Date: Wed, 8 Mar 2017 11:35:21 -0800 (PST) From: "Rodney W. Grimes" <freebsd@pdx.rh.CN85.dnsmgr.net> To: Ian Lepore <ian@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r314917 - head/sys/dev/uart Message-ID: <201703081935.v28JZLTv002380@pdx.rh.CN85.dnsmgr.net> In-Reply-To: <201703081853.v28IrWhm099535@repo.freebsd.org>
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[ Charset UTF-8 unsupported, converting... ] > Author: ian > Date: Wed Mar 8 18:53:32 2017 > New Revision: 314917 > URL: https://svnweb.freebsd.org/changeset/base/314917 > > Log: > Handle fifo size differences between older and newer revs of pl011 hardware. > > Starting with rev 5 (which is inexplicably indicated by a version number > of '3' in the Peripheral ID register), the pl011 doubled the size of the > rx and tx fifos, to 32 bytes, so read the ID register and set the size > variables in the softc accordingly. > > An interesting wrinkle in this otherwise-simple concept is that the > bcm2835 SoC, used in Raspberry Pi systems among others, has the rev 5 > pl011 hardware, but somehow also has the older 16-byte fifos. We check > the FDT data to see if the hardware is part of a bcm283x system and use > the smaller size if so. The chip compiler probably has a parameter to set fifo depth, this would normally be independent of the IP revision. -- Rod Grimes rgrimes@freebsd.org
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