[PATCH v4 3/3] i2c: s3c24xx: add support for atomic transfers

[Marek Szyprowski <m.szyprowski@samsung.com>]

Add support for atomic transfers using polling mode with interrupts
intentionally disabled to get rid of the following warning introduced by
commit 63b96983a5dd ("i2c: core: introduce callbacks for atomic
transfers") during system reboot and power-off:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 1518 at drivers/i2c/i2c-core.h:40 i2c_transfer+0xe8/0xf4
No atomic I2C transfer handler for 'i2c-0'
Modules linked in:
CPU: 0 PID: 1518 Comm: reboot Not tainted 6.6.0-next-20231031 #7453
Hardware name: Samsung Exynos (Flattened Device Tree)
 unwind_backtrace from show_stack+0x10/0x14
 show_stack from dump_stack_lvl+0x40/0x4c
 dump_stack_lvl from __warn+0x7c/0x124
 __warn from warn_slowpath_fmt+0x110/0x178
 warn_slowpath_fmt from i2c_transfer+0xe8/0xf4
 i2c_transfer from regmap_i2c_read+0x58/0x88
 regmap_i2c_read from _regmap_raw_read+0xfc/0x260
 _regmap_raw_read from _regmap_bus_read+0x44/0x70
 _regmap_bus_read from _regmap_read+0x60/0x14c
 _regmap_read from regmap_read+0x3c/0x60
 regmap_read from regulator_get_voltage_sel_regmap+0x2c/0x74
 regulator_get_voltage_sel_regmap from regulator_get_voltage_rdev+0x64/0x15c
 regulator_get_voltage_rdev from _regulator_do_set_voltage+0x2c/0x5a8
 _regulator_do_set_voltage from regulator_set_voltage_rdev+0x90/0x248
 regulator_set_voltage_rdev from regulator_do_balance_voltage+0x350/0x4d0
 regulator_do_balance_voltage from regulator_set_voltage_unlocked+0xd4/0x118
 regulator_set_voltage_unlocked from regulator_set_voltage+0x40/0x74
 regulator_set_voltage from _opp_config_regulator_single+0x44/0x110
 _opp_config_regulator_single from _set_opp+0x118/0x500
 _set_opp from dev_pm_opp_set_rate+0x108/0x20c
 dev_pm_opp_set_rate from __cpufreq_driver_target+0x568/0x6cc
 __cpufreq_driver_target from cpufreq_generic_suspend+0x28/0x50
 cpufreq_generic_suspend from cpufreq_suspend+0xbc/0x124
 cpufreq_suspend from device_shutdown+0x18/0x230
 device_shutdown from kernel_restart+0x38/0x90
 kernel_restart from __do_sys_reboot+0x12c/0x1f8
 __do_sys_reboot from ret_fast_syscall+0x0/0x54
Exception stack(0xf0fedfa8 to 0xf0fedff0)
...
---[ end trace 0000000000000000 ]---

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Chanho Park <chanho61.park@samsung.com>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
---
 drivers/i2c/busses/i2c-s3c2410.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index c0fe96a4f2c4..275f7c42165c 100644
--- a/drivers/i2c/busses/i2c-s3c2410.c
+++ b/drivers/i2c/busses/i2c-s3c2410.c
@@ -76,6 +76,7 @@
 #define QUIRK_HDMIPHY		(1 << 1)
 #define QUIRK_NO_GPIO		(1 << 2)
 #define QUIRK_POLL		(1 << 3)
+#define QUIRK_ATOMIC		(1 << 4)
 
 /* Max time to wait for bus to become idle after a xfer (in us) */
 #define S3C2410_IDLE_TIMEOUT	5000
@@ -174,7 +175,7 @@ static inline void s3c24xx_i2c_master_complete(struct s3c24xx_i2c *i2c, int ret)
 	if (ret)
 		i2c->msg_idx = ret;
 
-	if (!(i2c->quirks & QUIRK_POLL))
+	if (!(i2c->quirks & (QUIRK_POLL | QUIRK_ATOMIC)))
 		wake_up(&i2c->wait);
 }
 
@@ -703,7 +704,7 @@ static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c,
 	s3c24xx_i2c_enable_irq(i2c);
 	s3c24xx_i2c_message_start(i2c, msgs);
 
-	if (i2c->quirks & QUIRK_POLL) {
+	if (i2c->quirks & (QUIRK_POLL | QUIRK_ATOMIC)) {
 		while ((i2c->msg_num != 0) && is_ack(i2c)) {
 			unsigned long stat = readl(i2c->regs + S3C2410_IICSTAT);
 
@@ -775,6 +776,21 @@ static int s3c24xx_i2c_xfer(struct i2c_adapter *adap,
 	return -EREMOTEIO;
 }
 
+static int s3c24xx_i2c_xfer_atomic(struct i2c_adapter *adap,
+				   struct i2c_msg *msgs, int num)
+{
+	struct s3c24xx_i2c *i2c = (struct s3c24xx_i2c *)adap->algo_data;
+	int ret;
+
+	disable_irq(i2c->irq);
+	i2c->quirks |= QUIRK_ATOMIC;
+	ret = s3c24xx_i2c_xfer(adap, msgs, num);
+	i2c->quirks &= ~QUIRK_ATOMIC;
+	enable_irq(i2c->irq);
+
+	return ret;
+}
+
 /* declare our i2c functionality */
 static u32 s3c24xx_i2c_func(struct i2c_adapter *adap)
 {
@@ -785,6 +801,7 @@ static u32 s3c24xx_i2c_func(struct i2c_adapter *adap)
 /* i2c bus registration info */
 static const struct i2c_algorithm s3c24xx_i2c_algorithm = {
 	.master_xfer		= s3c24xx_i2c_xfer,
+	.master_xfer_atomic     = s3c24xx_i2c_xfer_atomic,
 	.functionality		= s3c24xx_i2c_func,
 };
 
-- 
2.34.1