linux-kernel - Re: [PATCH v2] serial:xilinx_uartps:fix rs485 delay_rts_after

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Message-ID: <CAKfKVtEUj3=mt8FaU21zF5ZOqatzCAebW8R32f5E57VmyTtUbw@mail.gmail.com>
Date: Wed, 14 Jan 2026 10:08:55 +0530
From: Shubhrajyoti Datta <shubhrajyoti.datta@...il.com>
To: "j.turek" <jakub.turek@...ta.tech>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org, michal.simek@....com, 
	namcao@...utronix.de, tglx@...utronix.de, zack.rusin@...adcom.com, 
	sean.anderson@...ux.dev, hshah@...ado.com, linux-serial@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] serial:xilinx_uartps:fix rs485 delay_rts_after_send

On Sun, Dec 21, 2025 at 4:03 PM j.turek <jakub.turek@...ta.tech> wrote:
>
> RTS line control with delay should be triggered when there is no more bytes
> in kfifo and hardware buffer is empty. Without this patch RTS control is
> scheduled right after feeding hardware buffer and this is too early.
> RTS line may change state before hardware buffer is empty.
> With this patch delayed RTS state change is triggered when function
> cdns_uart_handle_tx is called from cdns_uart_isr on CDNS_UART_IXR_TXEMPTY
> exactly when hardware completed transmission
>
> Signed-off-by: Jakub Turek  <jakub.turek@...ta.tech>
>
> Fixes: fccc9d9233f9 ("tty: serial: uartps: Add rs485 support to uartps driver")


Reviewed-by: Shubhrajyoti Datta <shubhrajyoti.datta@....com>