Re: [PATCH v2 14/16] mfd: intel-lpss: Pass SDA hold time to I2C host controller driver

On Mon, Feb 8, 2016 at 12:29 PM, Mika Westerberg
[off-list ref] wrote:

On Mon, Feb 08, 2016 at 11:09:43AM +0100, Wolfram Sang wrote:

quoted

On Mon, Nov 30, 2015 at 05:11:42PM +0200, Andy Shevchenko wrote:

quoted

There has been a request to get this into stable:

https://bugzilla.kernel.org/show_bug.cgi?id=108581

Since we probably don't want to backport the whole device_property
series, is there a simpler fix to backport for stable?

Basically all it needs is to have:

        dev->sda_hold_time = 28

in dw_i2c_acpi_configure(). However, we cannot just unconditionally set
it as it will break existing non-SKL systems so there should be some way
to check if this is SKL or not. Perhaps we could look for DMI entries of
the affected machines?

BTW, this is not a regression in a sense as SKL I2C never worked before
this series.

I could add that "backporting" something which is drastically
different to the original mainstream may probably prevent a smooth
backporting the fixes come later if any. Thus, I would try to port as
much closer as we can to the existing upstream code.

-- 
With Best Regards,
Andy Shevchenko