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Date: Tue, 12 Aug 2014 15:31:51 +0200
From: Matthias Brugger <matthias.bgg@...il.com>
To: Tobias Klauser <tklauser@...tanz.ch>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Randy Dunlap <rdunlap@...radead.org>,
Greg KH <gregkh@...uxfoundation.org>, jslaby@...e.cz,
Grant Likely <grant.likely@...aro.org>,
Alan Cox <alan@...ux.intel.com>,
Varka Bhadram <varkabhadram@...il.com>,
Heiko Stübner <heiko@...ech.de>,
Yingjoe Chen <yingjoe.chen@...il.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
linux-serial@...r.kernel.org
Subject: Re: [PATCH v3 1/2] tty: serial: 8250: Add Mediatek UART driver
2014-08-08 14:28 GMT+02:00 Tobias Klauser <tklauser@...tanz.ch>:
> On 2014-08-08 at 13:32:03 +0200, Matthias Brugger <matthias.bgg@...il.com> 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@...il.com>
>> ---
>> 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");
--
motzblog.wordpress.com
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