Re: [PATCH v3 1/2] tty: serial: 8250: Add Mediatek UART driver

[Matthias Brugger]

2014-08-08 14:28 GMT+02:00 Tobias Klauser <tklauser@xxxxxxxxxx>:
> On 2014-08-08 at 13:32:03 +0200, Matthias Brugger <matthias.bgg@xxxxxxxxx> wrote:
>> This patch adds support for the UART block found on Mediatek SoCs.
>> The device has a highspeed register which influences the calcualtion of the
>> divisor. The chip lacks support for some baudrates. When requested, we set the
>> divisor to the next smaller baudrate and adjust the c_cflag accordingly.
>>
>> Signed-off-by: Matthias Brugger <matthias.bgg@xxxxxxxxx>
>> ---
>>  drivers/tty/serial/8250/8250_mtk.c |  296 ++++++++++++++++++++++++++++++++++++
>>  drivers/tty/serial/8250/Kconfig    |    7 +
>>  drivers/tty/serial/8250/Makefile   |    1 +
>>  3 files changed, 304 insertions(+)
>>  create mode 100644 drivers/tty/serial/8250/8250_mtk.c
>>
>> diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
>> new file mode 100644
>> index 0000000..d63080b
>> --- /dev/null
>> +++ b/drivers/tty/serial/8250/8250_mtk.c
>> @@ -0,0 +1,296 @@
>
> [...]
>
>> +static int mtk8250_probe(struct platform_device *pdev)
>> +{
>> +     struct uart_8250_port uart = {};
>> +     struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +     struct resource *irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
>> +     struct mtk8250_data *data;
>> +     int err;
>> +
>> +     if (!regs || !irq) {
>> +             dev_err(&pdev->dev, "no registers/irq defined\n");
>> +             return -EINVAL;
>> +     }
>> +
>> +     spin_lock_init(&uart.port.lock);
>> +     uart.port.mapbase = regs->start;
>> +     uart.port.irq = irq->start;
>> +     uart.port.pm = mtk8250_do_pm;
>> +     uart.port.type = PORT_16550;
>> +     uart.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT;
>> +     uart.port.dev = &pdev->dev;
>> +
>> +     uart.port.membase = devm_ioremap(&pdev->dev, regs->start,
>> +                                      resource_size(regs));
>> +     if (!uart.port.membase)
>> +             return -ENOMEM;
>
> You can use devm_ioremap_resource here and get rid of the check for
> !regs above, since devm_ioremap_resource already does that.
>
>         regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>
>         ...
>
>         uart.port.membase = devm_ioremap_resource(&pdev->dev, regs);
>         if (IS_ERR(uart.port.membase))
>                 return PTR_ERR(uart.port.membase);
>

devm_ioremap_resource creates a busy resource region in the
iomem_resource. This leads the UART to silently fail.
I suppose that's why 8250_dw.c uses devm_ioremap instead of
devm_ioremap_resource. The 8250_dw has the same issue.

Thanks,
Matthias

>> +
>> +     data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
>> +     if (!data)
>> +             return -ENOMEM;
>
> I'd suggest to move this kzalloc and the ioremap before the uart.port
> initialization part above, so you can error out early in case of any
> failure.
>
>> +
>> +     uart.port.iotype = UPIO_MEM32;
>> +     uart.port.regshift = 2;
>> +     uart.port.private_data = data;
>> +     uart.port.set_termios = mtk8250_set_termios;
>> +
>> +     if (pdev->dev.of_node) {
>> +             err = mtk8250_probe_of(&uart.port, data);
>> +             if (err)
>> +                     return err;
>> +     } else
>> +             return -ENODEV;
>
> This could also be moved up, directly below devm_kzalloc.
>
>> +
>> +     /* Disable Rate Fix function */
>> +     writel(0x0, uart.port.membase +
>> +                     (MTK_UART_RATE_FIX << uart.port.regshift));
>> +
>> +     data->line = serial8250_register_8250_port(&uart);
>> +     if (data->line < 0)
>> +             return data->line;
>> +
>> +     platform_set_drvdata(pdev, data);
>> +
>> +     pm_runtime_set_active(&pdev->dev);
>> +     pm_runtime_enable(&pdev->dev);
>> +
>> +     return 0;
>> +}
>> +
>> +static int mtk8250_remove(struct platform_device *pdev)
>> +{
>> +     struct mtk8250_data *data = platform_get_drvdata(pdev);
>> +
>> +     pm_runtime_get_sync(&pdev->dev);
>> +
>> +     serial8250_unregister_port(data->line);
>> +     if (!IS_ERR(data->clk)) {
>> +             clk_disable_unprepare(data->clk);
>> +             clk_put(data->clk);
>> +     }
>> +
>> +     pm_runtime_disable(&pdev->dev);
>> +     pm_runtime_put_noidle(&pdev->dev);
>> +     return 0;
>> +}
>> +
>> +#ifdef CONFIG_PM_SLEEP
>> +static int mtk8250_suspend(struct device *dev)
>> +{
>> +     struct mtk8250_data *data = dev_get_drvdata(dev);
>> +
>> +     serial8250_suspend_port(data->line);
>> +
>> +     return 0;
>> +}
>> +
>> +static int mtk8250_resume(struct device *dev)
>> +{
>> +     struct mtk8250_data *data = dev_get_drvdata(dev);
>> +
>> +     serial8250_resume_port(data->line);
>> +
>> +     return 0;
>> +}
>> +#endif /* CONFIG_PM_SLEEP */
>> +
>> +#ifdef CONFIG_PM_RUNTIME
>> +static int mtk8250_runtime_suspend(struct device *dev)
>> +{
>> +     struct mtk8250_data *data = dev_get_drvdata(dev);
>> +
>> +     if (!IS_ERR(data->clk))
>> +             clk_disable_unprepare(data->clk);
>> +
>> +     return 0;
>> +}
>> +
>> +static int mtk8250_runtime_resume(struct device *dev)
>> +{
>> +     struct mtk8250_data *data = dev_get_drvdata(dev);
>> +
>> +     if (!IS_ERR(data->clk))
>> +             clk_prepare_enable(data->clk);
>> +
>> +     return 0;
>> +}
>> +#endif
>> +
>> +static const struct dev_pm_ops mtk8250_pm_ops = {
>> +     SET_SYSTEM_SLEEP_PM_OPS(mtk8250_suspend, mtk8250_resume)
>> +     SET_RUNTIME_PM_OPS(mtk8250_runtime_suspend, mtk8250_runtime_resume,
>> +                             NULL)
>> +};
>> +
>> +static const struct of_device_id mtk8250_of_match[] = {
>> +     { .compatible = "mediatek,mt6577-uart" },
>> +     { /* Sentinel */ }
>> +};
>> +MODULE_DEVICE_TABLE(of, mtk8250_of_match);
>> +
>> +static struct platform_driver mtk8250_platform_driver = {
>> +     .driver = {
>> +             .name           = "mt6577-uart",
>> +             .owner          = THIS_MODULE,
>
> This doesn't need to be set here,
> module_platform_driver/platform_driver_register take care of setting it.
>
>> +             .pm             = &mtk8250_pm_ops,
>> +             .of_match_table = mtk8250_of_match,
>> +     },
>> +     .probe                  = mtk8250_probe,
>> +     .remove                 = mtk8250_remove,
>> +};
>> +module_platform_driver(mtk8250_platform_driver);
>> +
>> +MODULE_AUTHOR("Matthias Brugger");
>> +MODULE_LICENSE("GPL");
>> +MODULE_DESCRIPTION("Mediatek 8250 serial port driver");



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