The I2C spec UM10204 Rev. 6 specifies the following timings.
Standard Fast Mode Fast Mode Plus
SCL low 4.7us 1.3us 0.5us
SCL high 4.0us 0.6us 0.26us
This results in a 33%/66% duty cycle as opposed to the 50%/50% duty cycle
used for Standard-mode.
Add High Time Divider settings to correct duty cycle for FM(400kHz) and
FM+(1MHz).
Signed-off-by: Austin Christ <austinwc@xxxxxxxxxxxxxx>
---
drivers/i2c/busses/i2c-qup.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
index ce5f215..f87f29f 100644
--- a/drivers/i2c/busses/i2c-qup.c
+++ b/drivers/i2c/busses/i2c-qup.c
@@ -1855,9 +1855,15 @@ static int qup_i2c_probe(struct platform_device *pdev)
size = QUP_INPUT_FIFO_SIZE(io_mode);
qup->in_fifo_sz = qup->in_blk_sz * (2 << size);
- fs_div = ((src_clk_freq / clk_freq) / 2) - 3;
hs_div = 3;
- qup->clk_ctl = (hs_div << 8) | (fs_div & 0xff);
+ if (clk_freq <= I2C_STANDARD_FREQ) {
+ fs_div = ((src_clk_freq / clk_freq) / 2) - 3;
+ qup->clk_ctl = (hs_div << 8) | (fs_div & 0xff);
+ } else {
+ /* 33%/66% duty cycle */
+ fs_div = ((src_clk_freq / clk_freq) - 6) * 2 / 3;
+ qup->clk_ctl = ((fs_div / 2) << 16) | (hs_div << 8) | (fs_div & 0xff);
+ }
/*
* Time it takes for a byte to be clocked out on the bus.
--
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