Date:   Tue, 24 Oct 2023 07:54:35 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Brenda Streiff <brenda.streiff@...com>
Cc:     Gratian Crisan <gratian.crisan@...com>,
        Jason Smith <jason.smith@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v6 tty-next 2/2] serial: 8250: add driver for NI UARTs

On 23. 10. 23, 23:04, Brenda Streiff wrote:
> The National Instruments (NI) 16550 is a 16550-like UART with larger
> FIFOs and embedded RS-232/RS-485 transceiver control circuitry. This
> patch adds a driver that can operate this UART, which is used for
> onboard serial ports in several NI embedded controller designs.
> 
> Portions of this driver were originally written by Jaeden Amero and
> Karthik Manamcheri, with extensive cleanups and refactors since.

...

> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_ni.c
...
> +static int ni16550_probe(struct platform_device *pdev)
> +{
> +	const struct ni16550_device_info *info;
> +	struct device *dev = &pdev->dev;
> +	struct uart_8250_port uart = {};
> +	unsigned int prescaler = 0;
> +	struct ni16550_data *data;
> +	const char *portmode;
> +	int txfifosz, rxfifosz;

Why not unsigned?

> +	int rs232_property;

bool

> +	int ret;
> +	int irq;
> +
> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	spin_lock_init(&uart.port.lock);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return irq;
> +
> +	ret = ni16550_get_regs(pdev, &uart.port);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* early setup so that serial_in()/serial_out() work */
> +	serial8250_set_defaults(&uart);
> +
> +	info = device_get_match_data(dev);
> +
> +	uart.port.dev		= dev;
> +	uart.port.irq		= irq;
> +	uart.port.irqflags	= IRQF_SHARED;
> +	uart.port.flags		= UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
> +					| UPF_FIXED_PORT | UPF_FIXED_TYPE;
> +	uart.port.startup	= ni16550_port_startup;
> +	uart.port.shutdown	= ni16550_port_shutdown;
> +
> +	/*
> +	 * Hardware instantiation of FIFO sizes are held in registers.
> +	 */
> +	txfifosz = ni16550_read_fifo_size(&uart, NI16550_TFS_OFFSET);
> +	rxfifosz = ni16550_read_fifo_size(&uart, NI16550_RFS_OFFSET);
> +
> +	dev_dbg(dev, "NI 16550 has TX FIFO size %d, RX FIFO size %d\n",
> +		txfifosz, rxfifosz);
> +
> +	uart.port.type		= PORT_16550A;
> +	uart.port.fifosize	= txfifosz;
> +	uart.tx_loadsz		= txfifosz;
> +	uart.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10;
> +	uart.capabilities	= UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR;
> +
> +	/*
> +	 * Declaration of the base clock frequency can come from one of:
> +	 * - static declaration in this driver (for older ACPI IDs)
> +	 * - a "clock-frquency" ACPI or OF device property
> +	 * - an associated OF clock definition
> +	 */
> +	if (info->uartclk)
> +		uart.port.uartclk = info->uartclk;
> +	if (device_property_read_u32(dev, "clock-frequency",
> +				     &uart.port.uartclk)) {
> +		data->clk = devm_clk_get_optional_enabled(dev, NULL);
> +		if (data->clk)

!IS_ERR(data->clk)

> +			uart.port.uartclk = clk_get_rate(data->clk);
> +	}
> +
> +	if (!uart.port.uartclk) {
> +		dev_err(dev, "unable to determine clock frequency!\n");
> +		ret = -ENODEV;
> +		goto err;
> +	}
> +
> +	if (info->prescaler)
> +		prescaler = info->prescaler;
> +	device_property_read_u32(dev, "clock-prescaler", &prescaler);
> +
> +	if (prescaler != 0) {
> +		uart.port.set_mctrl = ni16550_set_mctrl;
> +		ni16550_config_prescaler(&uart, (u8)prescaler);
> +	}
> +
> +	/*
> +	 * The determination of whether or not this is an RS-485 or RS-232 port
> +	 * can come from a device property (if present), or it can come from
> +	 * the PMR (if present), and otherwise we're solely an RS-485 port.
> +	 *
> +	 * This is a device-specific property, and thus has a vendor-prefixed
> +	 * "ni,serial-port-mode" form as a devicetree binding. However, there
> +	 * are old devices in the field using "transceiver" as an ACPI device
> +	 * property, so we have to check for that as well.
> +	 */
> +	if (!device_property_read_string(dev, "ni,serial-port-mode", &portmode) ||
> +	    !device_property_read_string(dev, "transceiver", &portmode)) {
> +		rs232_property = strncmp(portmode, "RS-232", 6) == 0;
> +
> +		dev_dbg(dev, "port is in %s mode (via device property)",

\n missing here and there.

> +			rs232_property ? "RS-232" : "RS-485");
> +	} else if (info->flags & NI_HAS_PMR) {
> +		rs232_property = is_pmr_rs232_mode(&uart);
> +
> +		dev_dbg(dev, "port is in %s mode (via PMR)",
> +			rs232_property ? "RS-232" : "RS-485");
> +	} else {
> +		rs232_property = 0;
> +
> +		dev_dbg(dev, "port is fixed as RS-485");
> +	}
> +
> +	if (!rs232_property) {
> +		/*
> +		 * Neither the 'transceiver' property nor the PMR indicate
> +		 * that this is an RS-232 port, so it must be an RS-485 one.
> +		 */
> +		ni16550_rs485_setup(&uart.port);
> +	}
> +
> +	ret = serial8250_register_8250_port(&uart);
> +	if (ret < 0)
> +		goto err;
> +	data->line = ret;
> +
> +	platform_set_drvdata(pdev, data);
> +	return 0;
> +
> +err:
> +	clk_disable_unprepare(data->clk);

But you use devm_?

> +	return ret;
> +}
> +
> +static int ni16550_remove(struct platform_device *pdev)
> +{
> +	struct ni16550_data *data = platform_get_drvdata(pdev);
> +
> +	clk_disable_unprepare(data->clk);
> +	serial8250_unregister_port(data->line);

This should be likely inverted. But I don't know if it matters here at all.

Actually, devm_ again, so the first is unnecessary?

> +	return 0;
> +}
...
> +MODULE_AUTHOR("Jaeden Amero <jaeden.amero@...com>");
> +MODULE_AUTHOR("Karthik Manamcheri <karthik.manamcheri@...com>");

Do the addresses work? Why not CC them?

thanks,
-- 
js
suse labs

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