serial: sc16is7xx: split into core and I2C/SPI parts (sc16is7xx_lines)

Before, sc16is7xx_lines was checked for a free (zero) bit first, and then
later it was set only if UART port registration succeeded. Now that
sc16is7xx_lines is shared for the I2C and SPI drivers, there is a
possibility that the two drivers can simultaneously try to reserve the same
line bit at the same time.

To prevent this, make sure line allocation is reserved atomically, and use
a new variable to hold the status of UART port registration.

Now that we no longer need to search if a bit is set, it is now possible
to simplify sc16is7xx_lines allocation by using the IDA framework.

Link: https://lore.kernel.org/all/20231212150302.a9ec5d085a4ba65e89ca41af@hugovil.com/
Link: https://lore.kernel.org/all/CAHp75VebCZckUrNraYQj9k=Mrn2kbYs1Lx26f5-8rKJ3RXeh-w@mail.gmail.com/
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20240409154253.3043822-5-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 366eb3f537898a01cdee3346ad1c5ecfb3d2da68..9c9673243c4cb81c1e055645ebefedf358a0e36d 100644 (file)
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -10,12 +10,12 @@
 #undef DEFAULT_SYMBOL_NAMESPACE
 #define DEFAULT_SYMBOL_NAMESPACE SERIAL_NXP_SC16IS7XX
 
-#include <linux/bitops.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/export.h>
 #include <linux/gpio/driver.h>
+#include <linux/idr.h>
 #include <linux/kthread.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
@@ -345,7 +345,7 @@ struct sc16is7xx_port {
        struct sc16is7xx_one            p[];
 };
 
-static DECLARE_BITMAP(sc16is7xx_lines, SC16IS7XX_MAX_DEVS);
+static DEFINE_IDA(sc16is7xx_lines);
 
 static struct uart_driver sc16is7xx_uart = {
        .owner          = THIS_MODULE,
@@ -1462,6 +1462,7 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
        u32 uartclk = 0;
        int i, ret;
        struct sc16is7xx_port *s;
+       bool port_registered[SC16IS7XX_MAX_PORTS];
 
        for (i = 0; i < devtype->nr_uart; i++)
                if (IS_ERR(regmaps[i]))
@@ -1526,13 +1527,19 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
        regmap_write(regmaps[0], SC16IS7XX_IOCONTROL_REG,
                     SC16IS7XX_IOCONTROL_SRESET_BIT);
 
+       /* Mark each port line and status as uninitialised. */
        for (i = 0; i < devtype->nr_uart; ++i) {
-               s->p[i].port.line = find_first_zero_bit(sc16is7xx_lines,
-                                                       SC16IS7XX_MAX_DEVS);
-               if (s->p[i].port.line >= SC16IS7XX_MAX_DEVS) {
-                       ret = -ERANGE;
+               s->p[i].port.line = SC16IS7XX_MAX_DEVS;
+               port_registered[i] = false;
+       }
+
+       for (i = 0; i < devtype->nr_uart; ++i) {
+               ret = ida_alloc_max(&sc16is7xx_lines,
+                                   SC16IS7XX_MAX_DEVS - 1, GFP_KERNEL);
+               if (ret < 0)
                        goto out_ports;
-               }
+
+               s->p[i].port.line = ret;
 
                /* Initialize port data */
                s->p[i].port.dev        = dev;
@@ -1578,7 +1585,7 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
                if (ret)
                        goto out_ports;
 
-               set_bit(s->p[i].port.line, sc16is7xx_lines);
+               port_registered[i] = true;
 
                /* Enable EFR */
                sc16is7xx_port_write(&s->p[i].port, SC16IS7XX_LCR_REG,
@@ -1636,9 +1643,12 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
 #endif
 
 out_ports:
-       for (i = 0; i < devtype->nr_uart; i++)
-               if (test_and_clear_bit(s->p[i].port.line, sc16is7xx_lines))
+       for (i = 0; i < devtype->nr_uart; i++) {
+               if (s->p[i].port.line < SC16IS7XX_MAX_DEVS)
+                       ida_free(&sc16is7xx_lines, s->p[i].port.line);
+               if (port_registered[i])
                        uart_remove_one_port(&sc16is7xx_uart, &s->p[i].port);
+       }
 
        kthread_stop(s->kworker_task);
 
@@ -1661,7 +1671,7 @@ void sc16is7xx_remove(struct device *dev)
 
        for (i = 0; i < s->devtype->nr_uart; i++) {
                kthread_cancel_delayed_work_sync(&s->p[i].ms_work);
-               clear_bit(s->p[i].port.line, sc16is7xx_lines);
+               ida_free(&sc16is7xx_lines, s->p[i].port.line);
                uart_remove_one_port(&sc16is7xx_uart, &s->p[i].port);
                sc16is7xx_power(&s->p[i].port, 0);
        }