Re: [PATCH 2/2] serial: 8250_dw: Select U6_16550A for 64-byte FIFO

[sashiko-bot@kernel.org]

> From: Kryštof Černý <cleverline1mc@gmail.com>
> 
> DesignWare 8250 ports that describe their FIFO in the CPR register are
> always configured as PORT_16550A, regardless of the FIFO depth. On
> UARTs with a 64-byte FIFO, such as those on the Rockchip RK3328, this
> selects the 16-byte rxtrig_bytes table {1, 4, 8, 14}. The rx_trig_bytes
> sysfs attribute then reports 8 bytes while the hardware triggers at 32,
> and writes to it program the wrong trigger level.
> 
> Select PORT_U6_16550A when the CPR reports a 64-byte FIFO. Generic
> autoconfig already assigns this type to a 16550A with a 64-byte FIFO,
> and its rxtrig_bytes table matches the DesignWare FCR RT encoding.
> 
> The FIFO size, TX load size and capabilities are still taken from the
> CPR, and the default FCR value is the same for both types, so the
> hardware is programmed exactly as before. The port type reported to
> userspace changes from 16550A to U6_16550A.
> 
> Co-developed-by: Miroslav Ondra <ondra@faster.cz>
> Signed-off-by: Miroslav Ondra <ondra@faster.cz>
> Signed-off-by: Kryštof Černý <cleverline1mc@gmail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261109-8250-select-u6-64bit-v1-0-04bc8332fa34@gmail.com?part=2