Date: Sun, 19 Aug 2018 12:29:07 +0200 From: Emmanuel Vadot <manu@bidouilliste.com> To: Daniel Braniss <danny@cs.huji.ac.il> Cc: Ian Lepore <ian@freebsd.org>, Rajesh Kumar <rajfbsd@gmail.com>, freebsd-hackers@freebsd.org, freebsd-drivers@freebsd.org Subject: Re: Need a clarification regarding I2C bus frequency in FreeBSD Message-ID: <20180819122907.8c9306a0a307b9887443e818@bidouilliste.com> In-Reply-To: <3C2D99A1-DC1C-4915-81DE-7F9D48AAB10E@cs.huji.ac.il> References: <CAAO%2BANOXwXAzJt%2BBZez6422jqKjrKPboSe_%2BudnOCWxYqE-=sQ@mail.gmail.com> <1534523216.27158.17.camel@freebsd.org> <3C2D99A1-DC1C-4915-81DE-7F9D48AAB10E@cs.huji.ac.il>
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On Sun, 19 Aug 2018 13:11:15 +0300 Daniel Braniss <danny@cs.huji.ac.il> wrote: >=20 >=20 > > On 17 Aug 2018, at 19:26, Ian Lepore <ian@freebsd.org> wrote: > >=20 > > On Fri, 2018-08-17 at 11:48 +0530, Rajesh Kumar wrote: > >> Hi, > >>=20 > >> I am trying to use the I2C designware controller driver available in > >> FreeBSD (ig4_iic.c) in our boards. > >>=20 > >> Is there a clean way, I can set the I2C bus frequency from the control= ler > >> driver itself, rather than using device hints, FDT, tunables etc., > >> Something like, if the driver is loaded for our boards (identified usi= ng > >> 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. > >>=20 > >> 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 i= g4 > >> driver is loaded. So, calling iicbus_set_frequency after child addition > >> leads to system panic (as there is no iicbus softc at this point). > >>=20 > >> Let me know if you need any details. > >>=20 > >> Thanks, > >> Rajesh. > >=20 > > 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. > >=20 >=20 > on the arm/allwinner it?s set at 100Khz, and though there are sysctls to = change it, > it?s ignored :-) It is set at whatever frequency the dts set it and if there is no frequency in the dts it fallback to 100Khz. twsi needs to support IICBUS_GET_FREQUENCY though, the main reason I never really touched twsi is because the same driver is used on Marvell SoC with hackish support for the clocks. Now that I have a Marvell board with this i2c controller I'll probably rewrite this driver. > I could change this, but is there some hidden reason that it?s so? >=20 > danny >=20 > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" --=20 Emmanuel Vadot <manu@bidouilliste.com> <manu@freebsd.org>
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