Searched hist:"4516 d50a" (Results 1 – 2 of 2) sorted by relevance
/openbmc/linux/include/linux/ |
H A D | serial_8250.h | 4516d50a Thu Jan 22 11:24:30 CST 2015 Peter Hurley <peter@hurleysoftware.com> 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 <dianders@chromium.org> for the idea of using the scratch register canary to discover port power-down.
Cc: Doug Anderson <dianders@chromium.org> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 4516d50a Thu Jan 22 11:24:30 CST 2015 Peter Hurley <peter@hurleysoftware.com> 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 <dianders@chromium.org> for the idea of using the scratch register canary to discover port power-down. Cc: Doug Anderson <dianders@chromium.org> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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/openbmc/linux/drivers/tty/serial/8250/ |
H A D | 8250_core.c | 4516d50a Thu Jan 22 11:24:30 CST 2015 Peter Hurley <peter@hurleysoftware.com> 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 <dianders@chromium.org> for the idea of using the scratch register canary to discover port power-down.
Cc: Doug Anderson <dianders@chromium.org> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 4516d50a Thu Jan 22 11:24:30 CST 2015 Peter Hurley <peter@hurleysoftware.com> 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 <dianders@chromium.org> for the idea of using the scratch register canary to discover port power-down. Cc: Doug Anderson <dianders@chromium.org> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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