From 973652db6f1406e556613b7bb252f1a005005f04 Mon Sep 17 00:00:00 2001 From: Jarkko Nikula Date: Thu, 10 Nov 2016 13:37:20 +0200 Subject: [PATCH] i2c: designware: Allow reduce bus speed by "clock-frequency" property Allow more flexibility to bus speed selection. Now if there are I2C slave connections defined in ACPI the speed of slowest device on the bus will define the bus speed. However if also "clock-frequency" device property is defined we should use the slowest of these two. This is targeted to maker boards where developer may want to connect slower I2C slave devices to the bus than defined in existing ACPI I2C slave connections. Signed-off-by: Jarkko Nikula Reviewed-by: Mika Westerberg Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-designware-platdrv.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c index 886fb622ca38..7429dfa39440 100644 --- a/drivers/i2c/busses/i2c-designware-platdrv.c +++ b/drivers/i2c/busses/i2c-designware-platdrv.c @@ -176,9 +176,6 @@ static int dw_i2c_plat_probe(struct platform_device *pdev) dev->irq = irq; platform_set_drvdata(pdev, dev); - /* fast mode by default because of legacy reasons */ - dev->clk_freq = 400000; - if (pdata) { dev->clk_freq = pdata->i2c_scl_freq; } else { @@ -193,8 +190,16 @@ static int dw_i2c_plat_probe(struct platform_device *pdev) } acpi_speed = i2c_acpi_find_bus_speed(&pdev->dev); - if (acpi_speed) - dev->clk_freq = acpi_speed; + /* + * Find bus speed from the "clock-frequency" device property, ACPI + * or by using fast mode if neither is set. + */ + if (acpi_speed && dev->clk_freq) + dev->clk_freq = min(dev->clk_freq, acpi_speed); + else if (acpi_speed || dev->clk_freq) + dev->clk_freq = max(dev->clk_freq, acpi_speed); + else + dev->clk_freq = 400000; if (has_acpi_companion(&pdev->dev)) dw_i2c_acpi_configure(pdev); -- GitLab