Commit 7ce98a55 authored by Wolfram Sang's avatar Wolfram Sang Committed by Wolfram Sang
Browse files

i2c: rcar: explain the lockless design 



To make sure people can understand the lockless design of this driver
without the need to dive into git history, add a comment giving an
overview of the situation.

Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: default avatarSimon Horman <horms+renesas@verge.net.au>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent a35ba2f7

drivers/i2c/busses/i2c-rcar.c

+9 −0
Original line number Diff line number Diff line
@@ -611,6 +611,15 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv) 
	return true;

}



/*

 * This driver has a lock-free design because there are IP cores (at least

 * R-Car Gen2) which have an inherent race condition in their hardware design.

 * There, we need to clear RCAR_BUS_MASK_DATA bits as soon as possible after

 * the interrupt was generated, otherwise an unwanted repeated message gets

 * generated. It turned out that taking a spinlock at the beginning of the ISR

 * was already causing repeated messages. Thus, this driver was converted to

 * the now lockless behaviour. Please keep this in mind when hacking the driver.

 */

static irqreturn_t rcar_i2c_irq(int irq, void *ptr)

{

	struct rcar_i2c_priv *priv = ptr;

CRA Git | Maintained and supported by SUSTech CRA and CCSE