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Message-Id: <20211112133956.655179-2-minyard@acm.org>
Date: Fri, 12 Nov 2021 07:39:55 -0600
From: minyard@....org
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Pengutronix Kernel Team <kernel@...gutronix.de>,
linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
Corey Minyard <minyard@....org>,
Andrew Manley <andrew.manley@...lingtech.com>
Subject: [PATCH v2 1/2] i2c:imx: Add timer for handling the stop condition
From: Corey Minyard <minyard@....org>
Most IMX I2C interfaces don't generate an interrupt on a stop condition,
so it won't generate a timely stop event on a slave mode transfer.
Some users, like IPMB, need a timely stop event to work properly.
So, add a timer and add the proper handling to generate a stop event in
slave mode if the interface goes idle.
Signed-off-by: Corey Minyard <minyard@....org>
Tested-by: Andrew Manley <andrew.manley@...lingtech.com>
Reviewed-by: Andrew Manley <andrew.manley@...lingtech.com>
Reviewed-by: Oleksij Rempel <o.rempel@...gutronix.de>
---
drivers/i2c/busses/i2c-imx.c | 92 ++++++++++++++++++++++++++++--------
1 file changed, 73 insertions(+), 19 deletions(-)
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 3576b63a6c03..27f969b3dc07 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -37,6 +37,8 @@
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/hrtimer.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
@@ -51,6 +53,8 @@
/* This will be the driver name the kernel reports */
#define DRIVER_NAME "imx-i2c"
+#define I2C_IMX_CHECK_DELAY 30000 /* Time to check for bus idle, in NS */
+
/*
* Enable DMA if transfer byte size is bigger than this threshold.
* As the hardware request, it must bigger than 4 bytes.\
@@ -210,6 +214,10 @@ struct imx_i2c_struct {
struct imx_i2c_dma *dma;
struct i2c_client *slave;
enum i2c_slave_event last_slave_event;
+
+ /* For checking slave events. */
+ spinlock_t slave_lock;
+ struct hrtimer slave_timer;
};
static const struct imx_i2c_hwdata imx1_i2c_hwdata = {
@@ -680,7 +688,7 @@ static void i2c_imx_slave_event(struct imx_i2c_struct *i2c_imx,
static void i2c_imx_slave_finish_op(struct imx_i2c_struct *i2c_imx)
{
- u8 val;
+ u8 val = 0;
while (i2c_imx->last_slave_event != I2C_SLAVE_STOP) {
switch (i2c_imx->last_slave_event) {
@@ -701,10 +709,11 @@ static void i2c_imx_slave_finish_op(struct imx_i2c_struct *i2c_imx)
}
}
-static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx,
- unsigned int status, unsigned int ctl)
+/* Returns true if the timer should be restarted, false if not. */
+static irqreturn_t i2c_imx_slave_handle(struct imx_i2c_struct *i2c_imx,
+ unsigned int status, unsigned int ctl)
{
- u8 value;
+ u8 value = 0;
if (status & I2SR_IAL) { /* Arbitration lost */
i2c_imx_clear_irq(i2c_imx, I2SR_IAL);
@@ -712,6 +721,16 @@ static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx,
return IRQ_HANDLED;
}
+ if (!(status & I2SR_IBB)) {
+ /* No master on the bus, that could mean a stop condition. */
+ i2c_imx_slave_finish_op(i2c_imx);
+ return IRQ_HANDLED;
+ }
+
+ if (!(status & I2SR_ICF))
+ /* Data transfer still in progress, ignore this. */
+ goto out;
+
if (status & I2SR_IAAS) { /* Addressed as a slave */
i2c_imx_slave_finish_op(i2c_imx);
if (status & I2SR_SRW) { /* Master wants to read from us*/
@@ -737,16 +756,9 @@ static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx,
imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
}
} else if (!(ctl & I2CR_MTX)) { /* Receive mode */
- if (status & I2SR_IBB) { /* No STOP signal detected */
- value = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
- i2c_imx_slave_event(i2c_imx,
- I2C_SLAVE_WRITE_RECEIVED, &value);
- } else { /* STOP signal is detected */
- dev_dbg(&i2c_imx->adapter.dev,
- "STOP signal detected");
- i2c_imx_slave_event(i2c_imx,
- I2C_SLAVE_STOP, &value);
- }
+ value = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
+ i2c_imx_slave_event(i2c_imx,
+ I2C_SLAVE_WRITE_RECEIVED, &value);
} else if (!(status & I2SR_RXAK)) { /* Transmit mode received ACK */
ctl |= I2CR_MTX;
imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
@@ -755,15 +767,43 @@ static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx,
I2C_SLAVE_READ_PROCESSED, &value);
imx_i2c_write_reg(value, i2c_imx, IMX_I2C_I2DR);
- } else { /* Transmit mode received NAK */
+ } else { /* Transmit mode received NAK, operation is done */
ctl &= ~I2CR_MTX;
imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
+ i2c_imx_slave_finish_op(i2c_imx);
+ return IRQ_HANDLED;
}
+out:
+ /*
+ * No need to check the return value here. If it returns 0 or
+ * 1, then everything is fine. If it returns -1, then the
+ * timer is running in the handler. This will still work,
+ * though it may be redone (or already have been done) by the
+ * timer function.
+ */
+ hrtimer_try_to_cancel(&i2c_imx->slave_timer);
+ hrtimer_forward_now(&i2c_imx->slave_timer, I2C_IMX_CHECK_DELAY);
+ hrtimer_restart(&i2c_imx->slave_timer);
return IRQ_HANDLED;
}
+static enum hrtimer_restart i2c_imx_slave_timeout(struct hrtimer *t)
+{
+ struct imx_i2c_struct *i2c_imx = container_of(t, struct imx_i2c_struct,
+ slave_timer);
+ unsigned int ctl, status;
+ unsigned long flags;
+
+ spin_lock_irqsave(&i2c_imx->slave_lock, flags);
+ status = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
+ ctl = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+ i2c_imx_slave_handle(i2c_imx, status, ctl);
+ spin_unlock_irqrestore(&i2c_imx->slave_lock, flags);
+ return HRTIMER_NORESTART;
+}
+
static void i2c_imx_slave_init(struct imx_i2c_struct *i2c_imx)
{
int temp;
@@ -843,7 +883,9 @@ static irqreturn_t i2c_imx_isr(int irq, void *dev_id)
{
struct imx_i2c_struct *i2c_imx = dev_id;
unsigned int ctl, status;
+ unsigned long flags;
+ spin_lock_irqsave(&i2c_imx->slave_lock, flags);
status = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
ctl = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
@@ -851,14 +893,20 @@ static irqreturn_t i2c_imx_isr(int irq, void *dev_id)
i2c_imx_clear_irq(i2c_imx, I2SR_IIF);
if (i2c_imx->slave) {
if (!(ctl & I2CR_MSTA)) {
- return i2c_imx_slave_isr(i2c_imx, status, ctl);
- } else if (i2c_imx->last_slave_event !=
- I2C_SLAVE_STOP) {
- i2c_imx_slave_finish_op(i2c_imx);
+ irqreturn_t ret;
+
+ ret = i2c_imx_slave_handle(i2c_imx,
+ status, ctl);
+ spin_unlock_irqrestore(&i2c_imx->slave_lock,
+ flags);
+ return ret;
}
+ i2c_imx_slave_finish_op(i2c_imx);
}
+ spin_unlock_irqrestore(&i2c_imx->slave_lock, flags);
return i2c_imx_master_isr(i2c_imx, status);
}
+ spin_unlock_irqrestore(&i2c_imx->slave_lock, flags);
return IRQ_NONE;
}
@@ -1378,6 +1426,10 @@ static int i2c_imx_probe(struct platform_device *pdev)
if (!i2c_imx)
return -ENOMEM;
+ spin_lock_init(&i2c_imx->slave_lock);
+ hrtimer_init(&i2c_imx->slave_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+ i2c_imx->slave_timer.function = i2c_imx_slave_timeout;
+
match = device_get_match_data(&pdev->dev);
if (match)
i2c_imx->hwdata = match;
@@ -1491,6 +1543,8 @@ static int i2c_imx_remove(struct platform_device *pdev)
if (ret < 0)
return ret;
+ hrtimer_cancel(&i2c_imx->slave_timer);
+
/* remove adapter */
dev_dbg(&i2c_imx->adapter.dev, "adapter removed\n");
i2c_del_adapter(&i2c_imx->adapter);
--
2.25.1
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