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

Fabio Aiuto
2021-09-09T15:18:44Z

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>
Signed-off-by: Fabio Aiuto <fabioaiuto83@gmail.com>
---
drivers/extcon/extcon-axp288.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/drivers/extcon/extcon-axp288.c b/drivers/extcon/extcon-axp288.c
index fdb31954cf2b..460402b14ef2 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 +216,8 @@ static int axp288_handle_chrg_det_event(struct axp288_extcon_info *info)
unsigned int cable = info->previous_cable;
bool vbus_attach = false;

+ iosf_mbi_block_punit_i2c_access();
+
vbus_attach = axp288_get_vbus_attach(info);
if (!vbus_attach)
goto no_vbus;
@@ -253,6 +256,8 @@ 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 +280,8 @@ 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");

@@ -307,11 +314,14 @@ static irqreturn_t axp288_extcon_isr(int irq, void *data)

static void axp288_extcon_enable(struct axp288_extcon_info *info)
{
+ iosf_mbi_block_punit_i2c_access();
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();
}

static void axp288_put_role_sw(void *data)
@@ -384,10 +394,14 @@ static int axp288_extcon_probe(struct platform_device *pdev)
}
}

+ iosf_mbi_block_punit_i2c_access();
+
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);
--
2.20.1