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Commit 26d79b27 authored by Jeremy Kerr's avatar Jeremy Kerr Committed by Benjamin Herrenschmidt
Browse files

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: default avatarJeremy Kerr <jk@ozlabs.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Tested-by: default avatarJoel Stanley <joel@jms.id.au>
parent c49e3440

drivers/fsi/fsi-master-gpio.c

+23 −25
Original line number Diff line number Diff line
@@ -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);