On Thu, Jan 03, 2019 at 04:23:38PM -0800, Sowjanya Komatineni wrote:
> Bus Clear feature of tegra i2c controller helps to recover from
> bus hang when i2c master loses the bus arbitration due to the
> slave device holding SDA LOW continuously for some unknown reasons.
>
> Signed-off-by: Sowjanya Komatineni <skomatineni@xxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-tegra.c | 65 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 65 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 437294ea2f0a..89a0c9fdc99e 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -63,6 +63,7 @@
> #define I2C_FIFO_STATUS_RX_SHIFT 0
> #define I2C_INT_MASK 0x064
> #define I2C_INT_STATUS 0x068
> +#define I2C_INT_BUS_CLR_DONE BIT(11)
> #define I2C_INT_PACKET_XFER_COMPLETE BIT(7)
> #define I2C_INT_ALL_PACKETS_XFER_COMPLETE BIT(6)
> #define I2C_INT_TX_FIFO_OVERFLOW BIT(5)
> @@ -105,6 +106,15 @@
> #define I2C_HEADER_MASTER_ADDR_SHIFT 12
> #define I2C_HEADER_SLAVE_ADDR_SHIFT 1
>
> +#define I2C_BUS_CLEAR_CNFG 0x084
> +#define I2C_BC_SCLK_THRESHOLD 9
> +#define I2C_BC_SCLK_THRESHOLD_SHIFT 16
> +#define I2C_BC_STOP_COND BIT(2)
> +#define I2C_BC_TERMINATE BIT(1)
> +#define I2C_BC_ENABLE BIT(0)
> +#define I2C_BUS_CLEAR_STATUS 0x088
> +#define I2C_BC_STATUS BIT(0)
> +
> #define I2C_CONFIG_LOAD 0x08C
> #define I2C_MSTR_CONFIG_LOAD BIT(0)
> #define I2C_SLV_CONFIG_LOAD BIT(1)
> @@ -154,6 +164,8 @@ enum msg_end_type {
> * @clk_divisor_std_fast_mode: Clock divisor in standard/fast mode. It is
> * applicable if there is no fast clock source i.e. single clock
> * source.
> + * @has_bus_clr_support: Bus Clear support to recover from bus hang during
> + * SDA stuck low from device for some unknown reasons.
Might as well spell out clr as clear in the name. Or maybe to make it
shorter, call it supports_bus_clear.
> */
>
> struct tegra_i2c_hw_feature {
> @@ -167,6 +179,7 @@ struct tegra_i2c_hw_feature {
> bool has_multi_master_mode;
> bool has_slcg_override_reg;
> bool has_mst_fifo;
> + bool has_bus_clr_support;
> };
>
> /**
> @@ -636,6 +649,9 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
> goto err;
> }
>
> + if (i2c_dev->hw->has_bus_clr_support && (status & I2C_INT_BUS_CLR_DONE))
> + goto err;
> +
This looks odd. If we support bus clear and the BUS_CLR_DONE interrupt
is set, shouldn't we still process all other potential interrupts? Or
was this meant to be inversed:
if (!i2c_dev->hw->supports_bus_clear && (status & I2C_INT_BUS_CLR_DONE)
?
> if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
> if (i2c_dev->msg_buf_remaining)
> tegra_i2c_empty_rx_fifo(i2c_dev);
> @@ -664,6 +680,8 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
> tegra_i2c_mask_irq(i2c_dev, I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
> I2C_INT_PACKET_XFER_COMPLETE | I2C_INT_TX_FIFO_DATA_REQ |
> I2C_INT_RX_FIFO_DATA_REQ);
> + if (i2c_dev->hw->has_bus_clr_support)
> + tegra_i2c_mask_irq(i2c_dev, I2C_INT_BUS_CLR_DONE);
> i2c_writel(i2c_dev, status, I2C_INT_STATUS);
> if (i2c_dev->is_dvc)
> dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
> @@ -674,6 +692,41 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
> return IRQ_HANDLED;
> }
>
> +static int tegra_i2c_issue_bus_clear(struct tegra_i2c_dev *i2c_dev)
> +{
> + int time_left, err;
> + u32 reg;
> +
> + if (i2c_dev->hw->has_bus_clr_support) {
> + reinit_completion(&i2c_dev->msg_complete);
> + reg = (I2C_BC_SCLK_THRESHOLD << I2C_BC_SCLK_THRESHOLD_SHIFT) |
> + I2C_BC_STOP_COND | I2C_BC_TERMINATE;
> + i2c_writel(i2c_dev, reg, I2C_BUS_CLEAR_CNFG);
> + if (i2c_dev->hw->has_config_load_reg) {
> + err = tegra_i2c_wait_for_config_load(i2c_dev);
> + if (err)
> + return err;
> + }
> + reg |= I2C_BC_ENABLE;
> + i2c_writel(i2c_dev, reg, I2C_BUS_CLEAR_CNFG);
> + tegra_i2c_unmask_irq(i2c_dev, I2C_INT_BUS_CLR_DONE);
> +
> + time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
> + TEGRA_I2C_TIMEOUT);
wait_for_completion_timeout() returns an unsigned long, so the type of
time_left should reflect that.
Thierry
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