On 5/30/2021 3:56 PM, Chris Packham wrote:

move this up one line (to be consistent with existing bit order)

M_BB_CTRL_CLK_IN_SHIFT, ket is to have '_SHIFT' to be consistent with
existing code

+#define M_BB_SMBCLK_OUT_EN           30

M_BB_CTRL_CLK_OUT_SHIFT

+#define M_BB_SMBDAT_IN               29

M_BB_CTRL_DATA_IN_SHIFT

+#define M_BB_SMBDAT_OUT_EN           28

M_BB_CTRL_DATA_OUT_SHIFT

This puts the controller in reset and hold it there, but never brings
the controller out of reset (bcm_iproc_i2c_init called in unprepare
brings the controller out of reset)

Calling it a "reset" function is a bit misleading to me. My expectation
of a reset function is that you generate a reset pulse, ie.g., reset ->
delay -> out of reset.

Why don't you simply put this seuquence of code in the prepare_recovery
function below, instead of calling this a reset function?

+
+}
+
+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);
+
+	bcm_iproc_i2c_reset(iproc_i2c);
+
+	/* 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);

add usleep_range(100, 200) here, required delay after switching to bit
bang based on spec.

+}
+
+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);
+	udelay(100);
+
+	bcm_iproc_i2c_init(iproc_i2c);

Add sequence to re-configure to desired bus speed here after the reset
sequence (someone else in our team tested this is required to resume to
proper bus speed).

+	bcm_iproc_i2c_enable_disable(iproc_i2c, true);
+
+	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));
+}
+
+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);
+	else
+		tmp &= ~BIT(M_BB_SMBCLK_OUT_EN);
+
+	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);
+	else
+		tmp &= ~BIT(M_BB_SMBDAT_OUT_EN);
+
+	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));
+}
+
+static struct i2c_bus_recovery_info bcm_iproc_recovery_info = {

static const struct ...

'i2c_recover_bus' should not be ALWAYS called here. You don't know if
bus is actually locked up or it's other issues that caused this.

We need a logic to detect and confirm the lock up condition before
committing to recover operation:

/* 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);
	}
}

'iproc_i2c_lockup_recover' should be called in two locations in the driver:

1. After 'transaction timed out' (and after flush both TX/RX FIFOS)
2. After 'bcm_iproc_i2c_check_status' failures (and after flush both
TX/RX FIFOs).

Thanks,

Ray