| Message ID | 1472283570-31471-1-git-send-email-zhuo-hao.lee@intel.com |
|---|---|
| State | Accepted |
| Headers | show |
On Sat, 2016-08-27 at 15:39 +0800, Zhuo-hao Lee wrote: > 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. Looks good to me. Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > > Signed-off-by: Zhuo-hao Lee <zhuo-hao.lee@intel.com> > --- > drivers/i2c/busses/i2c-designware-core.c | 16 ++++++++++------ > 1 file changed, 10 insertions(+), 6 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-designware-core.c > b/drivers/i2c/busses/i2c-designware-core.c > index c6922b8..fcd973d 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 */
On 08/28/2016 03:31 PM, Andy Shevchenko wrote: > On Sat, 2016-08-27 at 15:39 +0800, Zhuo-hao Lee wrote: >> 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. > > Looks good to me. > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com> -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Aug 27, 2016 at 03:39:30PM +0800, Zhuo-hao Lee wrote: > 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> Looks good. But is it a bugfix? Looks more like for-next material to me, but not sure...
>On Sat, Aug 27, 2016 at 03:39:30PM +0800, Zhuo-hao Lee wrote: >> 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> >Looks good. But is it a bugfix? Looks more like for-next material to me, but not sure... Yes, as least for me, this is a bug. This is an error handling in case Device Tree, built-in device properties and ACPI were not set the SDA hold time. We should use the firmware setting instead of chipset reset value. -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Aug 27, 2016 at 03:39:30PM +0800, Zhuo-hao Lee wrote: > 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> Applied to for-current, thanks!
diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c index c6922b8..fcd973d 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 */
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> --- drivers/i2c/busses/i2c-designware-core.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)