Re: [PATCH v4 4/7] serial: sh-sci: Do not kick TX from sci_er_interrupt() on RSCI

[sashiko-bot@kernel.org]

> On RSCI, the receive error interrupt (ERI) has its own dedicated
> interrupt line and status flags cleared via the write-only CFCLR
> register, with no hardware interaction with transmission.
> 
> Calling sci_tx_interrupt() from sci_er_interrupt() on RSCI is
> unnecessary and causes rsci_transmit_chars() to run in invalid TX
> states:
> - If an RX error occurs while TX is idle (CCR0.TE == 0 and CSR.TDRE == 1)
>   and xmit_fifo is empty, rsci_transmit_chars() sets CCR0.TEIE while
>   CSR.TEND is 1, triggering a spurious TEI interrupt.
> - If an RX error occurs while the hardware TX FIFO is draining
>   (CSR.TDRE == 0) after xmit_fifo was flushed, rsci_transmit_chars()
>   clears CCR0.TIE without setting CCR0.TEIE, leaving CCR0.TE set after
>   the hardware FIFO drains and stalling subsequent transmissions.
> 
> Skip calling sci_tx_interrupt() in sci_er_interrupt() for RSCI ports.
> 
> Fixes: 0666e3fe95ab ("serial: sh-sci: Add support for RZ/T2H SCI")
> Cc: stable@vger.kernel.org
> Signed-off-by: Diogo Ivo <diogo.ivo.sx@renesas.com>

Sashiko has reviewed this patch and found no issues.

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