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authorZhuo-hao Lee <zhuo-hao.lee@intel.com>2016-08-27 15:39:30 +0800
committerWolfram Sang <wsa@the-dreams.de>2016-09-08 22:14:36 +0200
commit664d58bf4d3406dc4404e29bcb8c89fd22589d57 (patch)
tree8096bcb43ea1dbc7d623313bc14413591168d6da /drivers/i2c
parent30851a7c2155d0b321485e66386ea99191d8b3f5 (diff)
i2c: designware: save the preset value of DW_IC_SDA_HOLD
There are several ways to set the SDA hold time for i2c controller, including: Device Tree, built-in device properties and ACPI. However, if the SDA hold time is not specified by above method, we should read the value, where it is preset by firmware, and save it to sda_hold_time. This is needed because when i2c controller enters runtime suspend, the DW_IC_SDA_HOLD value will be reset to chipset default value. And during runtime resume, i2c_dw_init will be called to reconfigure i2c controller. If sda_hold_time is zero, the chipset default hold time will be used, that will be too short for some platforms. Therefore, to have a better tolerance, the DW_IC_SDA_HOLD value should be kept by sda_hold_time. Signed-off-by: Zhuo-hao Lee <zhuo-hao.lee@intel.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/busses/i2c-designware-core.c16
1 files changed, 10 insertions, 6 deletions
diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index c6922b806fb7..fcd973d5131e 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -367,13 +367,17 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
dev_dbg(dev->dev, "Fast-mode HCNT:LCNT = %d:%d\n", hcnt, lcnt);
/* Configure SDA Hold Time if required */
- if (dev->sda_hold_time) {
- reg = dw_readl(dev, DW_IC_COMP_VERSION);
- if (reg >= DW_IC_SDA_HOLD_MIN_VERS)
+ reg = dw_readl(dev, DW_IC_COMP_VERSION);
+ if (reg >= DW_IC_SDA_HOLD_MIN_VERS) {
+ if (dev->sda_hold_time) {
dw_writel(dev, dev->sda_hold_time, DW_IC_SDA_HOLD);
- else
- dev_warn(dev->dev,
- "Hardware too old to adjust SDA hold time.");
+ } else {
+ /* Keep previous hold time setting if no one set it */
+ dev->sda_hold_time = dw_readl(dev, DW_IC_SDA_HOLD);
+ }
+ } else {
+ dev_warn(dev->dev,
+ "Hardware too old to adjust SDA hold time.\n");
}
/* Configure Tx/Rx FIFO threshold levels */