[PATCH v2] i2c: rk3x: fix potential spinlock recursion on poll

[Jensen Huang]

Possible deadlock scenario (on reboot):
rk3x_i2c_xfer_common(polling)
    -> rk3x_i2c_wait_xfer_poll()
        -> rk3x_i2c_irq(0, i2c);
            --> spin_lock(&i2c->lock);
            ...
        <rk3x i2c interrupt>
        -> rk3x_i2c_irq(0, i2c);
            --> spin_lock(&i2c->lock); (deadlock here)

Store the IRQ number and disable/enable it around the polling transfer.
This patch has been tested on NanoPC-T4.

Signed-off-by: Jensen Huang <jensenhuang at friendlyarm.com>
Reviewed-by: Heiko Stuebner <heiko at sntech.de>
Reviewed-by: Andi Shyti <andi.shyti at kernel.org>
---
Changes in v2:
 - Add description for member 'irq' to fix build warning

 drivers/i2c/busses/i2c-rk3x.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
index a044ca0c35a1..4362db7c5789 100644
--- a/drivers/i2c/busses/i2c-rk3x.c
+++ b/drivers/i2c/busses/i2c-rk3x.c
@@ -178,6 +178,7 @@ struct rk3x_i2c_soc_data {
  * @clk: function clk for rk3399 or function & Bus clks for others
  * @pclk: Bus clk for rk3399
  * @clk_rate_nb: i2c clk rate change notify
+ * @irq: irq number
  * @t: I2C known timing information
  * @lock: spinlock for the i2c bus
  * @wait: the waitqueue to wait for i2c transfer
@@ -200,6 +201,7 @@ struct rk3x_i2c {
 	struct clk *clk;
 	struct clk *pclk;
 	struct notifier_block clk_rate_nb;
+	int irq;
 
 	/* Settings */
 	struct i2c_timings t;
@@ -1087,13 +1089,18 @@ static int rk3x_i2c_xfer_common(struct i2c_adapter *adap,
 
 		spin_unlock_irqrestore(&i2c->lock, flags);
 
-		rk3x_i2c_start(i2c);
-
 		if (!polling) {
+			rk3x_i2c_start(i2c);
+
 			timeout = wait_event_timeout(i2c->wait, !i2c->busy,
 						     msecs_to_jiffies(WAIT_TIMEOUT));
 		} else {
+			disable_irq(i2c->irq);
+			rk3x_i2c_start(i2c);
+
 			timeout = rk3x_i2c_wait_xfer_poll(i2c);
+
+			enable_irq(i2c->irq);
 		}
 
 		spin_lock_irqsave(&i2c->lock, flags);
@@ -1310,6 +1317,8 @@ static int rk3x_i2c_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	i2c->irq = irq;
+
 	platform_set_drvdata(pdev, i2c);
 
 	if (i2c->soc_data->calc_timings == rk3x_i2c_v0_calc_timings) {
-- 
2.42.0