmap_bulk_read(regmap, AXP288_GP_ADC_H, buf, 2);
        if (ret == 0)
                ret = (buf[0] << 4) + ((buf[1] >> 4) & 0x0f);
@@ -254,6 +265,8 @@ static int intel_xpower_pmic_get_raw_temp(struct regmap *regmap, int reg)
                                   AXP288_ADC_TS_CURRENT_ON);
        }
 
+       iosf_mbi_unblock_punit_i2c_access();
+
        return ret;
 }