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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>
This commit is contained in:
Jeremy Kerr 2018-05-24 11:29:56 +08:00 committed by Benjamin Herrenschmidt
parent c49e34401a
commit 26d79b272d
1 changed files with 23 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
drivers/fsi/fsi-master-gpio.c
View File

@ -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 @@ static int poll_for_response(struct fsi_master_gpio *master,
"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 @@ static int poll_for_response(struct fsi_master_gpio *master,
*/
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 @@ static int poll_for_response(struct fsi_master_gpio *master,
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);