diff options
| author | Geert Uytterhoeven <geert+renesas@glider.be> | 2024-11-22 15:14:35 +0100 |
|---|---|---|
| committer | Andi Shyti <andi.shyti@kernel.org> | 2024-12-12 12:54:02 +0100 |
| commit | de6b43798d9043a7c749a0428dbb02d5fff156e5 (patch) | |
| tree | 2d7851a97d6965b5998aec51f3824e21987b7e33 | |
| parent | 5751eee5c620c7e47a277ca929c4010caf24654c (diff) | |
i2c: riic: Always round-up when calculating bus period
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@bp.renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: <stable@vger.kernel.org> # v4.15+
Link: https://lore.kernel.org/r/c59aea77998dfea1b4456c4b33b55ab216fcbf5e.1732284746.git.geert+renesas@glider.be
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
| -rw-r--r-- | drivers/i2c/busses/i2c-riic.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/i2c/busses/i2c-riic.c b/drivers/i2c/busses/i2c-riic.c index c218f73c3650..9264adc97ca9 100644 --- a/drivers/i2c/busses/i2c-riic.c +++ b/drivers/i2c/busses/i2c-riic.c @@ -352,7 +352,7 @@ static int riic_init_hw(struct riic_dev *riic) if (brl <= (0x1F + 3)) break; - total_ticks /= 2; + total_ticks = DIV_ROUND_UP(total_ticks, 2); rate /= 2; } |