The I2C-bus to the XPower AXP288 is shared between the Linux kernel and
the SoCs PUNIT. The PUNIT 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.

The default exec_mipi_pmic_seq_element implementation from
drivers/acpi/pmic/intel_pmic.c does a regmap_update_bits() call and
the involved registers are typically marked as volatile in the regmap,
so this leads to 2 I2C-bus accesses.

Add a XPower AXP288 specific implementation of exec_mipi_pmic_seq_element
which calls iosf_mbi_block_punit_i2c_access() calls before the
regmap_update_bits() call to avoid having to do the whole expensive
acquire PUNIT semaphore dance twice.

Signed-off-by: Hans de Goede <redacted>
---
 drivers/acpi/pmic/intel_pmic_xpower.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/acpi/pmic/intel_pmic_xpower.c b/drivers/acpi/pmic/intel_pmic_xpower.c
index 644a495a4f13..93c516ad361e 100644
--- a/drivers/acpi/pmic/intel_pmic_xpower.c
+++ b/drivers/acpi/pmic/intel_pmic_xpower.c

@@ -266,10 +266,34 @@ static int intel_xpower_pmic_get_raw_temp(struct regmap *regmap, int reg)
 	return ret;
 }
 
+static int intel_xpower_exec_mipi_pmic_seq_element(struct regmap *regmap,
+						   u16 i2c_address, u32 reg_address,
+						   u32 value, u32 mask)
+{
+	int ret;
+
+	if (i2c_address != 0x34) {
+		pr_err("%s: Unexpected i2c-addr: 0x%02x (reg-addr 0x%x value 0x%x mask 0x%x)\n",
+		       __func__, i2c_address, reg_address, value, mask);
+		return -ENXIO;
+	}
+
+	ret = iosf_mbi_block_punit_i2c_access();
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(regmap, reg_address, mask, value);
+
+	iosf_mbi_unblock_punit_i2c_access();
+
+	return ret;
+}
+
 static struct intel_pmic_opregion_data intel_xpower_pmic_opregion_data = {
 	.get_power = intel_xpower_pmic_get_power,
 	.update_power = intel_xpower_pmic_update_power,
 	.get_raw_temp = intel_xpower_pmic_get_raw_temp,
+	.exec_mipi_pmic_seq_element = intel_xpower_exec_mipi_pmic_seq_element,
 	.power_table = power_table,
 	.power_table_count = ARRAY_SIZE(power_table),
 	.thermal_table = thermal_table,

-- 
2.31.1