diff options
| -rw-r--r-- | drivers/input/serio/ps2-gpio.c | 102 |
1 files changed, 82 insertions, 20 deletions
diff --git a/drivers/input/serio/ps2-gpio.c b/drivers/input/serio/ps2-gpio.c index 1682125fba11..f1b7313a0866 100644 --- a/drivers/input/serio/ps2-gpio.c +++ b/drivers/input/serio/ps2-gpio.c @@ -19,6 +19,7 @@ #include <linux/of.h> #include <linux/jiffies.h> #include <linux/delay.h> +#include <linux/timekeeping.h> #define DRIVER_NAME "ps2-gpio" @@ -44,6 +45,30 @@ #define PS2_CMD_RESEND 0xfe +/* + * The PS2 protocol specifies a clock frequency between 10kHz and 16.7kHz, + * therefore the maximal interrupt interval should be 100us and the minimum + * interrupt interval should be ~60us. Let's allow +/- 20us for frequency + * deviations and interrupt latency. + * + * The data line must be samples after ~30us to 50us after the falling edge, + * since the device updates the data line at the rising edge. + * + * ___ ______ ______ ______ ___ + * \ / \ / \ / \ / + * \ / \ / \ / \ / + * \______/ \______/ \______/ \______/ + * + * |-----------------| |--------| + * 60us/100us 30us/50us + */ +#define PS2_CLK_FREQ_MIN_HZ 10000 +#define PS2_CLK_FREQ_MAX_HZ 16700 +#define PS2_CLK_MIN_INTERVAL_US ((1000 * 1000) / PS2_CLK_FREQ_MAX_HZ) +#define PS2_CLK_MAX_INTERVAL_US ((1000 * 1000) / PS2_CLK_FREQ_MIN_HZ) +#define PS2_IRQ_MIN_INTERVAL_US (PS2_CLK_MIN_INTERVAL_US - 20) +#define PS2_IRQ_MAX_INTERVAL_US (PS2_CLK_MAX_INTERVAL_US + 20) + struct ps2_gpio_data { struct device *dev; struct serio *serio; @@ -52,6 +77,8 @@ struct ps2_gpio_data { struct gpio_desc *gpio_data; bool write_enable; int irq; + ktime_t t_irq_now; + ktime_t t_irq_last; struct { unsigned char cnt; unsigned char byte; @@ -59,6 +86,8 @@ struct ps2_gpio_data { struct { unsigned char cnt; unsigned char byte; + ktime_t t_xfer_start; + ktime_t t_xfer_end; struct completion complete; struct mutex mutex; struct delayed_work work; @@ -69,6 +98,9 @@ static int ps2_gpio_open(struct serio *serio) { struct ps2_gpio_data *drvdata = serio->port_data; + drvdata->t_irq_last = 0; + drvdata->tx.t_xfer_end = 0; + enable_irq(drvdata->irq); return 0; } @@ -122,6 +154,7 @@ static void ps2_gpio_tx_work_fn(struct work_struct *work) struct ps2_gpio_data, tx.work); + drvdata->tx.t_xfer_start = ktime_get(); enable_irq(drvdata->irq); gpiod_direction_output(drvdata->gpio_data, 0); gpiod_direction_input(drvdata->gpio_clk); @@ -132,20 +165,31 @@ static irqreturn_t ps2_gpio_irq_rx(struct ps2_gpio_data *drvdata) unsigned char byte, cnt; int data; int rxflags = 0; - static unsigned long old_jiffies; + s64 us_delta; byte = drvdata->rx.byte; cnt = drvdata->rx.cnt; - if (old_jiffies == 0) - old_jiffies = jiffies; + drvdata->t_irq_now = ktime_get(); + + /* + * We need to consider spurious interrupts happening right after + * a TX xfer finished. + */ + us_delta = ktime_us_delta(drvdata->t_irq_now, drvdata->tx.t_xfer_end); + if (unlikely(us_delta < PS2_IRQ_MIN_INTERVAL_US)) + goto end; - if ((jiffies - old_jiffies) > usecs_to_jiffies(100)) { + us_delta = ktime_us_delta(drvdata->t_irq_now, drvdata->t_irq_last); + if (us_delta > PS2_IRQ_MAX_INTERVAL_US && cnt) { dev_err(drvdata->dev, "RX: timeout, probably we missed an interrupt\n"); goto err; + } else if (unlikely(us_delta < PS2_IRQ_MIN_INTERVAL_US)) { + /* Ignore spurious IRQs. */ + goto end; } - old_jiffies = jiffies; + drvdata->t_irq_last = drvdata->t_irq_now; data = gpiod_get_value(drvdata->gpio_data); if (unlikely(data < 0)) { @@ -183,7 +227,8 @@ static irqreturn_t ps2_gpio_irq_rx(struct ps2_gpio_data *drvdata) goto err; } - /* Do not send spurious ACK's and NACK's when write fn is + /* + * Do not send spurious ACK's and NACK's when write fn is * not provided. */ if (!drvdata->write_enable) { @@ -193,7 +238,8 @@ static irqreturn_t ps2_gpio_irq_rx(struct ps2_gpio_data *drvdata) break; } - /* Let's send the data without waiting for the stop bit to be + /* + * Let's send the data without waiting for the stop bit to be * sent. It may happen that we miss the stop bit. When this * happens we have no way to recover from this, certainly * missing the parity bit would be recognized when processing @@ -209,7 +255,7 @@ static irqreturn_t ps2_gpio_irq_rx(struct ps2_gpio_data *drvdata) goto err; } cnt = byte = 0; - old_jiffies = 0; + goto end; /* success */ default: dev_err(drvdata->dev, "RX: got out of sync with the device\n"); @@ -221,7 +267,6 @@ static irqreturn_t ps2_gpio_irq_rx(struct ps2_gpio_data *drvdata) err: cnt = byte = 0; - old_jiffies = 0; __ps2_gpio_write(drvdata->serio, PS2_CMD_RESEND); end: drvdata->rx.cnt = cnt; @@ -233,20 +278,34 @@ static irqreturn_t ps2_gpio_irq_tx(struct ps2_gpio_data *drvdata) { unsigned char byte, cnt; int data; - static unsigned long old_jiffies; + s64 us_delta; cnt = drvdata->tx.cnt; byte = drvdata->tx.byte; - if (old_jiffies == 0) - old_jiffies = jiffies; + drvdata->t_irq_now = ktime_get(); + + /* + * There might be pending IRQs since we disabled IRQs in + * __ps2_gpio_write(). We can expect at least one clock period until + * the device generates the first falling edge after releasing the + * clock line. + */ + us_delta = ktime_us_delta(drvdata->t_irq_now, + drvdata->tx.t_xfer_start); + if (unlikely(us_delta < PS2_CLK_MIN_INTERVAL_US)) + goto end; - if ((jiffies - old_jiffies) > usecs_to_jiffies(100)) { + us_delta = ktime_us_delta(drvdata->t_irq_now, drvdata->t_irq_last); + if (us_delta > PS2_IRQ_MAX_INTERVAL_US && cnt > 1) { dev_err(drvdata->dev, "TX: timeout, probably we missed an interrupt\n"); goto err; + } else if (unlikely(us_delta < PS2_IRQ_MIN_INTERVAL_US)) { + /* Ignore spurious IRQs. */ + goto end; } - old_jiffies = jiffies; + drvdata->t_irq_last = drvdata->t_irq_now; switch (cnt) { case PS2_START_BIT: @@ -275,7 +334,8 @@ static irqreturn_t ps2_gpio_irq_tx(struct ps2_gpio_data *drvdata) gpiod_direction_input(drvdata->gpio_data); break; case PS2_TX_TIMEOUT: - /* Devices generate one extra clock pulse before sending the + /* + * Devices generate one extra clock pulse before sending the * acknowledgment. */ break; @@ -287,14 +347,15 @@ static irqreturn_t ps2_gpio_irq_tx(struct ps2_gpio_data *drvdata) goto err; } + drvdata->tx.t_xfer_end = ktime_get(); drvdata->mode = PS2_MODE_RX; complete(&drvdata->tx.complete); cnt = 1; - old_jiffies = 0; goto end; /* success */ default: - /* Probably we missed the stop bit. Therefore we release data + /* + * Probably we missed the stop bit. Therefore we release data * line and try again. */ gpiod_direction_input(drvdata->gpio_data); @@ -307,7 +368,6 @@ static irqreturn_t ps2_gpio_irq_tx(struct ps2_gpio_data *drvdata) err: cnt = 1; - old_jiffies = 0; gpiod_direction_input(drvdata->gpio_data); __ps2_gpio_write(drvdata->serio, drvdata->tx.byte); end: @@ -391,7 +451,8 @@ static int ps2_gpio_probe(struct platform_device *pdev) serio->id.type = SERIO_8042; serio->open = ps2_gpio_open; serio->close = ps2_gpio_close; - /* Write can be enabled in platform/dt data, but possibly it will not + /* + * Write can be enabled in platform/dt data, but possibly it will not * work because of the tough timings. */ serio->write = drvdata->write_enable ? ps2_gpio_write : NULL; @@ -404,7 +465,8 @@ static int ps2_gpio_probe(struct platform_device *pdev) drvdata->dev = dev; drvdata->mode = PS2_MODE_RX; - /* Tx count always starts at 1, as the start bit is sent implicitly by + /* + * Tx count always starts at 1, as the start bit is sent implicitly by * host-to-device communication initialization. */ drvdata->tx.cnt = 1; |