This is a note to let you know that I've just added the patch titled
i2c: rcar: faster irq code to minimize HW race condition
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
i2c-rcar-faster-irq-code-to-minimize-hw-race-conditi.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9dc6645eae4020bbaeb7b18b34672d72fde77482
Author: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Date: Wed Dec 23 18:21:51 2020 +0100
i2c: rcar: faster irq code to minimize HW race condition
[ Upstream commit c7b514ec979e23a08c411f3d8ed39c7922751422 ]
To avoid the HW race condition on R-Car Gen2 and earlier, we need to
write to ICMCR as soon as possible in the interrupt handler. We can
improve this by writing a static value instead of masking out bits.
Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 217def2d7cb4..824586d7ee56 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -91,7 +91,6 @@
#define RCAR_BUS_PHASE_START (MDBS | MIE | ESG)
#define RCAR_BUS_PHASE_DATA (MDBS | MIE)
-#define RCAR_BUS_MASK_DATA (~(ESG | FSB) & 0xFF)
#define RCAR_BUS_PHASE_STOP (MDBS | MIE | FSB)
#define RCAR_IRQ_SEND (MNR | MAL | MST | MAT | MDE)
@@ -621,7 +620,7 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
/*
* 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
+ * There, we need to switch to RCAR_BUS_PHASE_DATA 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
@@ -630,13 +629,11 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
{
struct rcar_i2c_priv *priv = ptr;
- u32 msr, val;
+ u32 msr;
/* Clear START or STOP immediately, except for REPSTART after read */
- if (likely(!(priv->flags & ID_P_REP_AFTER_RD))) {
- val = rcar_i2c_read(priv, ICMCR);
- rcar_i2c_write(priv, ICMCR, val & RCAR_BUS_MASK_DATA);
- }
+ if (likely(!(priv->flags & ID_P_REP_AFTER_RD)))
+ rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);
msr = rcar_i2c_read(priv, ICMSR);
