From: Stefan Wahren <stefan.wahren-eS4NqCHxEME@public.gmane.org> To: kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org Cc: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>, Lee Jones <lee-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Eric Anholt <eric-WhKQ6XTQaPysTnJN9+BGXg@public.gmane.org>, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>, Jiri Slaby <jslaby-IBi9RG/b67k@public.gmane.org>, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-rpi-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Subject: Re: [PATCH V2 2/2] serial: bcm2835: add driver for bcm2835-aux-uart Date: Mon, 11 Jan 2016 10:52:32 +0100 [thread overview] Message-ID: <56937B60.5020200@i2se.com> (raw) In-Reply-To: <1452344854-2576-3-git-send-email-kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org> Hi Martin, Am 09.01.2016 um 14:07 schrieb kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org: > From: Martin Sperl <kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.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-TqfNSX0MhmxHKSADF0wUEw@public.gmane.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-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org> > + * > + * Based on 8250_lpc18xx.c: > + * Copyright (C) 2015 Joachim Eastwood <manabian-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> > + * > + * 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-TqfNSX0MhmxHKSADF0wUEw@public.gmane.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 > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html
WARNING: multiple messages have this Message-ID (diff)
From: stefan.wahren@i2se.com (Stefan Wahren) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH V2 2/2] serial: bcm2835: add driver for bcm2835-aux-uart Date: Mon, 11 Jan 2016 10:52:32 +0100 [thread overview] Message-ID: <56937B60.5020200@i2se.com> (raw) In-Reply-To: <1452344854-2576-3-git-send-email-kernel@martin.sperl.org> Hi Martin, Am 09.01.2016 um 14:07 schrieb kernel at 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 >
next prev parent reply other threads:[~2016-01-11 9:52 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-01-09 13:07 [PATCH V2 0/2] serial: bcm2835: add bcm2835 auxiliar uart driver kernel-TqfNSX0MhmxHKSADF0wUEw 2016-01-09 13:07 ` kernel at martin.sperl.org [not found] ` <1452344854-2576-1-git-send-email-kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org> 2016-01-09 13:07 ` [PATCH V2 1/2] dt/bindings: serial: bcm2835: add binding documentation for bcm2835-aux-uart kernel-TqfNSX0MhmxHKSADF0wUEw 2016-01-09 13:07 ` kernel at martin.sperl.org [not found] ` <1452344854-2576-2-git-send-email-kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org> 2016-01-09 20:53 ` Arnd Bergmann 2016-01-09 20:53 ` Arnd Bergmann 2016-01-10 10:49 ` Martin Sperl 2016-01-10 10:49 ` Martin Sperl [not found] ` <175E89CE-581C-48AB-B7FF-6E9A41B033D5-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org> 2016-01-11 12:21 ` Arnd Bergmann 2016-01-11 12:21 ` Arnd Bergmann 2016-01-11 13:57 ` Martin Sperl 2016-01-11 13:57 ` Martin Sperl [not found] ` <6035A0DD-AD61-48F7-B641-272BB23F3CD8-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org> 2016-01-11 14:40 ` Arnd Bergmann 2016-01-11 14:40 ` Arnd Bergmann 2016-01-28 6:39 ` Eric Anholt 2016-01-28 6:39 ` Eric Anholt 2016-01-09 13:07 ` [PATCH V2 2/2] serial: bcm2835: add driver " kernel-TqfNSX0MhmxHKSADF0wUEw 2016-01-09 13:07 ` kernel at martin.sperl.org [not found] ` <1452344854-2576-3-git-send-email-kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org> 2016-01-11 9:52 ` Stefan Wahren [this message] 2016-01-11 9:52 ` Stefan Wahren 2016-01-11 15:25 ` Peter Korsgaard 2016-01-11 15:25 ` Peter Korsgaard 2016-01-10 15:05 ` [PATCH V2 0/2] serial: bcm2835: add bcm2835 auxiliar uart driver Stefan Wahren 2016-01-10 15:05 ` Stefan Wahren [not found] ` <1057226922.507844.cb24b396-67be-4b7b-9938-7cb30ef4fe05.open-xchange-7tX72C7vayboQLBSYMtkGA@public.gmane.org> 2016-01-10 15:45 ` Martin Sperl 2016-01-10 15:45 ` Martin Sperl [not found] ` <46FD7886-510C-4F0F-A039-500D5438207B-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org> 2016-01-10 21:17 ` Stefan Wahren 2016-01-10 21:17 ` Stefan Wahren
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