Re: [PATCH v6] serial: support for 16550A serial ports on LP-8x4x

Andy Shevchenko
2016-02-29T10:29:10Z

On Sat, 2016-02-27 at 19:14 +0300, Sergei Ianovich wrote:
> The patch adds support for 3 additional LP-8x4x built-in serial
> ports.
>
> The device can also host up to 8 extension cards with 4 serial ports
> on each card for a total of 35 ports. However, I don't have
> the hardware to test extension cards, so they are not supported, yet.

My comments below.
After addressing them:
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> +++ b/drivers/tty/serial/8250/8250_lp8841.c
> @@ -0,0 +1,166 @@
> +/*  linux/drivers/tty/serial/8250/8250_lp8841.c
> + *
> + *  Support for 16550A serial ports on ICP DAS LP-8841
> + *
> + *  Copyright (C) 2013 Sergei Ianovich <ynvich@gmail.com>
> + *
> + *  This program is free software; you can redistribute it and/or
> modify
> + *  it under the terms of the GNU General Public License version 2
> as
> + *  published by the Free Software Foundation.
> + */
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/irq.h>
> +#include <linux/module.h>
> +#include <linux/serial_8250.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +
> +struct lp8841_serial_data {
> + int line;
> + void *ios_mem;

__iomem

> +};

> + if (termios->c_cflag & CSTOPB)
> + len++;
> + if (termios->c_cflag & PARENB)
> + len++;
> + if (!(termios->c_cflag & PARODD))
> + len++;
> +#ifdef CMSPAR
> + if (termios->c_cflag & CMSPAR)
> + len++;
> +#endif
> +
> + len -= 9;

If you have 5 bit mode, no parity, 1/1.5 stop bits, you may end up with
negative value here. Am I right? If so, is it expected?

> + len &= 3;
> + len <<= 3;

> + writeb(len, data->ios_mem);
> +
> +}

> +static int lp8841_serial_probe(struct platform_device *pdev)
> +{
> + struct uart_8250_port uart = {};
> + struct lp8841_serial_data *data;
> + struct resource *mmres, *mires;
> + int ret;
> +
> + mmres = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + mires = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> + if (!mmres || !mires)
> + return -ENODEV;

No need to check mires here, devm_ioremap_resource() will take care
about.

> +
> + data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + data->ios_mem = devm_ioremap_resource(&pdev->dev, mires);
> + if (!data->ios_mem)
> + return -EFAULT;

You have to propagate the actual error code from
devm_ioremap_resource().

> +
> + uart.port.iotype = UPIO_MEM;
>

> + uart.port.mapbase = mmres->start;
> + uart.port.iobase = mmres->start;

I'm not sure about this. If you ask for UPIO_MEM why do you need to
fill iobase?
And I suppose iobase can't hold (at the end inb/outb calls) big port
numbers anyway (16 bit on x86, for example).

> + uart.port.regshift = 1;
> + uart.port.irq = platform_get_irq(pdev, 0);
> + uart.port.flags = UPF_IOREMAP;
> + uart.port.dev = &pdev->dev;
> + uart.port.uartclk = 14745600;
> + uart.port.set_termios = lp8841_serial_set_termios;
> + uart.port.private_data = data;
> +
> + ret = serial8250_register_8250_port(&uart);
> + if (ret < 0)
> + return ret;
> +
> + data->line = ret;
> +
> + platform_set_drvdata(pdev, data);
> +
> + return 0;
> +}
> +
> +static int lp8841_serial_remove(struct platform_device *pdev)
> +{
> + struct lp8841_serial_data *data =
> platform_get_drvdata(pdev);
> +
> + serial8250_unregister_port(data->line);
> +
> + return 0;
> +}
> +
> +static struct platform_driver lp8841_serial_driver = {
> + .probe          = lp8841_serial_probe,
> + .remove         = lp8841_serial_remove,
> +
> + .driver = {
> + .name = "uart-lp8841",
> + .of_match_table = lp8841_serial_dt_ids,
> + },
> +};

--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy