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Groups > linux.kernel > #1472956
| From | "Lee, Zhuo-hao" <zhuo-hao.lee@intel.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | RE: [PATCH v1] i2c: designware: save the preset value of DW_IC_SDA_HOLD |
| Date | 2016-08-31 02:30 +0200 |
| Message-ID | <sc1zH-3CS-3@gated-at.bofh.it> (permalink) |
| References | <saGxk-1I7-1@gated-at.bofh.it> <sbYs9-1JI-17@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
>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.
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[PATCH v1] i2c: designware: save the preset value of DW_IC_SDA_HOLD Zhuo-hao Lee <zhuo-hao.lee@intel.com> - 2016-08-27 09:50 +0200
Re: [PATCH v1] i2c: designware: save the preset value of DW_IC_SDA_HOLD Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-08-28 14:40 +0200
Re: [PATCH v1] i2c: designware: save the preset value of DW_IC_SDA_HOLD Jarkko Nikula <jarkko.nikula@linux.intel.com> - 2016-08-29 08:20 +0200
Re: [PATCH v1] i2c: designware: save the preset value of DW_IC_SDA_HOLD Wolfram Sang <wsa@the-dreams.de> - 2016-08-30 23:10 +0200
RE: [PATCH v1] i2c: designware: save the preset value of DW_IC_SDA_HOLD "Lee, Zhuo-hao" <zhuo-hao.lee@intel.com> - 2016-08-31 02:30 +0200
Re: [PATCH v1] i2c: designware: save the preset value of DW_IC_SDA_HOLD Wolfram Sang <wsa@the-dreams.de> - 2016-09-08 22:20 +0200
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