fsi/master-gpio: Replace bit_bit lock with IRQ disable/enable

We currently use a spinlock (bit_lock) around operations that clock bits
out of the FSI bus, and a mutex to protect against simultaneous access
to the master.

This means that bit_lock isn't needed for mutual exlusion, only to
prevent timing issues when clocking bits out.

To reflect this, this change converts bit_lock to just the
local_irq_save/restore operation.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Tested-by: Joel Stanley <joel@jms.id.au>

diff --git a/drivers/fsi/fsi-master-gpio.c b/drivers/fsi/fsi-master-gpio.c
index da556da..084e9da 100644 (file)
--- a/drivers/fsi/fsi-master-gpio.c
+++ b/drivers/fsi/fsi-master-gpio.c
@@ -8,11 +8,11 @@
 #include <linux/fsi.h>
 #include <linux/gpio/consumer.h>
 #include <linux/io.h>
+#include <linux/irqflags.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
-#include <linux/spinlock.h>
 
 #include "fsi-master.h"
 
@@ -56,7 +56,6 @@ struct fsi_master_gpio {
        struct fsi_master       master;
        struct device           *dev;
        struct mutex            cmd_lock;       /* mutex for command ordering */
-       spinlock_t              bit_lock;       /* lock for clocking bits out */
        struct gpio_desc        *gpio_clk;
        struct gpio_desc        *gpio_data;
        struct gpio_desc        *gpio_trans;    /* Voltage translator */
@@ -367,7 +366,7 @@ static int read_one_response(struct fsi_master_gpio *master,
        uint8_t tag;
        int i;
 
-       spin_lock_irqsave(&master->bit_lock, flags);
+       local_irq_save(flags);
 
        /* wait for the start bit */
        for (i = 0; i < FSI_GPIO_MTOE_COUNT; i++) {
@@ -380,7 +379,7 @@ static int read_one_response(struct fsi_master_gpio *master,
        if (i == FSI_GPIO_MTOE_COUNT) {
                dev_dbg(master->dev,
                        "Master time out waiting for response\n");
-               spin_unlock_irqrestore(&master->bit_lock, flags);
+               local_irq_restore(flags);
                return -ETIMEDOUT;
        }
 
@@ -399,7 +398,7 @@ static int read_one_response(struct fsi_master_gpio *master,
        /* read CRC */
        serial_in(master, &msg, FSI_GPIO_CRC_SIZE);
 
-       spin_unlock_irqrestore(&master->bit_lock, flags);
+       local_irq_restore(flags);
 
        /* we have a whole message now; check CRC */
        crc = crc4(0, 1, 1);
@@ -430,10 +429,10 @@ static int issue_term(struct fsi_master_gpio *master, uint8_t slave)
 
        build_term_command(&cmd, slave);
 
-       spin_lock_irqsave(&master->bit_lock, flags);
+       local_irq_save(flags);
        serial_out(master, &cmd);
        echo_delay(master);
-       spin_unlock_irqrestore(&master->bit_lock, flags);
+       local_irq_restore(flags);
 
        rc = read_one_response(master, 0, NULL, &tag);
        if (rc < 0) {
@@ -475,11 +474,11 @@ retry:
                         "CRC error retry %d\n", crc_err_retries);
                trace_fsi_master_gpio_crc_rsp_error(master);
                build_epoll_command(&cmd, slave);
-               spin_lock_irqsave(&master->bit_lock, flags);
+               local_irq_save(flags);
                clock_zeros(master, FSI_GPIO_EPOLL_CLOCKS);
                serial_out(master, &cmd);
                echo_delay(master);
-               spin_unlock_irqrestore(&master->bit_lock, flags);
+               local_irq_restore(flags);
                goto retry;
        } else if (rc)
                goto fail;
@@ -506,18 +505,18 @@ retry:
                 */
                if (busy_count++ < FSI_GPIO_MAX_BUSY) {
                        build_dpoll_command(&cmd, slave);
-                       spin_lock_irqsave(&master->bit_lock, flags);
+                       local_irq_save(flags);
                        clock_zeros(master, FSI_GPIO_DPOLL_CLOCKS);
                        serial_out(master, &cmd);
                        echo_delay(master);
-                       spin_unlock_irqrestore(&master->bit_lock, flags);
+                       local_irq_restore(flags);
                        goto retry;
                }
                dev_warn(master->dev,
                        "ERR slave is stuck in busy state, issuing TERM\n");
-               spin_lock_irqsave(&master->bit_lock, flags);
+               local_irq_save(flags);
                clock_zeros(master, FSI_GPIO_DPOLL_CLOCKS);
-               spin_unlock_irqrestore(&master->bit_lock, flags);
+               local_irq_restore(flags);
                issue_term(master, slave);
                rc = -EIO;
                break;
@@ -537,9 +536,10 @@ retry:
                trace_fsi_master_gpio_poll_response_busy(master, busy_count);
  fail:
        /* Clock the slave enough to be ready for next operation */
-       spin_lock_irqsave(&master->bit_lock, flags);
+       local_irq_save(flags);
        clock_zeros(master, FSI_GPIO_PRIME_SLAVE_CLOCKS);
-       spin_unlock_irqrestore(&master->bit_lock, flags);
+       local_irq_restore(flags);
+
        return rc;
 }
 
@@ -548,15 +548,13 @@ static int send_request(struct fsi_master_gpio *master,
 {
        unsigned long flags;
 
-       spin_lock_irqsave(&master->bit_lock, flags);
-       if (master->external_mode) {
-               spin_unlock_irqrestore(&master->bit_lock, flags);
+       if (master->external_mode)
                return -EBUSY;
-       }
 
+       local_irq_save(flags);
        serial_out(master, cmd);
        echo_delay(master);
-       spin_unlock_irqrestore(&master->bit_lock, flags);
+       local_irq_restore(flags);
 
        return 0;
 }
@@ -656,7 +654,7 @@ static int fsi_master_gpio_break(struct fsi_master *_master, int link)
                return -EBUSY;
        }
 
-       spin_lock_irqsave(&master->bit_lock, flags);
+       local_irq_save(flags);
 
        set_sda_output(master, 1);
        sda_out(master, 1);
@@ -667,7 +665,8 @@ static int fsi_master_gpio_break(struct fsi_master *_master, int link)
        sda_out(master, 1);
        clock_toggle(master, FSI_POST_BREAK_CLOCKS);
 
-       spin_unlock_irqrestore(&master->bit_lock, flags);
+       local_irq_restore(flags);
+
        last_address_update(master, 0, false, 0);
        mutex_unlock(&master->cmd_lock);
 
@@ -688,9 +687,9 @@ static void fsi_master_gpio_init(struct fsi_master_gpio *master)
        gpiod_direction_output(master->gpio_data, 1);
 
        /* todo: evaluate if clocks can be reduced */
-       spin_lock_irqsave(&master->bit_lock, flags);
+       local_irq_save(flags);
        clock_zeros(master, FSI_INIT_CLOCKS);
-       spin_unlock_irqrestore(&master->bit_lock, flags);
+       local_irq_restore(flags);
 }
 
 static void fsi_master_gpio_init_external(struct fsi_master_gpio *master)
@@ -832,7 +831,6 @@ static int fsi_master_gpio_probe(struct platform_device *pdev)
        master->master.send_break = fsi_master_gpio_break;
        master->master.link_enable = fsi_master_gpio_link_enable;
        platform_set_drvdata(pdev, master);
-       spin_lock_init(&master->bit_lock);
        mutex_init(&master->cmd_lock);
 
        fsi_master_gpio_init(master);