On 03/10/2016 08:36 AM, Peter Hurley wrote:
> Hi Yegor,
>
> On 03/09/2016 03:03 AM, yegorslists@xxxxxxxxxxxxxx wrote:
>> From: Yegor Yefremov <yegorslists@xxxxxxxxxxxxxx>
>>
>> This patch permits the usage fo GPIOs to control the CTS/RTS/DTR/DSR/DCD/RI
>> signals.
>
> Comments below.
>
>
>> Signed-off-by: Yegor Yefremov <yegorslists@xxxxxxxxxxxxxx>
>> ---
>> Documentation/devicetree/bindings/serial/8250.txt | 21 +++++++++++++++++++++
>> drivers/tty/serial/8250/8250.h | 2 ++
>> drivers/tty/serial/8250/8250_core.c | 5 +++++
>> drivers/tty/serial/8250/8250_port.c | 11 ++++++++++-
>> drivers/tty/serial/8250/Kconfig | 1 +
>> include/linux/serial_8250.h | 1 +
>> 6 files changed, 40 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/serial/8250.txt b/Documentation/devicetree/bindings/serial/8250.txt
>> index 936ab5b..277e0ee 100644
>> --- a/Documentation/devicetree/bindings/serial/8250.txt
>> +++ b/Documentation/devicetree/bindings/serial/8250.txt
>> @@ -42,6 +42,9 @@ Optional properties:
>> - auto-flow-control: one way to enable automatic flow control support. The
>> driver is allowed to detect support for the capability even without this
>> property.
>> +- {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD
>> + line respectively. It will use specified GPIO instead of the peripheral
>> + function pin for the UART feature. If unsure, don't specify this property.
>>
>> Note:
>> * fsl,ns16550:
>> @@ -63,3 +66,21 @@ Example:
>> interrupts = <10>;
>> reg-shift = <2>;
>> };
>> +
>> +Example for OMAP UART using GPIO-based modem control signals:
>> +
>> + uart4: serial@49042000 {
>> + compatible = "ti,omap3-uart";
>> + reg = <0x49042000 0x400>;
>> + interrupts = <80>;
>
>> + dmas = <&sdma 81 &sdma 82>;
>> + dma-names = "tx", "rx";
>
> Drop the DMA example; omap3 sdma is broken wrt to uart.
>
>
>> + ti,hwmods = "uart4";
>> + clock-frequency = <48000000>;
>> + cts-gpios = <&gpio3 5 GPIO_ACTIVE_LOW>;
>> + rts-gpios = <&gpio3 6 GPIO_ACTIVE_LOW>;
>> + dtr-gpios = <&gpio1 12 GPIO_ACTIVE_LOW>;
>> + dsr-gpios = <&gpio1 13 GPIO_ACTIVE_LOW>;
>> + dcd-gpios = <&gpio1 14 GPIO_ACTIVE_LOW>;
>> + rng-gpios = <&gpio1 15 GPIO_ACTIVE_LOW>;
>> + };
>> diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
>> index d54dcd8..98ee73c 100644
>> --- a/drivers/tty/serial/8250/8250.h
>> +++ b/drivers/tty/serial/8250/8250.h
>> @@ -15,6 +15,8 @@
>> #include <linux/serial_reg.h>
>> #include <linux/dmaengine.h>
>>
>> +#include "../serial_mctrl_gpio.h"
>> +
>> struct uart_8250_dma {
>> int (*tx_dma)(struct uart_8250_port *p);
>> int (*rx_dma)(struct uart_8250_port *p, unsigned int iir);
>> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
>> index c9720a9..cadcaa5 100644
>> --- a/drivers/tty/serial/8250/8250_core.c
>> +++ b/drivers/tty/serial/8250/8250_core.c
>> @@ -1004,6 +1004,10 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>> if (up->port.flags & UPF_FIXED_TYPE)
>> uart->port.type = up->port.type;
>>
>> + uart->gpios = mctrl_gpio_init(&uart->port, 0);
>> + if (IS_ERR(uart->gpios))
>> + return PTR_ERR(uart->gpios);
Also, autoRTS needs to be disabled if RTS is a gpio.
Similarly for autoCTS.
>> +
>> serial8250_set_defaults(uart);
>>
>> /* Possibly override default I/O functions. */
>> @@ -1049,6 +1053,7 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>>
>> ret = 0;
>> }
>> +
>> }
>> mutex_unlock(&serial_mutex);
>>
>> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
>> index 8d262bc..e7bfeef 100644
>> --- a/drivers/tty/serial/8250/8250_port.c
>> +++ b/drivers/tty/serial/8250/8250_port.c
>> @@ -1393,6 +1393,8 @@ static void serial8250_disable_ms(struct uart_port *port)
>> if (up->bugs & UART_BUG_NOMSR)
>> return;
>>
>> + mctrl_gpio_disable_ms(up->gpios);
>> +
>> up->ier &= ~UART_IER_MSI;
>> serial_port_out(port, UART_IER, up->ier);
>> }
>> @@ -1405,6 +1407,8 @@ static void serial8250_enable_ms(struct uart_port *port)
>> if (up->bugs & UART_BUG_NOMSR)
>> return;
>>
>> + mctrl_gpio_enable_ms(up->gpios);
>> +
>> up->ier |= UART_IER_MSI;
>>
>> serial8250_rpm_get(up);
>> @@ -1680,7 +1684,8 @@ static unsigned int serial8250_get_mctrl(struct uart_port *port)
>> ret |= TIOCM_DSR;
>> if (status & UART_MSR_CTS)
>> ret |= TIOCM_CTS;
>> - return ret;
>> +
>> + return mctrl_gpio_get(up->gpios, &ret);
>
> This is ugly; why is mctrl pass-by-reference when it's returned anyway?
>
> return mctrl_gpio_get(up->gpio, ret);
>
>
>> }
>>
>> void serial8250_do_set_mctrl(struct uart_port *port, unsigned int mctrl)
>> @@ -1707,10 +1712,14 @@ EXPORT_SYMBOL_GPL(serial8250_do_set_mctrl);
>>
>> static void serial8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
>> {
>> + struct uart_8250_port *up = up_to_u8250p(port);
>> +
>> if (port->set_mctrl)
>> port->set_mctrl(port, mctrl);
>> else
>> serial8250_do_set_mctrl(port, mctrl);
>> +
>> + mctrl_gpio_set(up->gpios, mctrl);
>
> The 8250 driver virtualizes RTS because some h/w does not
> support RTS override with autoRTS on.
>
> So this won't work properly.
> And this won't work for RS485.
>
> Rather, transform
>
> serial_out(port, UART_MCR, val);
> serial_port_out(up, UART_MCR, val);
>
> to
>
> serial8250_out_MCR(up, val);
>
> and add the gpio setting to that.
> Do the transform first in a prequel patch; then add gpio to that.
>
> Similarly for serial_in(port, UART_MCR)
>
> Regards,
> Peter Hurley
>
>
>> }
>>
>> static void serial8250_break_ctl(struct uart_port *port, int break_state)
>> diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
>> index b03cb517..997e9a8 100644
>> --- a/drivers/tty/serial/8250/Kconfig
>> +++ b/drivers/tty/serial/8250/Kconfig
>> @@ -6,6 +6,7 @@
>> config SERIAL_8250
>> tristate "8250/16550 and compatible serial support"
>> select SERIAL_CORE
>> + select SERIAL_MCTRL_GPIO if GPIOLIB
>> ---help---
>> This selects whether you want to include the driver for the standard
>> serial ports. The standard answer is Y. People who might say N
>> diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
>> index faa0e03..86a3ef4 100644
>> --- a/include/linux/serial_8250.h
>> +++ b/include/linux/serial_8250.h
>> @@ -104,6 +104,7 @@ struct uart_8250_port {
>> * if no_console_suspend
>> */
>> unsigned char probe;
>> + struct mctrl_gpios *gpios;
>> #define UART_PROBE_RSA (1 << 0)
>>
>> /*
>>
>
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