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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Thu,  9 Sep 2021 17:18:20 +0200
From:   Fabio Aiuto <fabioaiuto83@...il.com>
To:     Chanwoo Choi <cw00.choi@...sung.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-kernel@...r.kernel.org, Fabio Aiuto <fabioaiuto83@...il.com>
Subject: [PATCH] extcon: extcon-axp288: use low level P-Unit semaphore lock for axp288 register accesses

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@...hat.com>
Signed-off-by: Fabio Aiuto <fabioaiuto83@...il.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