[PATCH v3] i2c: bcm-iproc: Add i2c recovery support

Chris Packham
2021-06-03T05:25:25Z

From: Richard Laing <richard.laing@alliedtelesis.co.nz>

The bcm-iproc controller can put the SDA/SCL lines into bit-bang mode,
make use of this to support i2c bus recovery.

Signed-off-by: Richard Laing <richard.laing@alliedtelesis.co.nz>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
Richard did most of the work on this. I'm just cleaning it up to get it
upstream.

Changes in v3:
- drop const from bcm_iproc_recovery_info due to build error from the
kernel test bot

Changes in v2:
- Incorporate feedback from Ray Jui
- Move bcm_iproc_i2c_resume so it can be re-used to return the i2c bus
to normal operation at the correct speed after a recovery.
- Add iproc_i2c_lockup_recover() helper to only trigger recovery if sda
is actually stuck
- Use usleep_range() instead of udelay()
- Cosmetic changes to register bit definitions

drivers/i2c/busses/i2c-bcm-iproc.c | 176 +++++++++++++++++++++++++----
1 file changed, 151 insertions(+), 25 deletions(-)

diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
index cceaf69279a9..fdbb98a848e3 100644
--- a/drivers/i2c/busses/i2c-bcm-iproc.c
+++ b/drivers/i2c/busses/i2c-bcm-iproc.c
@@ -25,6 +25,7 @@
#define CFG_OFFSET 0x00
#define CFG_RESET_SHIFT 31
#define CFG_EN_SHIFT 30
+#define CFG_BIT_BANG_SHIFT 29
#define CFG_SLAVE_ADDR_0_SHIFT 28
#define CFG_M_RETRY_CNT_SHIFT 16
#define CFG_M_RETRY_CNT_MASK 0x0f
@@ -66,6 +67,12 @@
#define S_FIFO_RX_THLD_SHIFT 8
#define S_FIFO_RX_THLD_MASK 0x3f

+#define M_BB_CTRL_OFFSET 0x14
+#define M_BB_SMBCLK_IN_SHIFT 31
+#define M_BB_SMBCLK_OUT_EN_SHIFT 30
+#define M_BB_SMBDAT_IN_SHIFT 29
+#define M_BB_SMBDAT_OUT_EN_SHIFT 28
+
#define M_CMD_OFFSET 0x30
#define M_CMD_START_BUSY_SHIFT 31
#define M_CMD_STATUS_SHIFT 25
@@ -713,6 +720,147 @@ static void bcm_iproc_i2c_enable_disable(struct bcm_iproc_i2c_dev *iproc_i2c,
iproc_i2c_wr_reg(iproc_i2c, CFG_OFFSET, val);
}

+static int bcm_iproc_i2c_resume(struct device *dev)
+{
+ struct bcm_iproc_i2c_dev *iproc_i2c = dev_get_drvdata(dev);
+ int ret;
+ u32 val;
+
+ /*
+ * Power domain could have been shut off completely in system deep
+ * sleep, so re-initialize the block here
+ */
+ ret = bcm_iproc_i2c_init(iproc_i2c);
+ if (ret)
+ return ret;
+
+ /* configure to the desired bus speed */
+ val = iproc_i2c_rd_reg(iproc_i2c, TIM_CFG_OFFSET);
+ val &= ~BIT(TIM_CFG_MODE_400_SHIFT);
+ val |= (iproc_i2c->bus_speed == I2C_MAX_FAST_MODE_FREQ) << TIM_CFG_MODE_400_SHIFT;
+ iproc_i2c_wr_reg(iproc_i2c, TIM_CFG_OFFSET, val);
+
+ bcm_iproc_i2c_enable_disable(iproc_i2c, true);
+
+ return 0;
+}
+
+static void bcm_iproc_i2c_prepare_recovery(struct i2c_adapter *adap)
+{
+ struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
+ u32 tmp;
+
+ dev_dbg(iproc_i2c->device, "Prepare recovery\n");
+
+ /* Disable interrupts */
+ writel(0, iproc_i2c->base + IE_OFFSET);
+ readl(iproc_i2c->base + IE_OFFSET);
+ synchronize_irq(iproc_i2c->irq);
+
+ /* Place controller in reset */
+ tmp = readl(iproc_i2c->base + CFG_OFFSET);
+ tmp |= BIT(CFG_RESET_SHIFT);
+ writel(tmp, iproc_i2c->base + CFG_OFFSET);
+ usleep_range(100, 200);
+
+ /* Switch to bit-bang mode */
+ tmp = readl(iproc_i2c->base + CFG_OFFSET);
+ tmp |= BIT(CFG_BIT_BANG_SHIFT);
+ writel(tmp, iproc_i2c->base + CFG_OFFSET);
+ usleep_range(100, 200);
+}
+
+static void bcm_iproc_i2c_unprepare_recovery(struct i2c_adapter *adap)
+{
+ struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
+ u32 tmp;
+
+ /* Switch to normal mode */
+ tmp = readl(iproc_i2c->base + CFG_OFFSET);
+ tmp &= ~BIT(CFG_BIT_BANG_SHIFT);
+ writel(tmp, iproc_i2c->base + CFG_OFFSET);
+ usleep_range(100, 200);
+
+ bcm_iproc_i2c_resume(iproc_i2c->device);
+
+ dev_dbg(iproc_i2c->device, "Recovery complete\n");
+}
+
+static int bcm_iproc_i2c_get_scl(struct i2c_adapter *adap)
+{
+ struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
+ u32 tmp;
+
+ tmp = readl(iproc_i2c->base + M_BB_CTRL_OFFSET);
+
+ return !!(tmp & BIT(M_BB_SMBCLK_IN_SHIFT));
+}
+
+static void bcm_iproc_i2c_set_scl(struct i2c_adapter *adap, int val)
+{
+ struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
+ u32 tmp;
+
+ tmp = readl(iproc_i2c->base + M_BB_CTRL_OFFSET);
+ if (val)
+ tmp |= BIT(M_BB_SMBCLK_OUT_EN_SHIFT);
+ else
+ tmp &= ~BIT(M_BB_SMBCLK_OUT_EN_SHIFT);
+
+ writel(tmp, iproc_i2c->base + M_BB_CTRL_OFFSET);
+}
+
+static void bcm_iproc_i2c_set_sda(struct i2c_adapter *adap, int val)
+{
+ struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
+ u32 tmp;
+
+ tmp = readl(iproc_i2c->base + M_BB_CTRL_OFFSET);
+ if (val)
+ tmp |= BIT(M_BB_SMBDAT_OUT_EN_SHIFT);
+ else
+ tmp &= ~BIT(M_BB_SMBDAT_OUT_EN_SHIFT);
+
+ writel(tmp, iproc_i2c->base + M_BB_CTRL_OFFSET);
+}
+
+static int bcm_iproc_i2c_get_sda(struct i2c_adapter *adap)
+{
+ struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
+ u32 tmp;
+
+ tmp = readl(iproc_i2c->base + M_BB_CTRL_OFFSET);
+
+ return !!(tmp & BIT(M_BB_SMBDAT_IN_SHIFT));
+}
+
+/* Check if bus lockup occurred, and invoke recovery if so. */
+static void iproc_i2c_lockup_recover(struct bcm_iproc_i2c_dev *iproc_i2c)
+{
+ /*
+ * assume bus lockup if SDA line is low;
+ * note that there is no need to switch to
+ * bit-bang mode for this check.
+ */
+ if (!bcm_iproc_i2c_get_sda(&iproc_i2c->adapter)) {
+ /* locked up - invoke i2c bus recovery. */
+ int ret = i2c_recover_bus(&iproc_i2c->adapter);
+
+ if (ret)
+ dev_err(iproc_i2c->device, "bus recovery: error %d\n", ret);
+ }
+}
+
+static struct i2c_bus_recovery_info bcm_iproc_recovery_info = {
+ .recover_bus = i2c_generic_scl_recovery,
+ .prepare_recovery = bcm_iproc_i2c_prepare_recovery,
+ .unprepare_recovery = bcm_iproc_i2c_unprepare_recovery,
+ .set_scl = bcm_iproc_i2c_set_scl,
+ .get_scl = bcm_iproc_i2c_get_scl,
+ .set_sda = bcm_iproc_i2c_set_sda,
+ .get_sda = bcm_iproc_i2c_get_sda,
+};
+
static int bcm_iproc_i2c_check_status(struct bcm_iproc_i2c_dev *iproc_i2c,
struct i2c_msg *msg)
{
@@ -806,6 +954,7 @@ static int bcm_iproc_i2c_xfer_wait(struct bcm_iproc_i2c_dev *iproc_i2c,
/* flush both TX/RX FIFOs */
val = BIT(M_FIFO_RX_FLUSH_SHIFT) | BIT(M_FIFO_TX_FLUSH_SHIFT);
iproc_i2c_wr_reg(iproc_i2c, M_FIFO_CTRL_OFFSET, val);
+ iproc_i2c_lockup_recover(iproc_i2c);
return -ETIMEDOUT;
}

@@ -814,6 +963,7 @@ static int bcm_iproc_i2c_xfer_wait(struct bcm_iproc_i2c_dev *iproc_i2c,
/* flush both TX/RX FIFOs */
val = BIT(M_FIFO_RX_FLUSH_SHIFT) | BIT(M_FIFO_TX_FLUSH_SHIFT);
iproc_i2c_wr_reg(iproc_i2c, M_FIFO_CTRL_OFFSET, val);
+ iproc_i2c_lockup_recover(iproc_i2c);
return ret;
}

@@ -1111,6 +1261,7 @@ static int bcm_iproc_i2c_probe(struct platform_device *pdev)
of_node_full_name(iproc_i2c->device->of_node));
adap->algo = &bcm_iproc_algo;
adap->quirks = &bcm_iproc_i2c_quirks;
+ adap->bus_recovery_info = &bcm_iproc_recovery_info;
adap->dev.parent = &pdev->dev;
adap->dev.of_node = pdev->dev.of_node;

@@ -1159,31 +1310,6 @@ static int bcm_iproc_i2c_suspend(struct device *dev)
return 0;
}

-static int bcm_iproc_i2c_resume(struct device *dev)
-{
- struct bcm_iproc_i2c_dev *iproc_i2c = dev_get_drvdata(dev);
- int ret;
- u32 val;
-
- /*
- * Power domain could have been shut off completely in system deep
- * sleep, so re-initialize the block here
- */
- ret = bcm_iproc_i2c_init(iproc_i2c);
- if (ret)
- return ret;
-
- /* configure to the desired bus speed */
- val = iproc_i2c_rd_reg(iproc_i2c, TIM_CFG_OFFSET);
- val &= ~BIT(TIM_CFG_MODE_400_SHIFT);
- val |= (iproc_i2c->bus_speed == I2C_MAX_FAST_MODE_FREQ) << TIM_CFG_MODE_400_SHIFT;
- iproc_i2c_wr_reg(iproc_i2c, TIM_CFG_OFFSET, val);
-
- bcm_iproc_i2c_enable_disable(iproc_i2c, true);
-
- return 0;
-}
-
static const struct dev_pm_ops bcm_iproc_i2c_pm_ops = {
.suspend_late = &bcm_iproc_i2c_suspend,
.resume_early = &bcm_iproc_i2c_resume
--
2.31.1