From: Peter Hurley Date: Thu, 22 Jan 2015 17:24:30 +0000 (-0500) Subject: serial: 8250: Use canary to restart console after suspend X-Git-Tag: omap-for-v4.1/prcm-dts-mfd-syscon-fix~82^2~17 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4516d50aabedbe5ae334155193e4d35c02390d9a;p=pandora-kernel.git serial: 8250: Use canary to restart console after suspend When using no_console_suspend, the serial console may be powered off anyway during system sleep. Upon resume, the port may be in its default power-on state, but is expected to continue console i/o before the device has received its pm callback. The resultant garbage i/o can cause all kinds of havoc on the remote end. Use the scratch register as a canary to discover if the console has been powered-off. Write a non-zero value to the scratch register at port suspend and reprogram the port before any console i/o if the scratch register != canary before port resume. This workaround is disabled for omap_8250 (which uses different divisor programming). Credit to Doug Anderson for the idea of using the scratch register canary to discover port power-down. Cc: Doug Anderson Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- Reading git-diff-tree failed