linux-kernel - Re: [PATCH V5 3/3] tty: serial: uartps: Add rs485 support to uartps driver

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Message-ID: <e8cf9ed3-e2d3-4764-b1c3-87e38e99b4a5@gmx.de>
Date:   Thu, 14 Dec 2023 10:00:00 +0100
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Manikanta Guntupalli <manikanta.guntupalli@....com>, git@....com,
        michal.simek@....com, gregkh@...uxfoundation.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, linux-serial@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        jirislaby@...nel.org, linux-arm-kernel@...ts.infradead.org
Cc:     radhey.shyam.pandey@....com, srinivas.goud@....com,
        shubhrajyoti.datta@....com, manion05gk@...il.com
Subject: Re: [PATCH V5 3/3] tty: serial: uartps: Add rs485 support to uartps
 driver


Hi,

On 13.12.23 14:00, Manikanta Guntupalli wrote:

>
> +/**
> + * cdns_rs485_rx_callback - Timer rx callback handler for rs485.
> + * @t: Handle to the timer list structure
> + */
> +static void cdns_rs485_rx_callback(struct timer_list *t)
> +{
> +	struct cdns_uart *cdns_uart = from_timer(cdns_uart, t, timer);
> +
> +	/*
> +	 * Default Rx should be setup, because Rx signaling path
> +	 * need to enable to receive data.
> +	 */
> +	cdns_rs485_rx_setup(cdns_uart);
> +}
> +
> +/**
> + * cdns_rs485_tx_callback - Timer tx callback handler for rs485.
> + * @t: Handle to the timer list structure
> + */
> +static void cdns_rs485_tx_callback(struct timer_list *t)
> +{
> +	struct cdns_uart *cdns_uart = from_timer(cdns_uart, t, timer);
> +
> +	cdns_uart_handle_tx(cdns_uart->port);

This is called without holding the port lock now. Are you sure the lock is not
needed? AFAIK the port lock is needed at least for accessing the circular
buffer.

> +
> +	/* Enable the TX Empty interrupt */
> +	writel(CDNS_UART_IXR_TXEMPTY, cdns_uart->port->membase + CDNS_UART_IER);
> +
> +	if (uart_circ_empty(&cdns_uart->port->state->xmit) ||
> +	    uart_tx_stopped(cdns_uart->port)) {
> +		timer_setup(&cdns_uart->timer, cdns_rs485_rx_callback, 0);
> +		mod_timer(&cdns_uart->timer, jiffies +
> +			  msecs_to_jiffies(cdns_uart->port->rs485.delay_rts_after_send));
> +	}
> +}

Regards,
Lino