Re: [PATCH tty v1 41/74] serial: msm: Use port lock wrappers

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On Thu, Sep 14, 2023 at 08:43:58PM +0206, John Ogness wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> When a serial port is used for kernel console output, then all
> modifications to the UART registers which are done from other contexts,
> e.g. getty, termios, are interference points for the kernel console.
> So far this has been ignored and the printk output is based on the
> principle of hope. The rework of the console infrastructure which aims to
> support threaded and atomic consoles, requires to mark sections which
> modify the UART registers as unsafe. This allows the atomic write function
> to make informed decisions and eventually to restore operational state. It
> also allows to prevent the regular UART code from modifying UART registers
> while printk output is in progress.
> All modifications of UART registers are guarded by the UART port lock,
> which provides an obvious synchronization point with the console
> infrastructure.
> To avoid adding this functionality to all UART drivers, wrap the
> spin_[un]lock*() invocations for uart_port::lock into helper functions
> which just contain the spin_[un]lock*() invocations for now. In a
> subsequent step these helpers will gain the console synchronization
> mechanisms.
> Converted with coccinelle. No functional change.
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Reviewed-by: Bjorn Andersson <quic_bjorande@xxxxxxxxxxx>


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