linux-kernel - Re: [PATCH v5 2/2] serial:sunplus-uart:Add Sunplus SoC UART Driver

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Message-ID: <61fefc9d-643d-ca31-9a6d-d2e10cd060bb@kernel.org>
Date:   Mon, 13 Dec 2021 08:47:11 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Hammer Hsieh <hammerh0314@...il.com>, gregkh@...uxfoundation.org,
        robh+dt@...nel.org, linux-serial@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        p.zabel@...gutronix.de
Cc:     wells.lu@...plus.com, Hammer Hsieh <hammer.hsieh@...plus.com>
Subject: Re: [PATCH v5 2/2] serial:sunplus-uart:Add Sunplus SoC UART Driver

On 13. 12. 21, 8:10, Hammer Hsieh wrote:
> Add Sunplus SoC UART Driver
> 
> Signed-off-by: Hammer Hsieh <hammer.hsieh@...plus.com>

...

> --- /dev/null
> +++ b/drivers/tty/serial/sunplus-uart.c

...

> +static void receive_chars(struct uart_port *port)
> +{
> +	unsigned int lsr = readl(port->membase + SUP_UART_LSR);
> +	unsigned int ch, flag;
> +
> +	do {
> +		ch = readl(port->membase + SUP_UART_DATA);
> +		flag = TTY_NORMAL;
> +		port->icount.rx++;
> +
> +		if (unlikely(lsr & SUP_UART_LSR_BRK_ERROR_BITS)) {
> +			if (lsr & SUP_UART_LSR_BC) {
> +				lsr &= ~(SUP_UART_LSR_FE | SUP_UART_LSR_PE);
> +				port->icount.brk++;
> +				if (uart_handle_break(port))
> +					goto ignore_char;
> +			} else if (lsr & SUP_UART_LSR_PE) {
> +				port->icount.parity++;
> +			} else if (lsr & SUP_UART_LSR_FE) {
> +				port->icount.frame++;
> +			}
> +
> +			if (lsr & SUP_UART_LSR_OE)
> +				port->icount.overrun++;
> +
> +			if (lsr & SUP_UART_LSR_BC)
> +				flag = TTY_BREAK;
> +			else if (lsr & SUP_UART_LSR_PE)
> +				flag = TTY_PARITY;
> +			else if (lsr & SUP_UART_LSR_FE)
> +				flag = TTY_FRAME;

Why do you handle these separately and not above?

> +		}
> +
> +		if (port->ignore_status_mask & SUP_DUMMY_READ)
> +			goto ignore_char;
> +
> +		if (uart_handle_sysrq_char(port, ch))
> +			goto ignore_char;
> +
> +		uart_insert_char(port, lsr, SUP_UART_LSR_OE, ch, flag);
> +
> +ignore_char:
> +		lsr = readl(port->membase + SUP_UART_LSR);
> +	} while (lsr & SUP_UART_LSR_RX);
> +
> +	tty_flip_buffer_push(&port->state->port);
> +}
> +
> +static irqreturn_t sunplus_uart_irq(int irq, void *args)
> +{
> +	struct uart_port *port = (struct uart_port *)args;

No need to cast here.

> +	unsigned int isc = readl(port->membase + SUP_UART_ISC);

Shouldn't this be under the spinlock?

And "if (!isc) return IRQ_NONE"?

> +	spin_lock(&port->lock);
> +
> +	if (isc & SUP_UART_ISC_RX)
> +		receive_chars(port);
> +
> +	if (isc & SUP_UART_ISC_TX)
> +		transmit_chars(port);
> +
> +	spin_unlock(&port->lock);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int sunplus_startup(struct uart_port *port)
> +{
> +	unsigned long flags;
> +	unsigned int isc;
> +	int ret;
> +
> +	ret = request_irq(port->irq, sunplus_uart_irq, 0, "sunplus_uart", port);

Cannot the interrupt be shared?

> +	if (ret)
> +		return ret;
> +
> +	spin_lock_irqsave(&port->lock, flags);
> +
> +	isc |= SUP_UART_ISC_RXM;
> +	writel(isc, port->membase + SUP_UART_ISC);
> +
> +	spin_unlock_irqrestore(&port->lock, flags);
> +
> +	return 0;
> +}
> +
> +static void sunplus_shutdown(struct uart_port *port)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&port->lock, flags);
> +	writel(0, port->membase + SUP_UART_ISC);

What bus is this -- posting?

> +	spin_unlock_irqrestore(&port->lock, flags);
> +
> +	free_irq(port->irq, port);
> +}

...

> +static void sunplus_release_port(struct uart_port *port)
> +{
> +}
> +
> +static int sunplus_request_port(struct uart_port *port)
> +{
> +	return 0;
> +}

These two are optional -- no need to provide them.

regards,
-- 
js
suse labs