ACPI / PMIC: XPower: optimize MIPI PMIQ sequence 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.

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 P-Unit semaphore dance twice.

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 5750c5e..cbe08e6 100644 (file)
--- a/drivers/acpi/pmic/intel_pmic_xpower.c
+++ b/drivers/acpi/pmic/intel_pmic_xpower.c
@@ -270,10 +270,34 @@ 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,