From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: "Lawrence,Wang" <lawrence.wang@nokia-sbell.com>
Cc: jarkko.nikula@linux.intel.com, mika.westerberg@linux.intel.com,
linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
Wang@wrlinb193.emea.nsn-net.net
Subject: Re: [PATCH] i2c: designware: Get HCNT/LCNT values from dts
Date: Mon, 15 Nov 2021 12:28:22 +0200 [thread overview]
Message-ID: <YZI2RnFgO0Y75KlF@smile.fi.intel.com> (raw)
In-Reply-To: <YZI0LuDK63+Wb7wi@smile.fi.intel.com>
On Mon, Nov 15, 2021 at 12:19:26PM +0200, Andy Shevchenko wrote:
> On Mon, Nov 15, 2021 at 10:35:55AM +0100, Lawrence,Wang wrote:
> > From: "Wang, Lawrence" <lawrence.wang@nokia-sbell.com>
> >
> > Current code support config the HCNT/LCNT only via ACPI method. for those
> > platform that not support ACPI, will get the HCNT/LCNT value based on input
> > clock. But it is not always accuracy. for example in some platform will get
> > lower speed(320khz) in fast mode, and get faster speed(105khz/even more) in
> > standard mode.
> >
> > This patch makes it possible for the non-ACPI platform to pass more optimal
> > HCNT/LCNT values to the core driver via dts if they are known beforehand.
> > If these are not set we use the calculated values.
>
> Besides the fact it misses DT schema update, why this is needed at all?
> What's wrong with the existing DT timings?
Just for your convenience an excerpt from
Documentation/devicetree/bindings/i2c/i2c.txt
- i2c-scl-falling-time-ns
Number of nanoseconds the SCL signal takes to fall; t(f) in the I2C
specification.
- i2c-scl-internal-delay-ns
Number of nanoseconds the IP core additionally needs to setup SCL.
- i2c-scl-rising-time-ns
Number of nanoseconds the SCL signal takes to rise; t(r) in the I2C
specification.
- i2c-sda-falling-time-ns
Number of nanoseconds the SDA signal takes to fall; t(f) in the I2C
specification.
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2021-11-15 10:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-15 9:35 [PATCH] i2c: designware: Get HCNT/LCNT values from dts Lawrence,Wang
2021-11-15 10:19 ` Andy Shevchenko
2021-11-15 10:28 ` Andy Shevchenko [this message]
2021-11-15 10:41 ` Wang, Lawrence (NSB - CN/Hangzhou)
2021-11-15 11:01 ` Andy Shevchenko
2021-11-16 1:43 ` Wang, Lawrence (NSB - CN/Hangzhou)
2021-11-29 19:28 ` Wolfram Sang
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