Date: Fri, 17 Aug 2018 10:26:56 -0600 From: Ian Lepore <ian@freebsd.org> To: Rajesh Kumar <rajfbsd@gmail.com>, freebsd-drivers@freebsd.org, freebsd-hackers@freebsd.org Subject: Re: Need a clarification regarding I2C bus frequency in FreeBSD Message-ID: <1534523216.27158.17.camel@freebsd.org> In-Reply-To: <CAAO%2BANOXwXAzJt%2BBZez6422jqKjrKPboSe_%2BudnOCWxYqE-=sQ@mail.gmail.com> References: <CAAO%2BANOXwXAzJt%2BBZez6422jqKjrKPboSe_%2BudnOCWxYqE-=sQ@mail.gmail.com>
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On Fri, 2018-08-17 at 11:48 +0530, Rajesh Kumar wrote: > Hi, > > I am trying to use the I2C designware controller driver available in > FreeBSD (ig4_iic.c) in our boards. > > Is there a clean way, I can set the I2C bus frequency from the controller > driver itself, rather than using device hints, FDT, tunables etc., > Something like, if the driver is loaded for our boards (identified using > the PCI or ACPI ID's), then the frequency of the I2C bus needs to be > hardcoded from driver itself. This is to avoid additional configs from the > config file. > > I tried adding a new interface "iicbus_set_frequency" (in line with > iicbus_get_frequency) and tried calling that from the ig4 driver after the > "iicbus" child is added. But, iicbus instance is created only after ig4 > driver is loaded. So, calling iicbus_set_frequency after child addition > leads to system panic (as there is no iicbus softc at this point). > > Let me know if you need any details. > > Thanks, > Rajesh. I don't really understand what you're asking for. The ig4_iic controller driver doesn't appear to support bus frequency settings at all, it just loads hard-coded values into the clock high/low registers and never changes them. If you want to locally modify the driver to run at a different hard-coded speed for your application, just change lines 589-592 in ig4_iic.c and continue to ignore the speed set by the bus driver when handling iicbus_reset. -- Ian
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