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由 Jeremy Kerr 提交于
This change adds a driver for the 16550-based Aspeed virtual UART device. We use a similar process to the of_serial driver for device probe, but expose some VUART-specific functions through sysfs too. The VUART is two UART 'front ends' connected by their FIFO (no actual serial line in between). One is on the BMC side (management controller) and one is on the host CPU side. This driver is for the BMC side. The sysfs files allow the BMC userspace, which owns the system configuration policy, to specify at what IO port and interrupt number the host side will appear to the host on the Host <-> BMC LPC bus. It could be different on a different system (though most of them use 3f8/4). OpenPOWER host firmware doesn't like it when the host-side of the VUART's FIFO is not drained. This driver only disables host TX discard mode when the port is in use. We set the VUART enabled bit when we bind to the device, and clear it on unbind. We don't want to do this on open/release, as the host may be using this bit to configure serial output modes, which is independent of whether the devices has been opened by BMC userspace. Signed-off-by: NJeremy Kerr <jk@ozlabs.org> Signed-off-by: NJoel Stanley <joel@jms.id.au> Acked-by: NRob Herring <robh@kernel.org> Reviewed-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org> Reviewed-by: NAndy Shevchenko <andy.shevchenko@gmail.com> Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
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