[PATCH 3/4] i2c: qup: Correct duty cycle for FM and FM+

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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 cb14687..2a88611 100644
--- a/drivers/i2c/busses/i2c-qup.c
+++ b/drivers/i2c/busses/i2c-qup.c
@@ -1858,9 +1858,15 @@ 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.
-- 
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

--
To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [Linux for Sparc]     [IETF Annouce]     [Security]     [Bugtraq]     [Linux MIPS]     [ECOS]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux