[PATCH v2] extcon: extcon-axp288: use P-Unit semaphore lock for register accesses

[Fabio Aiuto <fabioaiuto83@gmail.com>]

use low level P-Unit semaphore lock for axp288 register
accesses directly and for more than one access a time,
to reduce the number of times this semaphore is locked
and released which is an expensive operation.

i2c-bus to the XPower is shared between the kernel and the
SoCs P-Unit. The P-Unit has a semaphore wich the kernel must
lock for axp288 register accesses. When the P-Unit semaphore
is locked CPU and GPU power states cannot change or the system
will freeze.

The P-Unit semaphore lock is already managed inside the regmap
access logic, but for each access the semaphore is locked and
released. So use directly iosf_mbi_(un)block_punit_i2c_access(),
we are safe in doing so because nested calls to the same
semaphore are turned to nops.

Suggested-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Fabio Aiuto <fabioaiuto83@gmail.com>
---
Changes in v2:
	- shortened patch title within 75 char
	- added return value check in function
	  iosf_mbi_lock_punit_i2c_access() calls

 drivers/extcon/Kconfig         |  2 +-
 drivers/extcon/extcon-axp288.c | 31 +++++++++++++++++++++++++++++--
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
index c69d40ae5619..aab87c9b35c8 100644
--- a/drivers/extcon/Kconfig
+++ b/drivers/extcon/Kconfig
@@ -23,7 +23,7 @@ config EXTCON_ADC_JACK
 
 config EXTCON_AXP288
 	tristate "X-Power AXP288 EXTCON support"
-	depends on MFD_AXP20X && USB_SUPPORT && X86 && ACPI
+	depends on MFD_AXP20X && USB_SUPPORT && X86 && ACPI && IOSF_MBI
 	select USB_ROLE_SWITCH
 	help
 	  Say Y here to enable support for USB peripheral detection
diff --git a/drivers/extcon/extcon-axp288.c b/drivers/extcon/extcon-axp288.c
index fdb31954cf2b..7c6d5857ff25 100644
--- a/drivers/extcon/extcon-axp288.c
+++ b/drivers/extcon/extcon-axp288.c
@@ -24,6 +24,7 @@
 
 #include <asm/cpu_device_id.h>
 #include <asm/intel-family.h>
+#include <asm/iosf_mbi.h>
 
 /* Power source status register */
 #define PS_STAT_VBUS_TRIGGER		BIT(0)
@@ -215,6 +216,10 @@ static int axp288_handle_chrg_det_event(struct axp288_extcon_info *info)
 	unsigned int cable = info->previous_cable;
 	bool vbus_attach = false;
 
+	ret = iosf_mbi_block_punit_i2c_access();
+	if (ret < 0)
+		return ret;
+
 	vbus_attach = axp288_get_vbus_attach(info);
 	if (!vbus_attach)
 		goto no_vbus;
@@ -253,6 +258,8 @@ static int axp288_handle_chrg_det_event(struct axp288_extcon_info *info)
 	}
 
 no_vbus:
+	iosf_mbi_unblock_punit_i2c_access();
+
 	extcon_set_state_sync(info->edev, info->previous_cable, false);
 	if (info->previous_cable == EXTCON_CHG_USB_SDP)
 		extcon_set_state_sync(info->edev, EXTCON_USB, false);
@@ -275,6 +282,8 @@ static int axp288_handle_chrg_det_event(struct axp288_extcon_info *info)
 	return 0;
 
 dev_det_ret:
+	iosf_mbi_unblock_punit_i2c_access();
+
 	if (ret < 0)
 		dev_err(info->dev, "failed to detect BC Mod\n");
 
@@ -305,13 +314,23 @@ static irqreturn_t axp288_extcon_isr(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
-static void axp288_extcon_enable(struct axp288_extcon_info *info)
+static int axp288_extcon_enable(struct axp288_extcon_info *info)
 {
+	int ret = 0;
+
+	ret = iosf_mbi_block_punit_i2c_access();
+	if (ret < 0)
+		return ret;
+
 	regmap_update_bits(info->regmap, AXP288_BC_GLOBAL_REG,
 						BC_GLOBAL_RUN, 0);
 	/* Enable the charger detection logic */
 	regmap_update_bits(info->regmap, AXP288_BC_GLOBAL_REG,
 					BC_GLOBAL_RUN, BC_GLOBAL_RUN);
+
+	iosf_mbi_unblock_punit_i2c_access();
+
+	return ret;
 }
 
 static void axp288_put_role_sw(void *data)
@@ -384,10 +403,16 @@ static int axp288_extcon_probe(struct platform_device *pdev)
 		}
 	}
 
+	ret = iosf_mbi_block_punit_i2c_access();
+	if (ret < 0)
+		return ret;
+
 	info->vbus_attach = axp288_get_vbus_attach(info);
 
 	axp288_extcon_log_rsi(info);
 
+	iosf_mbi_unblock_punit_i2c_access();
+
 	/* Initialize extcon device */
 	info->edev = devm_extcon_dev_allocate(&pdev->dev,
 					      axp288_extcon_cables);
@@ -441,7 +466,9 @@ static int axp288_extcon_probe(struct platform_device *pdev)
 	}
 
 	/* Start charger cable type detection */
-	axp288_extcon_enable(info);
+	ret = axp288_extcon_enable(info);
+	if (ret < 0)
+		return ret;
 
 	device_init_wakeup(dev, true);
 	platform_set_drvdata(pdev, info);
-- 
2.20.1