6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
commit de6b43798d9043a7c749a0428dbb02d5fff156e5 upstream.
Currently, the RIIC driver may run the I2C bus faster than requested,
which may cause subtle failures. E.g. Biju reported a measured bus
speed of 450 kHz instead of the expected maximum of 400 kHz on RZ/G2L.
The initial calculation of the bus period uses DIV_ROUND_UP(), to make
sure the actual bus speed never becomes faster than the requested bus
speed. However, the subsequent division-by-two steps do not use
round-up, which may lead to a too-small period, hence a too-fast and
possible out-of-spec bus speed. E.g. on RZ/Five, requesting a bus speed
of 100 resp. 400 kHz will yield too-fast target bus speeds of 100806
resp. 403226 Hz instead of 97656 resp. 390625 Hz.
Fix this by using DIV_ROUND_UP() in the subsequent divisions, too.
Tested on RZ/A1H, RZ/A2M, and RZ/Five.
Fixes: d982d66514192cdb ("i2c: riic: remove clock and frequency restrictions")
Reported-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.15+
Link: https://lore.kernel.org/r/c59aea77998dfea1b4456c4b33b55ab216fcbf5e.1732284746.git.geert+renesas@xxxxxxxxx
Signed-off-by: Andi Shyti <andi.shyti@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/i2c/busses/i2c-riic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/i2c/busses/i2c-riic.c
+++ b/drivers/i2c/busses/i2c-riic.c
@@ -324,7 +324,7 @@ static int riic_init_hw(struct riic_dev
if (brl <= (0x1F + 3))
break;
- total_ticks /= 2;
+ total_ticks = DIV_ROUND_UP(total_ticks, 2);
rate /= 2;
}
