[PATCH 1/2 v2] serial: mctrl_gpio: Check if GPIO property exisits before requesting it

[PATCH 1/2 v2] serial: mctrl_gpio: Check if GPIO property exisits before requesting it

[Stefan Roese]

This patch adds a check for the GPIOs property existence, before the
GPIO is requested. This fixes an issue seen when the 8250 mctrl_gpio
support is added (2nd patch in this patch series) on x86 platforms using
ACPI.

Here Mika's comments from 2016-08-09:

"
I noticed that with v4.8-rc1 serial console of some of our Broxton
systems does not work properly anymore. I'm able to see output but input
does not work.

I bisected it down to commit 4ef03d328769eddbfeca1f1c958fdb181a69c341
("tty/serial/8250: use mctrl_gpio helpers").

The reason why it fails is that in ACPI we do not have names for GPIOs
(except when _DSD is used) so we use the "idx" to index into _CRS GPIO
resources. Now mctrl_gpio_init_noauto() goes through a list of GPIOs
calling devm_gpiod_get_index_optional() passing "idx" of 0 for each. The
UART device in Broxton has following (simplified) ACPI description:

    Device (URT4)
    {
        ...
        Name (_CRS, ResourceTemplate () {
            GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
                    "\\_SB.GPO0", 0x00, ResourceConsumer)
            {
                0x003A
            }
            GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
                    "\\_SB.GPO0", 0x00, ResourceConsumer)
            {
                0x003D
            }
        })

In this case it finds the first GPIO (0x003A which happens to be RX pin
for that UART), turns it into GPIO which then breaks input for the UART
device. This also breaks systems with bluetooth connected to UART (those
typically have some GPIOs in their _CRS).

Any ideas how to fix this?

We cannot just drop the _CRS index lookup fallback because that would
break many existing machines out there so maybe we can limit this to
only DT enabled machines. Or alternatively probe if the property first
exists before trying to acquire the GPIOs (using
device_property_present()).
"

This patch implements the fix suggested by Mika in his statement above.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Yegor Yefremov <yegorslists@googlemail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Giulio Benetti <giulio.benetti@micronovasrl.com>
---
v2:
- Include the problem description and analysis from Mika into the commit
  text, as suggested by Greg.

 drivers/tty/serial/serial_mctrl_gpio.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
index 39ed56214cd3..cac50b20a119 100644
--- a/drivers/tty/serial/serial_mctrl_gpio.c
+++ b/drivers/tty/serial/serial_mctrl_gpio.c
@@ -116,6 +116,13 @@ struct mctrl_gpios *mctrl_gpio_init_noauto(struct device *dev, unsigned int idx)
 
 	for (i = 0; i < UART_GPIO_MAX; i++) {
 		enum gpiod_flags flags;
+		char *gpio_str;
+
+		/* Check if GPIO property exists and continue if not */
+		gpio_str = kasprintf(GFP_KERNEL, "%s-gpios",
+				     mctrl_gpios_desc[i].name);
+		if (!device_property_present(dev, gpio_str))
+			continue;
 
 		if (mctrl_gpios_desc[i].dir_out)
 			flags = GPIOD_OUT_LOW;
-- 
2.21.0

[PATCH 2/2 v2] tty/serial/8250: use mctrl_gpio helpers

[Stefan Roese]

From: Yegor Yefremov <yegorslists@googlemail.com>

This patch permits the usage for GPIOs to control
the CTS/RTS/DTR/DSR/DCD/RI signals.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Giulio Benetti <giulio.benetti@micronovasrl.com>
Cc: Yegor Yefremov <yegorslists@googlemail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
v2:
- No change

Please note that this patch was already applied before [1]. And later
reverted [2] because it introduced problems on some x86 based boards
(ACPI GPIO related). Here a detailed description of the issue at that
time:

https://lkml.org/lkml/2016/8/9/357
http://www.spinics.net/lists/linux-serial/msg23071.html

This is a re-send of the original patch that was applied at that time.
With patch 1/2 from this series this issue should be fixed now (please
note that I can't test it on such an x86 platform causing these
problems).

Andy (or Mika), perhaps it would be possible for you to test this
patch again, now with patch 1/2 of this series applied as well?
That would be really helpful.

Thanks,
Stefan

[1] 4ef03d328769 ("tty/serial/8250: use mctrl_gpio helpers")
[2] 5db4f7f80d16 ("Revert "tty/serial/8250: use mctrl_gpio helpers"")

 .../devicetree/bindings/serial/8250.txt       | 19 ++++++++++
 drivers/tty/serial/8250/8250.h                | 35 ++++++++++++++++++-
 drivers/tty/serial/8250/8250_core.c           |  9 +++++
 drivers/tty/serial/8250/8250_omap.c           | 31 +++++++++-------
 drivers/tty/serial/8250/8250_port.c           |  7 +++-
 drivers/tty/serial/8250/Kconfig               |  1 +
 include/linux/serial_8250.h                   |  1 +
 7 files changed, 88 insertions(+), 15 deletions(-)

diff --git a/Documentation/devicetree/bindings/serial/8250.txt b/Documentation/devicetree/bindings/serial/8250.txt
index 3cba12f855b7..20d351f268ef 100644
--- a/Documentation/devicetree/bindings/serial/8250.txt
+++ b/Documentation/devicetree/bindings/serial/8250.txt
@@ -53,6 +53,9 @@ Optional properties:
   programmable TX FIFO thresholds.
 - resets : phandle + reset specifier pairs
 - overrun-throttle-ms : how long to pause uart rx when input overrun is encountered.
+- {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:
@@ -74,3 +77,19 @@ 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>;
+		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 ebfb0bd5bef5..e59625bdb007 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -11,6 +11,8 @@
 #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);
@@ -141,12 +143,43 @@ void serial8250_em485_destroy(struct uart_8250_port *p);
 
 static inline void serial8250_out_MCR(struct uart_8250_port *up, int value)
 {
+	int mctrl_gpio = 0;
+
 	serial_out(up, UART_MCR, value);
+
+	if (value & UART_MCR_RTS)
+		mctrl_gpio |= TIOCM_RTS;
+	if (value & UART_MCR_DTR)
+		mctrl_gpio |= TIOCM_DTR;
+
+	mctrl_gpio_set(up->gpios, mctrl_gpio);
 }
 
 static inline int serial8250_in_MCR(struct uart_8250_port *up)
 {
-	return serial_in(up, UART_MCR);
+	int mctrl, mctrl_gpio = 0;
+
+	mctrl = serial_in(up, UART_MCR);
+
+	/* save current MCR values */
+	if (mctrl & UART_MCR_RTS)
+		mctrl_gpio |= TIOCM_RTS;
+	if (mctrl & UART_MCR_DTR)
+		mctrl_gpio |= TIOCM_DTR;
+
+	mctrl_gpio = mctrl_gpio_get_outputs(up->gpios, &mctrl_gpio);
+
+	if (mctrl_gpio & TIOCM_RTS)
+		mctrl |= UART_MCR_RTS;
+	else
+		mctrl &= ~UART_MCR_RTS;
+
+	if (mctrl_gpio & TIOCM_DTR)
+		mctrl |= UART_MCR_DTR;
+	else
+		mctrl &= ~UART_MCR_DTR;
+
+	return mctrl;
 }
 
 #if defined(__alpha__) && !defined(CONFIG_PCI)
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index e441221e04b9..ec0c5448c192 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -982,6 +982,8 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
 
 	uart = serial8250_find_match_or_unused(&up->port);
 	if (uart && uart->port.type != PORT_8250_CIR) {
+		struct mctrl_gpios *gpios;
+
 		if (uart->port.dev)
 			uart_remove_one_port(&serial8250_reg, &uart->port);
 
@@ -1016,6 +1018,13 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
 		if (up->port.flags & UPF_FIXED_TYPE)
 			uart->port.type = up->port.type;
 
+		gpios = mctrl_gpio_init(&uart->port, 0);
+		if (IS_ERR(gpios)) {
+			if (PTR_ERR(gpios) != -ENOSYS)
+				return PTR_ERR(gpios);
+		} else
+			uart->gpios = gpios;
+
 		serial8250_set_defaults(uart);
 
 		/* Possibly override default I/O functions.  */
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 0a8316632d75..562ac73d9f2f 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -141,18 +141,21 @@ static void omap8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
 
 	serial8250_do_set_mctrl(port, mctrl);
 
-	/*
-	 * Turn off autoRTS if RTS is lowered and restore autoRTS setting
-	 * if RTS is raised
-	 */
-	lcr = serial_in(up, UART_LCR);
-	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
-	if ((mctrl & TIOCM_RTS) && (port->status & UPSTAT_AUTORTS))
-		priv->efr |= UART_EFR_RTS;
-	else
-		priv->efr &= ~UART_EFR_RTS;
-	serial_out(up, UART_EFR, priv->efr);
-	serial_out(up, UART_LCR, lcr);
+	if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(up->gpios,
+						UART_GPIO_RTS))) {
+		/*
+		 * Turn off autoRTS if RTS is lowered and restore autoRTS
+		 * setting if RTS is raised
+		 */
+		lcr = serial_in(up, UART_LCR);
+		serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+		if ((mctrl & TIOCM_RTS) && (port->status & UPSTAT_AUTORTS))
+			priv->efr |= UART_EFR_RTS;
+		else
+			priv->efr &= ~UART_EFR_RTS;
+		serial_out(up, UART_EFR, priv->efr);
+		serial_out(up, UART_LCR, lcr);
+	}
 }
 
 /*
@@ -453,7 +456,9 @@ static void omap_8250_set_termios(struct uart_port *port,
 	priv->efr = 0;
 	up->port.status &= ~(UPSTAT_AUTOCTS | UPSTAT_AUTORTS | UPSTAT_AUTOXOFF);
 
-	if (termios->c_cflag & CRTSCTS && up->port.flags & UPF_HARD_FLOW) {
+	if (termios->c_cflag & CRTSCTS && up->port.flags & UPF_HARD_FLOW
+		&& IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(up->gpios,
+							UART_GPIO_RTS))) {
 		/* Enable AUTOCTS (autoRTS is enabled when RTS is raised) */
 		up->port.status |= UPSTAT_AUTOCTS | UPSTAT_AUTORTS;
 		priv->efr |= UART_EFR_CTS;
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 2304a84eee3b..220a78287d88 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1662,6 +1662,8 @@ 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);
 }
@@ -1674,6 +1676,8 @@ 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);
@@ -1959,7 +1963,8 @@ unsigned int serial8250_do_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);
 }
 EXPORT_SYMBOL_GPL(serial8250_do_get_mctrl);
 
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 296115f6a4d8..509f6a3bb9ff 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -8,6 +8,7 @@ config SERIAL_8250
 	tristate "8250/16550 and compatible serial support"
 	depends on !S390
 	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 5a655ba8d273..14cd763baf78 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -114,6 +114,7 @@ struct uart_8250_port {
 						 *   if no_console_suspend
 						 */
 	unsigned char		probe;
+	struct mctrl_gpios	*gpios;
 #define UART_PROBE_RSA	(1 << 0)
 
 	/*
-- 
2.21.0

Re: [PATCH 1/2 v2] serial: mctrl_gpio: Check if GPIO property exisits before requesting it

[Mika Westerberg]

On Fri, May 24, 2019 at 11:48:24AM +0200, Stefan Roese wrote:
> This patch adds a check for the GPIOs property existence, before the
> GPIO is requested. This fixes an issue seen when the 8250 mctrl_gpio
> support is added (2nd patch in this patch series) on x86 platforms using
> ACPI.
> 
> Here Mika's comments from 2016-08-09:
> 
> "
> I noticed that with v4.8-rc1 serial console of some of our Broxton
> systems does not work properly anymore. I'm able to see output but input
> does not work.
> 
> I bisected it down to commit 4ef03d328769eddbfeca1f1c958fdb181a69c341
> ("tty/serial/8250: use mctrl_gpio helpers").
> 
> The reason why it fails is that in ACPI we do not have names for GPIOs
> (except when _DSD is used) so we use the "idx" to index into _CRS GPIO
> resources. Now mctrl_gpio_init_noauto() goes through a list of GPIOs
> calling devm_gpiod_get_index_optional() passing "idx" of 0 for each. The
> UART device in Broxton has following (simplified) ACPI description:
> 
>     Device (URT4)
>     {
>         ...
>         Name (_CRS, ResourceTemplate () {
>             GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
>                     "\\_SB.GPO0", 0x00, ResourceConsumer)
>             {
>                 0x003A
>             }
>             GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
>                     "\\_SB.GPO0", 0x00, ResourceConsumer)
>             {
>                 0x003D
>             }
>         })
> 
> In this case it finds the first GPIO (0x003A which happens to be RX pin
> for that UART), turns it into GPIO which then breaks input for the UART
> device. This also breaks systems with bluetooth connected to UART (those
> typically have some GPIOs in their _CRS).
> 
> Any ideas how to fix this?
> 
> We cannot just drop the _CRS index lookup fallback because that would
> break many existing machines out there so maybe we can limit this to
> only DT enabled machines. Or alternatively probe if the property first
> exists before trying to acquire the GPIOs (using
> device_property_present()).
> "
> 
> This patch implements the fix suggested by Mika in his statement above.
> 
> Signed-off-by: Stefan Roese <sr@denx.de>
> Cc: Mika Westerberg <mika.westerberg@linux.intel.com>

Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Re: [PATCH 1/2 v2] serial: mctrl_gpio: Check if GPIO property exisits before requesting it

[Andy Shevchenko]

On Fri, May 24, 2019 at 1:21 PM Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
>
> On Fri, May 24, 2019 at 11:48:24AM +0200, Stefan Roese wrote:
> > This patch adds a check for the GPIOs property existence, before the
> > GPIO is requested. This fixes an issue seen when the 8250 mctrl_gpio
> > support is added (2nd patch in this patch series) on x86 platforms using
> > ACPI.
> >
> > Here Mika's comments from 2016-08-09:
> >
> > "
> > I noticed that with v4.8-rc1 serial console of some of our Broxton
> > systems does not work properly anymore. I'm able to see output but input
> > does not work.
> >
> > I bisected it down to commit 4ef03d328769eddbfeca1f1c958fdb181a69c341
> > ("tty/serial/8250: use mctrl_gpio helpers").
> >
> > The reason why it fails is that in ACPI we do not have names for GPIOs
> > (except when _DSD is used) so we use the "idx" to index into _CRS GPIO
> > resources. Now mctrl_gpio_init_noauto() goes through a list of GPIOs
> > calling devm_gpiod_get_index_optional() passing "idx" of 0 for each. The
> > UART device in Broxton has following (simplified) ACPI description:
> >
> >     Device (URT4)
> >     {
> >         ...
> >         Name (_CRS, ResourceTemplate () {
> >             GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
> >                     "\\_SB.GPO0", 0x00, ResourceConsumer)
> >             {
> >                 0x003A
> >             }
> >             GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
> >                     "\\_SB.GPO0", 0x00, ResourceConsumer)
> >             {
> >                 0x003D
> >             }
> >         })
> >
> > In this case it finds the first GPIO (0x003A which happens to be RX pin
> > for that UART), turns it into GPIO which then breaks input for the UART
> > device. This also breaks systems with bluetooth connected to UART (those
> > typically have some GPIOs in their _CRS).
> >
> > Any ideas how to fix this?
> >
> > We cannot just drop the _CRS index lookup fallback because that would
> > break many existing machines out there so maybe we can limit this to
> > only DT enabled machines. Or alternatively probe if the property first
> > exists before trying to acquire the GPIOs (using
> > device_property_present()).
> > "
> >
> > This patch implements the fix suggested by Mika in his statement above.
> >

We have a board where ASL provides _DSD for CTS and RxD pins.
I'm afraid this won't work on it.

Basically we need to understand the use of the GPIOs in UART. In our
case it's an out-of-band wake up source for UART.
Simply requiring GPIOs to be present is not enough.

Perhaps property like 'modem-control-gpio-in-use' (this seems a bad
name, given for sake of example).

> > Signed-off-by: Stefan Roese <sr@denx.de>
> > Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
>
> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>



-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/2 v2] serial: mctrl_gpio: Check if GPIO property exisits before requesting it

[Stefan Roese]

On 24.05.19 13:11, Andy Shevchenko wrote:
> On Fri, May 24, 2019 at 1:21 PM Mika Westerberg
> <mika.westerberg@linux.intel.com> wrote:
>>
>> On Fri, May 24, 2019 at 11:48:24AM +0200, Stefan Roese wrote:
>>> This patch adds a check for the GPIOs property existence, before the
>>> GPIO is requested. This fixes an issue seen when the 8250 mctrl_gpio
>>> support is added (2nd patch in this patch series) on x86 platforms using
>>> ACPI.
>>>
>>> Here Mika's comments from 2016-08-09:
>>>
>>> "
>>> I noticed that with v4.8-rc1 serial console of some of our Broxton
>>> systems does not work properly anymore. I'm able to see output but input
>>> does not work.
>>>
>>> I bisected it down to commit 4ef03d328769eddbfeca1f1c958fdb181a69c341
>>> ("tty/serial/8250: use mctrl_gpio helpers").
>>>
>>> The reason why it fails is that in ACPI we do not have names for GPIOs
>>> (except when _DSD is used) so we use the "idx" to index into _CRS GPIO
>>> resources. Now mctrl_gpio_init_noauto() goes through a list of GPIOs
>>> calling devm_gpiod_get_index_optional() passing "idx" of 0 for each. The
>>> UART device in Broxton has following (simplified) ACPI description:
>>>
>>>      Device (URT4)
>>>      {
>>>          ...
>>>          Name (_CRS, ResourceTemplate () {
>>>              GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
>>>                      "\\_SB.GPO0", 0x00, ResourceConsumer)
>>>              {
>>>                  0x003A
>>>              }
>>>              GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
>>>                      "\\_SB.GPO0", 0x00, ResourceConsumer)
>>>              {
>>>                  0x003D
>>>              }
>>>          })
>>>
>>> In this case it finds the first GPIO (0x003A which happens to be RX pin
>>> for that UART), turns it into GPIO which then breaks input for the UART
>>> device. This also breaks systems with bluetooth connected to UART (those
>>> typically have some GPIOs in their _CRS).
>>>
>>> Any ideas how to fix this?
>>>
>>> We cannot just drop the _CRS index lookup fallback because that would
>>> break many existing machines out there so maybe we can limit this to
>>> only DT enabled machines. Or alternatively probe if the property first
>>> exists before trying to acquire the GPIOs (using
>>> device_property_present()).
>>> "
>>>
>>> This patch implements the fix suggested by Mika in his statement above.
>>>
> 
> We have a board where ASL provides _DSD for CTS and RxD pins.
> I'm afraid this won't work on it.

With "won't work" you mean, that the GPIO can't be used for modem
control in this case in the current implementation (with this
patchset)? Or do you mean, that the breakage (input does not work
on Broxton systems) will not be solved by this patch?

If its the former, then I think that solving this issue is something
for a new patch, to support modem-control on such platforms as well
(if needed).

Please note that this patch is not trying to get modem-control working
on such ACPI based systems. Its targeted for device-tree enabled
platforms, using the 8250 serial driver, here specifically a MIPS
MT7688 based board. And just wants to fix the latter issue mentioned
above so that the 8250 modem-control support can be accepted in
mainline.
  
> Basically we need to understand the use of the GPIOs in UART. In our
> case it's an out-of-band wake up source for UART.
> Simply requiring GPIOs to be present is not enough.
> 
> Perhaps property like 'modem-control-gpio-in-use' (this seems a bad
> name, given for sake of example).

Thanks,
Stefan

Re: [PATCH 1/2 v2] serial: mctrl_gpio: Check if GPIO property exisits before requesting it

[Giulio Benetti]

Hello Stefan,

Il 24/05/2019 13:29, Stefan Roese ha scritto:
> On 24.05.19 13:11, Andy Shevchenko wrote:
>> On Fri, May 24, 2019 at 1:21 PM Mika Westerberg
>> <mika.westerberg@linux.intel.com> wrote:
>>>
>>> On Fri, May 24, 2019 at 11:48:24AM +0200, Stefan Roese wrote:
>>>> This patch adds a check for the GPIOs property existence, before the
>>>> GPIO is requested. This fixes an issue seen when the 8250 mctrl_gpio
>>>> support is added (2nd patch in this patch series) on x86 platforms using
>>>> ACPI.
>>>>
>>>> Here Mika's comments from 2016-08-09:
>>>>
>>>> "
>>>> I noticed that with v4.8-rc1 serial console of some of our Broxton
>>>> systems does not work properly anymore. I'm able to see output but input
>>>> does not work.
>>>>
>>>> I bisected it down to commit 4ef03d328769eddbfeca1f1c958fdb181a69c341
>>>> ("tty/serial/8250: use mctrl_gpio helpers").
>>>>
>>>> The reason why it fails is that in ACPI we do not have names for GPIOs
>>>> (except when _DSD is used) so we use the "idx" to index into _CRS GPIO
>>>> resources. Now mctrl_gpio_init_noauto() goes through a list of GPIOs
>>>> calling devm_gpiod_get_index_optional() passing "idx" of 0 for each. The
>>>> UART device in Broxton has following (simplified) ACPI description:
>>>>
>>>>       Device (URT4)
>>>>       {
>>>>           ...
>>>>           Name (_CRS, ResourceTemplate () {
>>>>               GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
>>>>                       "\\_SB.GPO0", 0x00, ResourceConsumer)
>>>>               {
>>>>                   0x003A
>>>>               }
>>>>               GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
>>>>                       "\\_SB.GPO0", 0x00, ResourceConsumer)
>>>>               {
>>>>                   0x003D
>>>>               }
>>>>           })
>>>>
>>>> In this case it finds the first GPIO (0x003A which happens to be RX pin
>>>> for that UART), turns it into GPIO which then breaks input for the UART
>>>> device. This also breaks systems with bluetooth connected to UART (those
>>>> typically have some GPIOs in their _CRS).
>>>>
>>>> Any ideas how to fix this?
>>>>
>>>> We cannot just drop the _CRS index lookup fallback because that would
>>>> break many existing machines out there so maybe we can limit this to
>>>> only DT enabled machines. Or alternatively probe if the property first
>>>> exists before trying to acquire the GPIOs (using
>>>> device_property_present()).
>>>> "
>>>>
>>>> This patch implements the fix suggested by Mika in his statement above.
>>>>
>>
>> We have a board where ASL provides _DSD for CTS and RxD pins.
>> I'm afraid this won't work on it.
> 
> With "won't work" you mean, that the GPIO can't be used for modem
> control in this case in the current implementation (with this
> patchset)? Or do you mean, that the breakage (input does not work
> on Broxton systems) will not be solved by this patch?
> 
> If its the former, then I think that solving this issue is something
> for a new patch, to support modem-control on such platforms as well
> (if needed).
> 
> Please note that this patch is not trying to get modem-control working
> on such ACPI based systems. Its targeted for device-tree enabled
> platforms, using the 8250 serial driver, here specifically a MIPS
> MT7688 based board. And just wants to fix the latter issue mentioned
> above so that the 8250 modem-control support can be accepted in
> mainline.

Take a look here:
https://lkml.org/lkml/2018/6/5/253

It's about waking up 8250 UART.
As I remember that is the problem.
I wanted to try to fix it but had no time.

What it broken as I remember is the capability to wake up linux on uart 
RX. Hope I've understood right at that time.

Best regards
-- 
Giulio Benetti
CTO

MICRONOVA SRL
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>> Basically we need to understand the use of the GPIOs in UART. In our
>> case it's an out-of-band wake up source for UART.
>> Simply requiring GPIOs to be present is not enough.
>>
>> Perhaps property like 'modem-control-gpio-in-use' (this seems a bad
>> name, given for sake of example).
> 
> Thanks,
> Stefan
> 

Re: [PATCH 1/2 v2] serial: mctrl_gpio: Check if GPIO property exisits before requesting it

[Andy Shevchenko]

On Fri, May 24, 2019 at 01:29:34PM +0200, Stefan Roese wrote:
> On 24.05.19 13:11, Andy Shevchenko wrote:
> > On Fri, May 24, 2019 at 1:21 PM Mika Westerberg
> > <mika.westerberg@linux.intel.com> wrote:
> > > 
> > > On Fri, May 24, 2019 at 11:48:24AM +0200, Stefan Roese wrote:
> > > > This patch adds a check for the GPIOs property existence, before the
> > > > GPIO is requested. This fixes an issue seen when the 8250 mctrl_gpio
> > > > support is added (2nd patch in this patch series) on x86 platforms using
> > > > ACPI.
> > > > 
> > > > Here Mika's comments from 2016-08-09:
> > > > 
> > > > "
> > > > I noticed that with v4.8-rc1 serial console of some of our Broxton
> > > > systems does not work properly anymore. I'm able to see output but input
> > > > does not work.
> > > > 
> > > > I bisected it down to commit 4ef03d328769eddbfeca1f1c958fdb181a69c341
> > > > ("tty/serial/8250: use mctrl_gpio helpers").
> > > > 
> > > > The reason why it fails is that in ACPI we do not have names for GPIOs
> > > > (except when _DSD is used) so we use the "idx" to index into _CRS GPIO
> > > > resources. Now mctrl_gpio_init_noauto() goes through a list of GPIOs
> > > > calling devm_gpiod_get_index_optional() passing "idx" of 0 for each. The
> > > > UART device in Broxton has following (simplified) ACPI description:
> > > > 
> > > >      Device (URT4)
> > > >      {
> > > >          ...
> > > >          Name (_CRS, ResourceTemplate () {
> > > >              GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
> > > >                      "\\_SB.GPO0", 0x00, ResourceConsumer)
> > > >              {
> > > >                  0x003A
> > > >              }
> > > >              GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
> > > >                      "\\_SB.GPO0", 0x00, ResourceConsumer)
> > > >              {
> > > >                  0x003D
> > > >              }
> > > >          })
> > > > 
> > > > In this case it finds the first GPIO (0x003A which happens to be RX pin
> > > > for that UART), turns it into GPIO which then breaks input for the UART
> > > > device. This also breaks systems with bluetooth connected to UART (those
> > > > typically have some GPIOs in their _CRS).
> > > > 
> > > > Any ideas how to fix this?
> > > > 
> > > > We cannot just drop the _CRS index lookup fallback because that would
> > > > break many existing machines out there so maybe we can limit this to
> > > > only DT enabled machines. Or alternatively probe if the property first
> > > > exists before trying to acquire the GPIOs (using
> > > > device_property_present()).
> > > > "
> > > > 
> > > > This patch implements the fix suggested by Mika in his statement above.
> > > > 
> > 
> > We have a board where ASL provides _DSD for CTS and RxD pins.
> > I'm afraid this won't work on it.
> 
> With "won't work" you mean, that the GPIO can't be used for modem
> control in this case in the current implementation (with this
> patchset)? Or do you mean, that the breakage (input does not work
> on Broxton systems) will not be solved by this patch?

It will solve RxD case, due to mctrl doesn't count RxD as a "control" line.

Though we have CTS pin defined for the same purpose, which means the hardware
flow control won't work on a subset of Broxton boards.

> If its the former, then I think that solving this issue is something
> for a new patch, to support modem-control on such platforms as well
> (if needed).

> Please note that this patch is not trying to get modem-control working
> on such ACPI based systems.

I understand that. At the same time it should not break existing systems.

> Its targeted for device-tree enabled
> platforms, using the 8250 serial driver, here specifically a MIPS
> MT7688 based board. And just wants to fix the latter issue mentioned
> above so that the 8250 modem-control support can be accepted in
> mainline.

As I said already we have to distinguish *the purpose* of these GPIOs.
(like CTS).

Can we apply this if and only if the device has no ACPI companion device?

In this case DT will work as you expect and ACPI won't be broken.

> > Basically we need to understand the use of the GPIOs in UART. In our
> > case it's an out-of-band wake up source for UART.
> > Simply requiring GPIOs to be present is not enough.
> > 
> > Perhaps property like 'modem-control-gpio-in-use' (this seems a bad
> > name, given for sake of example).

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/2 v2] serial: mctrl_gpio: Check if GPIO property exisits before requesting it

[Stefan Roese]

On 24.05.19 15:46, Andy Shevchenko wrote:
> On Fri, May 24, 2019 at 01:29:34PM +0200, Stefan Roese wrote:
>> On 24.05.19 13:11, Andy Shevchenko wrote:
>>> On Fri, May 24, 2019 at 1:21 PM Mika Westerberg
>>> <mika.westerberg@linux.intel.com> wrote:
>>>>
>>>> On Fri, May 24, 2019 at 11:48:24AM +0200, Stefan Roese wrote:
>>>>> This patch adds a check for the GPIOs property existence, before the
>>>>> GPIO is requested. This fixes an issue seen when the 8250 mctrl_gpio
>>>>> support is added (2nd patch in this patch series) on x86 platforms using
>>>>> ACPI.
>>>>>
>>>>> Here Mika's comments from 2016-08-09:
>>>>>
>>>>> "
>>>>> I noticed that with v4.8-rc1 serial console of some of our Broxton
>>>>> systems does not work properly anymore. I'm able to see output but input
>>>>> does not work.
>>>>>
>>>>> I bisected it down to commit 4ef03d328769eddbfeca1f1c958fdb181a69c341
>>>>> ("tty/serial/8250: use mctrl_gpio helpers").
>>>>>
>>>>> The reason why it fails is that in ACPI we do not have names for GPIOs
>>>>> (except when _DSD is used) so we use the "idx" to index into _CRS GPIO
>>>>> resources. Now mctrl_gpio_init_noauto() goes through a list of GPIOs
>>>>> calling devm_gpiod_get_index_optional() passing "idx" of 0 for each. The
>>>>> UART device in Broxton has following (simplified) ACPI description:
>>>>>
>>>>>       Device (URT4)
>>>>>       {
>>>>>           ...
>>>>>           Name (_CRS, ResourceTemplate () {
>>>>>               GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
>>>>>                       "\\_SB.GPO0", 0x00, ResourceConsumer)
>>>>>               {
>>>>>                   0x003A
>>>>>               }
>>>>>               GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
>>>>>                       "\\_SB.GPO0", 0x00, ResourceConsumer)
>>>>>               {
>>>>>                   0x003D
>>>>>               }
>>>>>           })
>>>>>
>>>>> In this case it finds the first GPIO (0x003A which happens to be RX pin
>>>>> for that UART), turns it into GPIO which then breaks input for the UART
>>>>> device. This also breaks systems with bluetooth connected to UART (those
>>>>> typically have some GPIOs in their _CRS).
>>>>>
>>>>> Any ideas how to fix this?
>>>>>
>>>>> We cannot just drop the _CRS index lookup fallback because that would
>>>>> break many existing machines out there so maybe we can limit this to
>>>>> only DT enabled machines. Or alternatively probe if the property first
>>>>> exists before trying to acquire the GPIOs (using
>>>>> device_property_present()).
>>>>> "
>>>>>
>>>>> This patch implements the fix suggested by Mika in his statement above.
>>>>>
>>>
>>> We have a board where ASL provides _DSD for CTS and RxD pins.
>>> I'm afraid this won't work on it.
>>
>> With "won't work" you mean, that the GPIO can't be used for modem
>> control in this case in the current implementation (with this
>> patchset)? Or do you mean, that the breakage (input does not work
>> on Broxton systems) will not be solved by this patch?
> 
> It will solve RxD case, due to mctrl doesn't count RxD as a "control" line.
> 
> Though we have CTS pin defined for the same purpose, which means the hardware
> flow control won't work on a subset of Broxton boards.
> 
>> If its the former, then I think that solving this issue is something
>> for a new patch, to support modem-control on such platforms as well
>> (if needed).
> 
>> Please note that this patch is not trying to get modem-control working
>> on such ACPI based systems.
> 
> I understand that. At the same time it should not break existing systems.
> 
>> Its targeted for device-tree enabled
>> platforms, using the 8250 serial driver, here specifically a MIPS
>> MT7688 based board. And just wants to fix the latter issue mentioned
>> above so that the 8250 modem-control support can be accepted in
>> mainline.
> 
> As I said already we have to distinguish *the purpose* of these GPIOs.
> (like CTS).
> 
> Can we apply this if and only if the device has no ACPI companion device?
> 
> In this case DT will work as you expect and ACPI won't be broken.

So your suggestion is to add a has_acpi_companion() check before
mctrl_gpio_init() is called in serial8250_register_8250_port() and
then only use the gpio related mctrl, if the GPIO's are really used?

I can certainly change patch 2/2 to do this. It would be great though,
if you (or someone else) could test this on such a ACPI based platform,
as I don't have access to such a board.

Thanks,
Stefan