From 77821b4678f93b0b45870c04b7c06c364ed090de Mon Sep 17 00:00:00 2001 From: Shardar Shariff Md Date: Wed, 31 Aug 2016 18:58:44 +0530 Subject: [PATCH] i2c: tegra: proper handling of error cases To summarize the issue observed in error cases: SW Flow: For i2c message transfer, packet header and data payload is posted and then required error/packet completion interrupts are enabled later. HW flow: HW process the packet just after packet header is posted, if ARB lost/NACK error occurs (SW will not handle immediately when error happens as error interrupts are not enabled at this point). HW assumes error is acknowledged and clears current data in FIFO, But SW here posts the remaining data payload which still stays in FIFO as stale data (data without packet header). Now once the interrupts are enabled, SW handles ARB lost/NACK error by clearing the ARB lost/NACK interrupt. Now HW assumes that SW attended the error and will parse/process stale data (data without packet header) present in FIFO which causes invalid NACK errors. Fix: Enable the error interrupts before posting the packet into FIFO which make sure HW to not clear the fifo. Also disable the packet mode before acknowledging errors (ARB lost/NACK error) to not process any stale data. As error interrupts are enabled before posting the packet header use spinlock to avoid preempting. Signed-off-by: Shardar Shariff Md Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-tegra.c | 29 +++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-) diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c index 243753564110..c15d5755bccc 100644 --- a/drivers/i2c/busses/i2c-tegra.c +++ b/drivers/i2c/busses/i2c-tegra.c @@ -196,6 +196,7 @@ struct tegra_i2c_dev { u16 clk_divisor_non_hs_mode; bool is_suspended; bool is_multimaster_mode; + spinlock_t xfer_lock; }; static void dvc_writel(struct tegra_i2c_dev *i2c_dev, u32 val, @@ -542,14 +543,27 @@ err: return err; } +static int tegra_i2c_disable_packet_mode(struct tegra_i2c_dev *i2c_dev) +{ + u32 cnfg; + + cnfg = i2c_readl(i2c_dev, I2C_CNFG); + if (cnfg & I2C_CNFG_PACKET_MODE_EN) + i2c_writel(i2c_dev, cnfg & ~I2C_CNFG_PACKET_MODE_EN, I2C_CNFG); + + return tegra_i2c_wait_for_config_load(i2c_dev); +} + static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) { u32 status; const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST; struct tegra_i2c_dev *i2c_dev = dev_id; + unsigned long flags; status = i2c_readl(i2c_dev, I2C_INT_STATUS); + spin_lock_irqsave(&i2c_dev->xfer_lock, flags); if (status == 0) { dev_warn(i2c_dev->dev, "irq status 0 %08x %08x %08x\n", i2c_readl(i2c_dev, I2C_PACKET_TRANSFER_STATUS), @@ -565,6 +579,7 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) } if (unlikely(status & status_err)) { + tegra_i2c_disable_packet_mode(i2c_dev); if (status & I2C_INT_NO_ACK) i2c_dev->msg_err |= I2C_ERR_NO_ACK; if (status & I2C_INT_ARBITRATION_LOST) @@ -594,7 +609,7 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) BUG_ON(i2c_dev->msg_buf_remaining); complete(&i2c_dev->msg_complete); } - return IRQ_HANDLED; + goto done; err: /* An error occurred, mask all interrupts */ tegra_i2c_mask_irq(i2c_dev, I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST | @@ -605,6 +620,8 @@ err: dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS); complete(&i2c_dev->msg_complete); +done: + spin_unlock_irqrestore(&i2c_dev->xfer_lock, flags); return IRQ_HANDLED; } @@ -614,6 +631,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev, u32 packet_header; u32 int_mask; unsigned long time_left; + unsigned long flags; tegra_i2c_flush_fifos(i2c_dev); @@ -626,6 +644,11 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev, i2c_dev->msg_read = (msg->flags & I2C_M_RD); reinit_completion(&i2c_dev->msg_complete); + spin_lock_irqsave(&i2c_dev->xfer_lock, flags); + + int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST; + tegra_i2c_unmask_irq(i2c_dev, int_mask); + packet_header = (0 << PACKET_HEADER0_HEADER_SIZE_SHIFT) | PACKET_HEADER0_PROTOCOL_I2C | (i2c_dev->cont_id << PACKET_HEADER0_CONT_ID_SHIFT) | @@ -655,14 +678,15 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev, if (!(msg->flags & I2C_M_RD)) tegra_i2c_fill_tx_fifo(i2c_dev); - int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST; if (i2c_dev->hw->has_per_pkt_xfer_complete_irq) int_mask |= I2C_INT_PACKET_XFER_COMPLETE; if (msg->flags & I2C_M_RD) int_mask |= I2C_INT_RX_FIFO_DATA_REQ; else if (i2c_dev->msg_buf_remaining) int_mask |= I2C_INT_TX_FIFO_DATA_REQ; + tegra_i2c_unmask_irq(i2c_dev, int_mask); + spin_unlock_irqrestore(&i2c_dev->xfer_lock, flags); dev_dbg(i2c_dev->dev, "unmasked irq: %02x\n", i2c_readl(i2c_dev, I2C_INT_MASK)); @@ -899,6 +923,7 @@ static int tegra_i2c_probe(struct platform_device *pdev) i2c_dev->is_dvc = of_device_is_compatible(pdev->dev.of_node, "nvidia,tegra20-i2c-dvc"); init_completion(&i2c_dev->msg_complete); + spin_lock_init(&i2c_dev->xfer_lock); if (!i2c_dev->hw->has_single_clk_source) { fast_clk = devm_clk_get(&pdev->dev, "fast-clk"); -- 2.20.1