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 <[email protected]>
Reviewed-by: Mika Westerberg <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Cc: Mika Westerberg <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Yegor Yefremov <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Giulio Benetti <[email protected]>
---
v7:
- Include <linux/property.h> to fix compile breakage on OMAP
v6:
- No change
v5:
- Simplified the code a bit (Andy)
- Added gpio_str == NULL handling (Andy)
v4:
- Add missing free() calls (Johan)
- Added Mika's reviewed by tag
- Added Johan to Cc
v3:
- No change
v2:
- Include the problem description and analysis from Mika into the commit
text, as suggested by Greg.
drivers/tty/serial/serial_mctrl_gpio.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
index 39ed56214cd3..2b400189be91 100644
--- a/drivers/tty/serial/serial_mctrl_gpio.c
+++ b/drivers/tty/serial/serial_mctrl_gpio.c
@@ -12,6 +12,7 @@
#include <linux/termios.h>
#include <linux/serial_core.h>
#include <linux/module.h>
+#include <linux/property.h>
#include "serial_mctrl_gpio.h"
@@ -116,6 +117,19 @@ 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;
+ bool present;
+
+ /* Check if GPIO property exists and continue if not */
+ gpio_str = kasprintf(GFP_KERNEL, "%s-gpios",
+ mctrl_gpios_desc[i].name);
+ if (!gpio_str)
+ continue;
+
+ present = device_property_present(dev, gpio_str);
+ kfree(gpio_str);
+ if (!present)
+ continue;
if (mctrl_gpios_desc[i].dir_out)
flags = GPIOD_OUT_LOW;
--
2.22.0
From: Yegor Yefremov <[email protected]>
This patch permits the usage for GPIOs to control
the CTS/RTS/DTR/DSR/DCD/RI signals.
Changed by Stefan:
Only call mctrl_gpio_init(), if the device has no ACPI companion device
to not break existing ACPI based systems. Also only use the mctrl_gpio_
functions when "gpios" is available.
Use MSR / MCR <-> TIOCM wrapper functions.
Signed-off-by: Yegor Yefremov <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Stefan Roese <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Reviewed-by: Mika Westerberg <[email protected]>
Cc: Mika Westerberg <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Giulio Benetti <[email protected]>
Cc: Yegor Yefremov <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
---
v7:
- Change serial8250_do_get_mctrl() so that systems with a "mixed setup"
(i.e. CTS controlled by UART but other status pins controlled by GPIO)
are also supported again (Yegor)
v6:
- Use newly introduced TIOCM <-> MCR/MSR wrapper functions
- serial8250_in_MCR(): Don't save the already read MCR bits in TIOCM
format but "or" them later to the GPIO MCR value
- Correctly use "!up->gpios" (Andy)
- Removed Mika's reviewed by tag (because of changes)
v5:
- Dropped a few "if (up->gpios)" checks, as the mctrl_gpio_foo() API
handles gpios == NULL (return)
- 8250_omap: Changed "IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(up->gpios, ...))"
to "up->gpios == NULL", as mctrl_gpio_to_gpiod() does not handle
gpios == NULL correctly.
v4:
- Added Mika's reviewed by tag
- Added Johan to Cc
v3:
- Only call mctrl_gpio_init(), if the device has no ACPI companion device
to not break existing ACPI based systems, as suggested by Andy
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 | 18 +++++++++++-
drivers/tty/serial/8250/8250_core.c | 17 +++++++++++
drivers/tty/serial/8250/8250_omap.c | 29 ++++++++++---------
drivers/tty/serial/8250/8250_port.c | 11 ++++++-
drivers/tty/serial/8250/Kconfig | 1 +
include/linux/serial_8250.h | 1 +
7 files changed, 81 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 793da2e510e0..75c7c5449461 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);
@@ -196,11 +198,25 @@ static inline int serial8250_MSR_to_TIOCM(int msr)
static inline void serial8250_out_MCR(struct uart_8250_port *up, int value)
{
serial_out(up, UART_MCR, value);
+
+ if (up->gpios)
+ mctrl_gpio_set(up->gpios, serial8250_MCR_to_TIOCM(value));
}
static inline int serial8250_in_MCR(struct uart_8250_port *up)
{
- return serial_in(up, UART_MCR);
+ int mctrl;
+
+ mctrl = serial_in(up, UART_MCR);
+
+ if (up->gpios) {
+ unsigned int mctrl_gpio = 0;
+
+ mctrl_gpio = mctrl_gpio_get_outputs(up->gpios, &mctrl_gpio);
+ mctrl |= serial8250_TIOCM_to_MCR(mctrl_gpio);
+ }
+
+ 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..a4470771005f 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -14,6 +14,7 @@
* serial8250_register_8250_port() ports
*/
+#include <linux/acpi.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ioport.h>
@@ -982,6 +983,8 @@ 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 +1019,20 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
if (up->port.flags & UPF_FIXED_TYPE)
uart->port.type = up->port.type;
+ /*
+ * Only call mctrl_gpio_init(), if the device has no ACPI
+ * companion device
+ */
+ if (!has_acpi_companion(uart->port.dev)) {
+ 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..d5bbfc8f2284 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -141,18 +141,20 @@ 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 (!up->gpios) {
+ /*
+ * 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 +455,8 @@ 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 &&
+ !up->gpios) {
/* 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 47f0a8d01a57..ff3dd0c1c90a 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);
@@ -1944,12 +1948,17 @@ unsigned int serial8250_do_get_mctrl(struct uart_port *port)
{
struct uart_8250_port *up = up_to_u8250p(port);
unsigned int status;
+ unsigned int val;
serial8250_rpm_get(up);
status = serial8250_modem_status(up);
serial8250_rpm_put(up);
- return serial8250_MSR_to_TIOCM(status);
+ val = serial8250_MSR_to_TIOCM(status);
+ if (up->gpios)
+ return mctrl_gpio_get(up->gpios, &val);
+
+ return val;
}
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 5e0b59422a68..bb2bc99388ca 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -110,6 +110,7 @@ struct uart_8250_port {
* if no_console_suspend
*/
unsigned char probe;
+ struct mctrl_gpios *gpios;
#define UART_PROBE_RSA (1 << 0)
/*
--
2.22.0
On Mon, Jun 17, 2019 at 5:00 PM Stefan Roese <[email protected]> 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 <[email protected]>
> Reviewed-by: Mika Westerberg <[email protected]>
> Reviewed-by: Andy Shevchenko <[email protected]>
> Cc: Mika Westerberg <[email protected]>
> Cc: Andy Shevchenko <[email protected]>
> Cc: Yegor Yefremov <[email protected]>
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: Giulio Benetti <[email protected]>
Tested-by: Yegor Yefremov <[email protected]>
> ---
> v7:
> - Include <linux/property.h> to fix compile breakage on OMAP
>
> v6:
> - No change
>
> v5:
> - Simplified the code a bit (Andy)
> - Added gpio_str == NULL handling (Andy)
>
> v4:
> - Add missing free() calls (Johan)
> - Added Mika's reviewed by tag
> - Added Johan to Cc
>
> v3:
> - No change
>
> v2:
> - Include the problem description and analysis from Mika into the commit
> text, as suggested by Greg.
>
> drivers/tty/serial/serial_mctrl_gpio.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
> index 39ed56214cd3..2b400189be91 100644
> --- a/drivers/tty/serial/serial_mctrl_gpio.c
> +++ b/drivers/tty/serial/serial_mctrl_gpio.c
> @@ -12,6 +12,7 @@
> #include <linux/termios.h>
> #include <linux/serial_core.h>
> #include <linux/module.h>
> +#include <linux/property.h>
>
> #include "serial_mctrl_gpio.h"
>
> @@ -116,6 +117,19 @@ 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;
> + bool present;
> +
> + /* Check if GPIO property exists and continue if not */
> + gpio_str = kasprintf(GFP_KERNEL, "%s-gpios",
> + mctrl_gpios_desc[i].name);
> + if (!gpio_str)
> + continue;
> +
> + present = device_property_present(dev, gpio_str);
> + kfree(gpio_str);
> + if (!present)
> + continue;
>
> if (mctrl_gpios_desc[i].dir_out)
> flags = GPIOD_OUT_LOW;
> --
> 2.22.0
>
On Mon, Jun 17, 2019 at 5:00 PM Stefan Roese <[email protected]> wrote:
>
> From: Yegor Yefremov <[email protected]>
>
> This patch permits the usage for GPIOs to control
> the CTS/RTS/DTR/DSR/DCD/RI signals.
>
> Changed by Stefan:
> Only call mctrl_gpio_init(), if the device has no ACPI companion device
> to not break existing ACPI based systems. Also only use the mctrl_gpio_
> functions when "gpios" is available.
>
> Use MSR / MCR <-> TIOCM wrapper functions.
>
> Signed-off-by: Yegor Yefremov <[email protected]>
> Signed-off-by: Greg Kroah-Hartman <[email protected]>
> Signed-off-by: Stefan Roese <[email protected]>
> Reviewed-by: Andy Shevchenko <[email protected]>
> Reviewed-by: Mika Westerberg <[email protected]>
> Cc: Mika Westerberg <[email protected]>
> Cc: Andy Shevchenko <[email protected]>
> Cc: Giulio Benetti <[email protected]>
> Cc: Yegor Yefremov <[email protected]>
> Cc: Greg Kroah-Hartman <[email protected]>
Tested-by: Yegor Yefremov <[email protected]>
Thanks for reviving my initial patch series and bringing them into shape.
Yegor
> ---
> v7:
> - Change serial8250_do_get_mctrl() so that systems with a "mixed setup"
> (i.e. CTS controlled by UART but other status pins controlled by GPIO)
> are also supported again (Yegor)
>
> v6:
> - Use newly introduced TIOCM <-> MCR/MSR wrapper functions
> - serial8250_in_MCR(): Don't save the already read MCR bits in TIOCM
> format but "or" them later to the GPIO MCR value
> - Correctly use "!up->gpios" (Andy)
> - Removed Mika's reviewed by tag (because of changes)
>
> v5:
> - Dropped a few "if (up->gpios)" checks, as the mctrl_gpio_foo() API
> handles gpios == NULL (return)
> - 8250_omap: Changed "IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(up->gpios, ...))"
> to "up->gpios == NULL", as mctrl_gpio_to_gpiod() does not handle
> gpios == NULL correctly.
>
> v4:
> - Added Mika's reviewed by tag
> - Added Johan to Cc
>
> v3:
> - Only call mctrl_gpio_init(), if the device has no ACPI companion device
> to not break existing ACPI based systems, as suggested by Andy
>
> 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 | 18 +++++++++++-
> drivers/tty/serial/8250/8250_core.c | 17 +++++++++++
> drivers/tty/serial/8250/8250_omap.c | 29 ++++++++++---------
> drivers/tty/serial/8250/8250_port.c | 11 ++++++-
> drivers/tty/serial/8250/Kconfig | 1 +
> include/linux/serial_8250.h | 1 +
> 7 files changed, 81 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 793da2e510e0..75c7c5449461 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);
> @@ -196,11 +198,25 @@ static inline int serial8250_MSR_to_TIOCM(int msr)
> static inline void serial8250_out_MCR(struct uart_8250_port *up, int value)
> {
> serial_out(up, UART_MCR, value);
> +
> + if (up->gpios)
> + mctrl_gpio_set(up->gpios, serial8250_MCR_to_TIOCM(value));
> }
>
> static inline int serial8250_in_MCR(struct uart_8250_port *up)
> {
> - return serial_in(up, UART_MCR);
> + int mctrl;
> +
> + mctrl = serial_in(up, UART_MCR);
> +
> + if (up->gpios) {
> + unsigned int mctrl_gpio = 0;
> +
> + mctrl_gpio = mctrl_gpio_get_outputs(up->gpios, &mctrl_gpio);
> + mctrl |= serial8250_TIOCM_to_MCR(mctrl_gpio);
> + }
> +
> + 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..a4470771005f 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -14,6 +14,7 @@
> * serial8250_register_8250_port() ports
> */
>
> +#include <linux/acpi.h>
> #include <linux/module.h>
> #include <linux/moduleparam.h>
> #include <linux/ioport.h>
> @@ -982,6 +983,8 @@ 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 +1019,20 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
> if (up->port.flags & UPF_FIXED_TYPE)
> uart->port.type = up->port.type;
>
> + /*
> + * Only call mctrl_gpio_init(), if the device has no ACPI
> + * companion device
> + */
> + if (!has_acpi_companion(uart->port.dev)) {
> + 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..d5bbfc8f2284 100644
> --- a/drivers/tty/serial/8250/8250_omap.c
> +++ b/drivers/tty/serial/8250/8250_omap.c
> @@ -141,18 +141,20 @@ 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 (!up->gpios) {
> + /*
> + * 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 +455,8 @@ 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 &&
> + !up->gpios) {
> /* 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 47f0a8d01a57..ff3dd0c1c90a 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);
> @@ -1944,12 +1948,17 @@ unsigned int serial8250_do_get_mctrl(struct uart_port *port)
> {
> struct uart_8250_port *up = up_to_u8250p(port);
> unsigned int status;
> + unsigned int val;
>
> serial8250_rpm_get(up);
> status = serial8250_modem_status(up);
> serial8250_rpm_put(up);
>
> - return serial8250_MSR_to_TIOCM(status);
> + val = serial8250_MSR_to_TIOCM(status);
> + if (up->gpios)
> + return mctrl_gpio_get(up->gpios, &val);
> +
> + return val;
> }
> 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 5e0b59422a68..bb2bc99388ca 100644
> --- a/include/linux/serial_8250.h
> +++ b/include/linux/serial_8250.h
> @@ -110,6 +110,7 @@ struct uart_8250_port {
> * if no_console_suspend
> */
> unsigned char probe;
> + struct mctrl_gpios *gpios;
> #define UART_PROBE_RSA (1 << 0)
>
> /*
> --
> 2.22.0
>