[PATCH 4/5] i2c: tegra: Add support for SW Mutex register

Kartik Rajput
2025-01-08T11:06:59Z

From: Akhil R <akhilrajeev@nvidia.com>

Add support for SW Mutex register introduced in Tegra264 to provide
an option to share the interface between multiple firmware and/or
Virtual Machines.

However, the hardware does not ensure any protection based on the
values. The driver/firmware should honor the peer who already holds
the mutex.

Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
Signed-off-by: Kartik Rajput <kkartik@nvidia.com>
---
drivers/i2c/busses/i2c-tegra.c | 126 +++++++++++++++++++++++++++++----
1 file changed, 111 insertions(+), 15 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index cf05937cb826..a5974af5b1af 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -135,6 +135,11 @@
#define I2C_MST_FIFO_STATUS_TX GENMASK(23, 16)
#define I2C_MST_FIFO_STATUS_RX GENMASK(7, 0)

+#define I2C_SW_MUTEX 0x0ec
+#define I2C_SW_MUTEX_REQUEST GENMASK(3, 0)
+#define I2C_SW_MUTEX_GRANT GENMASK(7, 4)
+#define I2C_SW_MUTEX_ID 9
+
/* configuration load timeout in microseconds */
#define I2C_CONFIG_LOAD_TIMEOUT 1000000

@@ -202,6 +207,7 @@ enum msg_end_type {
* in HS mode.
* @has_interface_timing_reg: Has interface timing register to program the tuned
* timing settings.
+ * @has_mutex: Has Mutex register for mutual exclusion with other firmwares or VM.
*/
struct tegra_i2c_hw_feature {
bool has_continue_xfer_support;
@@ -228,6 +234,7 @@ struct tegra_i2c_hw_feature {
u32 setup_hold_time_hs_mode;
bool has_interface_timing_reg;
bool has_hs_mode_support;
+ bool has_mutex;
};

/**
@@ -371,6 +378,99 @@ static void i2c_readsl(struct tegra_i2c_dev *i2c_dev, void *data,
readsl(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg), data, len);
}

+static int tegra_i2c_poll_register(struct tegra_i2c_dev *i2c_dev,
+ u32 reg, u32 mask, u32 delay_us,
+ u32 timeout_us)
+{
+ void __iomem *addr = i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg);
+ u32 val;
+
+ if (!i2c_dev->atomic_mode)
+ return readl_relaxed_poll_timeout(addr, val, !(val & mask),
+ delay_us, timeout_us);
+
+ return readl_relaxed_poll_timeout_atomic(addr, val, !(val & mask),
+ delay_us, timeout_us);
+}
+
+static int tegra_i2c_mutex_trylock(struct tegra_i2c_dev *i2c_dev)
+{
+ u32 val, id;
+
+ val = i2c_readl(i2c_dev, I2C_SW_MUTEX);
+ id = FIELD_GET(I2C_SW_MUTEX_GRANT, val);
+ if (id != 0)
+ return 0;
+
+ val = FIELD_PREP(I2C_SW_MUTEX_REQUEST, I2C_SW_MUTEX_ID);
+ i2c_writel(i2c_dev, val, I2C_SW_MUTEX);
+
+ val = i2c_readl(i2c_dev, I2C_SW_MUTEX);
+ id = FIELD_GET(I2C_SW_MUTEX_GRANT, val);
+
+ if (id != I2C_SW_MUTEX_ID)
+ return 0;
+
+ return 1;
+}
+
+static void tegra_i2c_mutex_lock(struct tegra_i2c_dev *i2c_dev)
+{
+ /* Poll until mutex is acquired. */
+ while (tegra_i2c_mutex_trylock(i2c_dev))
+ cpu_relax();
+}
+
+static void tegra_i2c_mutex_unlock(struct tegra_i2c_dev *i2c_dev)
+{
+ u32 val, id;
+
+ val = i2c_readl(i2c_dev, I2C_SW_MUTEX);
+ id = FIELD_GET(I2C_SW_MUTEX_GRANT, val);
+
+ if (WARN_ON(id != I2C_SW_MUTEX_ID))
+ return;
+
+ i2c_writel(i2c_dev, 0, I2C_SW_MUTEX);
+}
+
+static void tegra_i2c_bus_lock(struct i2c_adapter *adapter,
+ unsigned int flags)
+{
+ struct tegra_i2c_dev *i2c_dev = i2c_get_adapdata(adapter);
+
+ rt_mutex_lock_nested(&adapter->bus_lock, i2c_adapter_depth(adapter));
+ tegra_i2c_mutex_lock(i2c_dev);
+}
+
+static int tegra_i2c_bus_trylock(struct i2c_adapter *adapter,
+ unsigned int flags)
+{
+ struct tegra_i2c_dev *i2c_dev = i2c_get_adapdata(adapter);
+ int ret;
+
+ ret = rt_mutex_trylock(&adapter->bus_lock);
+ if (ret)
+ ret = tegra_i2c_mutex_trylock(i2c_dev);
+
+ return ret;
+}
+
+static void tegra_i2c_bus_unlock(struct i2c_adapter *adapter,
+ unsigned int flags)
+{
+ struct tegra_i2c_dev *i2c_dev = i2c_get_adapdata(adapter);
+
+ rt_mutex_unlock(&adapter->bus_lock);
+ tegra_i2c_mutex_unlock(i2c_dev);
+}
+
+static const struct i2c_lock_operations tegra_i2c_lock_ops = {
+ .lock_bus = tegra_i2c_bus_lock,
+ .trylock_bus = tegra_i2c_bus_trylock,
+ .unlock_bus = tegra_i2c_bus_unlock,
+};
+
static void tegra_i2c_mask_irq(struct tegra_i2c_dev *i2c_dev, u32 mask)
{
u32 int_mask;
@@ -546,21 +646,6 @@ static void tegra_i2c_vi_init(struct tegra_i2c_dev *i2c_dev)
i2c_writel(i2c_dev, 0x0, I2C_TLOW_SEXT);
}

-static int tegra_i2c_poll_register(struct tegra_i2c_dev *i2c_dev,
- u32 reg, u32 mask, u32 delay_us,
- u32 timeout_us)
-{
- void __iomem *addr = i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg);
- u32 val;
-
- if (!i2c_dev->atomic_mode)
- return readl_relaxed_poll_timeout(addr, val, !(val & mask),
- delay_us, timeout_us);
-
- return readl_relaxed_poll_timeout_atomic(addr, val, !(val & mask),
- delay_us, timeout_us);
-}
-
static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
{
u32 mask, val, offset;
@@ -1497,6 +1582,7 @@ static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
.setup_hold_time_fast_fast_plus_mode = 0x0,
.setup_hold_time_hs_mode = 0x0,
.has_interface_timing_reg = false,
+ .has_mutex = false,
};

static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
@@ -1521,6 +1607,7 @@ static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
.setup_hold_time_fast_fast_plus_mode = 0x0,
.setup_hold_time_hs_mode = 0x0,
.has_interface_timing_reg = false,
+ .has_mutex = false,
};

static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
@@ -1545,6 +1632,7 @@ static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
.setup_hold_time_fast_fast_plus_mode = 0x0,
.setup_hold_time_hs_mode = 0x0,
.has_interface_timing_reg = false,
+ .has_mutex = false,
};

static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
@@ -1569,6 +1657,7 @@ static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
.setup_hold_time_fast_fast_plus_mode = 0x0,
.setup_hold_time_hs_mode = 0x0,
.has_interface_timing_reg = true,
+ .has_mutex = false,
};

static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
@@ -1593,6 +1682,7 @@ static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
.setup_hold_time_fast_fast_plus_mode = 0,
.setup_hold_time_hs_mode = 0,
.has_interface_timing_reg = true,
+ .has_mutex = false,
};

static const struct tegra_i2c_hw_feature tegra186_i2c_hw = {
@@ -1617,6 +1707,7 @@ static const struct tegra_i2c_hw_feature tegra186_i2c_hw = {
.setup_hold_time_fast_fast_plus_mode = 0,
.setup_hold_time_hs_mode = 0,
.has_interface_timing_reg = true,
+ .has_mutex = false,
};

static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
@@ -1644,6 +1735,7 @@ static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
.setup_hold_time_hs_mode = 0x090909,
.has_interface_timing_reg = true,
.has_hs_mode_support = true,
+ .has_mutex = false,
};

static const struct tegra_i2c_hw_feature tegra264_i2c_hw = {
@@ -1671,6 +1763,7 @@ static const struct tegra_i2c_hw_feature tegra264_i2c_hw = {
.setup_hold_time_hs_mode = 0x090909,
.has_interface_timing_reg = true,
.has_hs_mode_support = true,
+ .has_mutex = true,
};

static const struct of_device_id tegra_i2c_of_match[] = {
@@ -1875,6 +1968,9 @@ static int tegra_i2c_probe(struct platform_device *pdev)
i2c_dev->adapter.nr = pdev->id;
ACPI_COMPANION_SET(&i2c_dev->adapter.dev, ACPI_COMPANION(&pdev->dev));

+ if (i2c_dev->hw->has_mutex)
+ i2c_dev->adapter.lock_ops = &tegra_i2c_lock_ops;
+
if (i2c_dev->hw->supports_bus_clear)
i2c_dev->adapter.bus_recovery_info = &tegra_i2c_recovery_info;

--
2.43.0