drivers/tty/serial/8250: Make Aspeed VUART SIRQ polarity configurable

Make the SIRQ polarity for Aspeed AST24xx/25xx VUART configurable via
sysfs. This setting need to be changed on specific host platforms
depending on the selected host interface (LPC / eSPI).

The setting is configurable via sysfs rather than device-tree to stay in
line with other related configurable settings.

On AST2500 the VUART SIRQ polarity can be auto-configured by reading a
bit from a configuration register, e.g. the LPC/eSPI interface
configuration bit.

Tested: Verified on TYAN S7106 mainboard.
Signed-off-by: Oskar Senft <osk@google.com>
Link: https://lore.kernel.org/r/20190905144130.220713-1-osk@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/ABI/stable/sysfs-driver-aspeed-vuart b/Documentation/ABI/stable/sysfs-driver-aspeed-vuart
index 8062953..950cafc 100644 (file)
--- a/Documentation/ABI/stable/sysfs-driver-aspeed-vuart
+++ b/Documentation/ABI/stable/sysfs-driver-aspeed-vuart
@@ -6,10 +6,19 @@ Description:  Configures which IO port the host side of the UART
 Users:         OpenBMC.  Proposed changes should be mailed to
                openbmc@lists.ozlabs.org
 
-What:          /sys/bus/platform/drivers/aspeed-vuart*/sirq
+What:          /sys/bus/platform/drivers/aspeed-vuart/*/sirq
 Date:          April 2017
 Contact:       Jeremy Kerr <jk@ozlabs.org>
 Description:   Configures which interrupt number the host side of
                the UART will appear on the host <-> BMC LPC bus.
 Users:         OpenBMC.  Proposed changes should be mailed to
                openbmc@lists.ozlabs.org
+
+What:          /sys/bus/platform/drivers/aspeed-vuart/*/sirq_polarity
+Date:          July 2019
+Contact:       Oskar Senft <osk@google.com>
+Description:   Configures the polarity of the serial interrupt to the
+               host via the BMC LPC bus.
+               Set to 0 for active-low or 1 for active-high.
+Users:         OpenBMC.  Proposed changes should be mailed to
+               openbmc@lists.ozlabs.org

diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c
index 0438d9a..6e67fd8 100644 (file)
--- a/drivers/tty/serial/8250/8250_aspeed_vuart.c
+++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c
@@ -14,6 +14,8 @@
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
+#include <linux/regmap.h>
+#include <linux/mfd/syscon.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
 #include <linux/clk.h>
@@ -22,6 +24,7 @@
 
 #define ASPEED_VUART_GCRA              0x20
 #define ASPEED_VUART_GCRA_VUART_EN             BIT(0)
+#define ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY   BIT(1)
 #define ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD BIT(5)
 #define ASPEED_VUART_GCRB              0x24
 #define ASPEED_VUART_GCRB_HOST_SIRQ_MASK       GENMASK(7, 4)
@@ -131,8 +134,53 @@ static ssize_t sirq_store(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR_RW(sirq);
 
+static ssize_t sirq_polarity_show(struct device *dev,
+                                 struct device_attribute *attr, char *buf)
+{
+       struct aspeed_vuart *vuart = dev_get_drvdata(dev);
+       u8 reg;
+
+       reg = readb(vuart->regs + ASPEED_VUART_GCRA);
+       reg &= ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY;
+
+       return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg ? 1 : 0);
+}
+
+static void aspeed_vuart_set_sirq_polarity(struct aspeed_vuart *vuart,
+                                          bool polarity)
+{
+       u8 reg = readb(vuart->regs + ASPEED_VUART_GCRA);
+
+       if (polarity)
+               reg |= ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY;
+       else
+               reg &= ~ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY;
+
+       writeb(reg, vuart->regs + ASPEED_VUART_GCRA);
+}
+
+static ssize_t sirq_polarity_store(struct device *dev,
+                                  struct device_attribute *attr,
+                                  const char *buf, size_t count)
+{
+       struct aspeed_vuart *vuart = dev_get_drvdata(dev);
+       unsigned long val;
+       int err;
+
+       err = kstrtoul(buf, 0, &val);
+       if (err)
+               return err;
+
+       aspeed_vuart_set_sirq_polarity(vuart, val != 0);
+
+       return count;
+}
+
+static DEVICE_ATTR_RW(sirq_polarity);
+
 static struct attribute *aspeed_vuart_attrs[] = {
        &dev_attr_sirq.attr,
+       &dev_attr_sirq_polarity.attr,
        &dev_attr_lpc_address.attr,
        NULL,
 };
@@ -302,8 +350,30 @@ static int aspeed_vuart_handle_irq(struct uart_port *port)
        return 1;
 }
 
+static void aspeed_vuart_auto_configure_sirq_polarity(
+       struct aspeed_vuart *vuart, struct device_node *syscon_np,
+       u32 reg_offset, u32 reg_mask)
+{
+       struct regmap *regmap;
+       u32 value;
+
+       regmap = syscon_node_to_regmap(syscon_np);
+       if (IS_ERR(regmap)) {
+               dev_warn(vuart->dev,
+                        "could not get regmap for aspeed,sirq-polarity-sense\n");
+               return;
+       }
+       if (regmap_read(regmap, reg_offset, &value)) {
+               dev_warn(vuart->dev, "could not read hw strap table\n");
+               return;
+       }
+
+       aspeed_vuart_set_sirq_polarity(vuart, (value & reg_mask) == 0);
+}
+
 static int aspeed_vuart_probe(struct platform_device *pdev)
 {
+       struct of_phandle_args sirq_polarity_sense_args;
        struct uart_8250_port port;
        struct aspeed_vuart *vuart;
        struct device_node *np;
@@ -402,6 +472,20 @@ static int aspeed_vuart_probe(struct platform_device *pdev)
 
        vuart->line = rc;
 
+       rc = of_parse_phandle_with_fixed_args(
+               np, "aspeed,sirq-polarity-sense", 2, 0,
+               &sirq_polarity_sense_args);
+       if (rc < 0) {
+               dev_dbg(&pdev->dev,
+                       "aspeed,sirq-polarity-sense property not found\n");
+       } else {
+               aspeed_vuart_auto_configure_sirq_polarity(
+                       vuart, sirq_polarity_sense_args.np,
+                       sirq_polarity_sense_args.args[0],
+                       BIT(sirq_polarity_sense_args.args[1]));
+               of_node_put(sirq_polarity_sense_args.np);
+       }
+
        aspeed_vuart_set_enabled(vuart, true);
        aspeed_vuart_set_host_tx_discard(vuart, true);
        platform_set_drvdata(pdev, vuart);

diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 7ef60f8..771ac5d 100644 (file)
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -243,6 +243,7 @@ config SERIAL_8250_ASPEED_VUART
        tristate "Aspeed Virtual UART"
        depends on SERIAL_8250
        depends on OF
+       depends on REGMAP && MFD_SYSCON
        help
          If you want to use the virtual UART (VUART) device on Aspeed
          BMC platforms, enable this option. This enables the 16550A-