| Message ID | 1452344854-2576-3-git-send-email-kernel@martin.sperl.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Martin, Am 09.01.2016 um 14:07 schrieb kernel@martin.sperl.org: > From: Martin Sperl <kernel@martin.sperl.org> > > The bcm2835 SOC contains an auxiliary uart, which is very close > to the ns16550 with some differences. > > The big difference is that the uart HW is not using an internal divider > of 16 but 8, which results in an effictive baud-rate being twice > the requested baud-rate. > > This driver handles this device correctly and handles the difference in > the HW divider by scaling up the clock ba a factor of 2. > > The approach to write a separate (wrapper) driver instead of using a > multiplying clock and "ns16550" as compatibility in the device-tree > has been recommended by Stephen Warren. > > Signed-off-by: Martin Sperl <kernel@martin.sperl.org> > --- > drivers/tty/serial/8250/8250_bcm2835aux.c | 143 +++++++++++++++++++++++++++++ > drivers/tty/serial/8250/Kconfig | 8 ++ > drivers/tty/serial/8250/Makefile | 1 + > 3 files changed, 152 insertions(+) > create mode 100644 drivers/tty/serial/8250/8250_bcm2835aux.c > > diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c > new file mode 100644 > index 0000000..718c357 > --- /dev/null > +++ b/drivers/tty/serial/8250/8250_bcm2835aux.c > @@ -0,0 +1,143 @@ > +/* > + * Serial port driver for BCM2835AUX UART > + * > + * Copyright (C) 2016 Martin Sperl <kernel@martin.sperl.org> > + * > + * Based on 8250_lpc18xx.c: > + * Copyright (C) 2015 Joachim Eastwood <manabian@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/clk.h> > +#include <linux/io.h> > +#include <linux/module.h> > +#include <linux/of.h> > +#include <linux/platform_device.h> > + > +#include "8250.h" > + > +struct bcm2835aux_data { > + struct uart_8250_port uart; > + struct clk *clk; > +}; > + > +static int bcm2835aux_serial_probe(struct platform_device *pdev) > +{ > + struct bcm2835aux_data *data; > + struct resource *res; > + int ret; > + > + /* allocate the custom structure */ > + data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL); > + if (!data) > + return -ENOMEM; > + > + /* initialize data */ > + spin_lock_init(&data->uart.port.lock); > + data->uart.port.dev = &pdev->dev; > + data->uart.port.regshift = 2; > + data->uart.port.type = PORT_16550; > + data->uart.port.iotype = UPIO_MEM; > + data->uart.port.fifosize = 8; data->uart.capabilities = UART_CAP_FIFO; ? > + data->uart.port.flags = UPF_SHARE_IRQ | > + UPF_FIXED_PORT | > + UPF_FIXED_TYPE | > + UPF_SKIP_TEST; > + > + /* get the clock - this also enables the HW */ > + data->clk = devm_clk_get(&pdev->dev, NULL); > + ret = PTR_ERR_OR_ZERO(data->clk); > + if (ret) { > + dev_err(&pdev->dev, "could not get clk: %d\n", ret); > + return ret; > + } > + > + /* get the interrupt */ > + data->uart.port.irq = platform_get_irq(pdev, 0); > + if (data->uart.port.irq < 0) { > + dev_err(&pdev->dev, "irq not found - %i", > + data->uart.port.irq); > + return data->uart.port.irq; > + } > + > + /* map the main registers */ > + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); > + if (!res) { > + dev_err(&pdev->dev, "memory resource not found"); > + return -EINVAL; > + } > + data->uart.port.membase = devm_ioremap_resource(&pdev->dev, res); > + ret = PTR_ERR_OR_ZERO(data->uart.port.membase); > + if (ret) > + return ret; > + > + /* Check for a fixed line number */ > + ret = of_alias_get_id(pdev->dev.of_node, "serial"); > + if (ret >= 0) > + data->uart.port.line = ret; > + > + /* enable the clock as a last step */ > + ret = clk_prepare_enable(data->clk); > + if (ret) { > + dev_err(&pdev->dev, "unable to enable uart clock\n"); > + return ret; > + } > + > + /* the HW-clock divider for bcm2835aux is 8, > + * but 8250 expects a divider of 16, > + * so we have to multiply the actual clock by 2 > + * to get identical baudrates. > + */ > + data->uart.port.uartclk = clk_get_rate(data->clk) * 2; > + > + /* register the port */ > + ret = serial8250_register_8250_port(&data->uart); > + if (ret < 0) { > + dev_err(&pdev->dev, > + "unable to register 8250 port - %d\n", ret); This should fit in one line. > + goto dis_clk; > + } > + data->uart.port.line = ret; This looks wrong because it overwrites the result of of_alias_get_id. Either you store it in a new member of bcm2835aux_data or drop the assignment. > + > + platform_set_drvdata(pdev, data); > + > + return 0; > + > +dis_clk: > + clk_disable_unprepare(data->clk); > + return ret; > +} > + > +static int bcm2835aux_serial_remove(struct platform_device *pdev) > +{ > + struct bcm2835aux_data *data = platform_get_drvdata(pdev); > + > + serial8250_unregister_port(data->uart.port.line); > + clk_disable_unprepare(data->clk); > + > + return 0; > +} > + > +static const struct of_device_id bcm2835aux_serial_match[] = { > + { .compatible = "brcm,bcm2835-aux-uart" }, > + { }, > +}; > +MODULE_DEVICE_TABLE(of, bcm2835aux_serial_match); > + > +static struct platform_driver bcm2835aux_serial_driver = { > + .driver = { > + .name = "bcm2835-aux-uart", > + .of_match_table = bcm2835aux_serial_match, > + }, > + .probe = bcm2835aux_serial_probe, > + .remove = bcm2835aux_serial_remove, > +}; > +module_platform_driver(bcm2835aux_serial_driver); > + > +MODULE_DESCRIPTION("BCM2835 auxiliar UART driver"); > +MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>"); > +MODULE_LICENSE("GPL v2"); > diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig > index 6412f14..105aa19 100644 > --- a/drivers/tty/serial/8250/Kconfig > +++ b/drivers/tty/serial/8250/Kconfig > @@ -272,6 +272,14 @@ config SERIAL_8250_ACORN > system, say Y to this option. The driver can handle 1, 2, or 3 port > cards. If unsure, say N. > > +config SERIAL_8250_BCM2835AUX > + tristate "BCM2835 auxiliar uart support" BCM2835 auxiliary mini UART support > + depends on ARCH_BCM2835 || COMPILE_TEST > + depends on SERIAL_8250 && SERIAL_8250_SHARE_IRQ > + help > + support for the BCM2835 auxiliar uart. auxiliary UART Since it's a mini UART it would be helpful to write down the limitiations here. > + If unsure, say N. > + > config SERIAL_8250_FSL > bool > depends on SERIAL_8250_CONSOLE >
>>>>> "kernel" == kernel <kernel@martin.sperl.org> writes: > From: Martin Sperl <kernel@martin.sperl.org> > The bcm2835 SOC contains an auxiliary uart, which is very close > to the ns16550 with some differences. > The big difference is that the uart HW is not using an internal divider > of 16 but 8, which results in an effictive baud-rate being twice > the requested baud-rate. > This driver handles this device correctly and handles the difference in > the HW divider by scaling up the clock ba a factor of 2. s/ba/by/
diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c new file mode 100644 index 0000000..718c357 --- /dev/null +++ b/drivers/tty/serial/8250/8250_bcm2835aux.c @@ -0,0 +1,143 @@ +/* + * Serial port driver for BCM2835AUX UART + * + * Copyright (C) 2016 Martin Sperl <kernel@martin.sperl.org> + * + * Based on 8250_lpc18xx.c: + * Copyright (C) 2015 Joachim Eastwood <manabian@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/clk.h> +#include <linux/io.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/platform_device.h> + +#include "8250.h" + +struct bcm2835aux_data { + struct uart_8250_port uart; + struct clk *clk; +}; + +static int bcm2835aux_serial_probe(struct platform_device *pdev) +{ + struct bcm2835aux_data *data; + struct resource *res; + int ret; + + /* allocate the custom structure */ + data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL); + if (!data) + return -ENOMEM; + + /* initialize data */ + spin_lock_init(&data->uart.port.lock); + data->uart.port.dev = &pdev->dev; + data->uart.port.regshift = 2; + data->uart.port.type = PORT_16550; + data->uart.port.iotype = UPIO_MEM; + data->uart.port.fifosize = 8; + data->uart.port.flags = UPF_SHARE_IRQ | + UPF_FIXED_PORT | + UPF_FIXED_TYPE | + UPF_SKIP_TEST; + + /* get the clock - this also enables the HW */ + data->clk = devm_clk_get(&pdev->dev, NULL); + ret = PTR_ERR_OR_ZERO(data->clk); + if (ret) { + dev_err(&pdev->dev, "could not get clk: %d\n", ret); + return ret; + } + + /* get the interrupt */ + data->uart.port.irq = platform_get_irq(pdev, 0); + if (data->uart.port.irq < 0) { + dev_err(&pdev->dev, "irq not found - %i", + data->uart.port.irq); + return data->uart.port.irq; + } + + /* map the main registers */ + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + if (!res) { + dev_err(&pdev->dev, "memory resource not found"); + return -EINVAL; + } + data->uart.port.membase = devm_ioremap_resource(&pdev->dev, res); + ret = PTR_ERR_OR_ZERO(data->uart.port.membase); + if (ret) + return ret; + + /* Check for a fixed line number */ + ret = of_alias_get_id(pdev->dev.of_node, "serial"); + if (ret >= 0) + data->uart.port.line = ret; + + /* enable the clock as a last step */ + ret = clk_prepare_enable(data->clk); + if (ret) { + dev_err(&pdev->dev, "unable to enable uart clock\n"); + return ret; + } + + /* the HW-clock divider for bcm2835aux is 8, + * but 8250 expects a divider of 16, + * so we have to multiply the actual clock by 2 + * to get identical baudrates. + */ + data->uart.port.uartclk = clk_get_rate(data->clk) * 2; + + /* register the port */ + ret = serial8250_register_8250_port(&data->uart); + if (ret < 0) { + dev_err(&pdev->dev, + "unable to register 8250 port - %d\n", ret); + goto dis_clk; + } + data->uart.port.line = ret; + + platform_set_drvdata(pdev, data); + + return 0; + +dis_clk: + clk_disable_unprepare(data->clk); + return ret; +} + +static int bcm2835aux_serial_remove(struct platform_device *pdev) +{ + struct bcm2835aux_data *data = platform_get_drvdata(pdev); + + serial8250_unregister_port(data->uart.port.line); + clk_disable_unprepare(data->clk); + + return 0; +} + +static const struct of_device_id bcm2835aux_serial_match[] = { + { .compatible = "brcm,bcm2835-aux-uart" }, + { }, +}; +MODULE_DEVICE_TABLE(of, bcm2835aux_serial_match); + +static struct platform_driver bcm2835aux_serial_driver = { + .driver = { + .name = "bcm2835-aux-uart", + .of_match_table = bcm2835aux_serial_match, + }, + .probe = bcm2835aux_serial_probe, + .remove = bcm2835aux_serial_remove, +}; +module_platform_driver(bcm2835aux_serial_driver); + +MODULE_DESCRIPTION("BCM2835 auxiliar UART driver"); +MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>"); +MODULE_LICENSE("GPL v2"); diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig index 6412f14..105aa19 100644 --- a/drivers/tty/serial/8250/Kconfig +++ b/drivers/tty/serial/8250/Kconfig @@ -272,6 +272,14 @@ config SERIAL_8250_ACORN system, say Y to this option. The driver can handle 1, 2, or 3 port cards. If unsure, say N. +config SERIAL_8250_BCM2835AUX + tristate "BCM2835 auxiliar uart support" + depends on ARCH_BCM2835 || COMPILE_TEST + depends on SERIAL_8250 && SERIAL_8250_SHARE_IRQ + help + support for the BCM2835 auxiliar uart. + If unsure, say N. + config SERIAL_8250_FSL bool depends on SERIAL_8250_CONSOLE diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile index e177f86..6327d0a 100644 --- a/drivers/tty/serial/8250/Makefile +++ b/drivers/tty/serial/8250/Makefile @@ -12,6 +12,7 @@ obj-$(CONFIG_SERIAL_8250_PCI) += 8250_pci.o obj-$(CONFIG_SERIAL_8250_HP300) += 8250_hp300.o obj-$(CONFIG_SERIAL_8250_CS) += serial_cs.o obj-$(CONFIG_SERIAL_8250_ACORN) += 8250_acorn.o +obj-$(CONFIG_SERIAL_8250_BCM2835AUX) += 8250_bcm2835aux.o obj-$(CONFIG_SERIAL_8250_CONSOLE) += 8250_early.o obj-$(CONFIG_SERIAL_8250_FOURPORT) += 8250_fourport.o obj-$(CONFIG_SERIAL_8250_ACCENT) += 8250_accent.o