[PATCH v8 30/32] i2c: tegra: Clean up and improve comments

Dmitry Osipenko
2020-09-22T22:53:33Z

Make all comments to be consistent in regards to capitalization and
punctuation, correct spelling and grammar errors, improve wording.

Reviewed-by: Thierry Reding <treding@nvidia.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/i2c/busses/i2c-tegra.c | 88 ++++++++++++++++++----------------
1 file changed, 47 insertions(+), 41 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 6cbcad366b62..ebbfd7ed11c0 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -136,7 +136,7 @@
/* configuration load timeout in microseconds */
#define I2C_CONFIG_LOAD_TIMEOUT 1000000

-/* Packet header size in bytes */
+/* packet header size in bytes */
#define I2C_PACKET_HEADER_SIZE 12

/*
@@ -148,11 +148,10 @@
#define I2C_PIO_MODE_PREFERRED_LEN 32

/*
- * msg_end_type: The bus control which need to be send at end of transfer.
- * @MSG_END_STOP: Send stop pulse at end of transfer.
- * @MSG_END_REPEAT_START: Send repeat start at end of transfer.
- * @MSG_END_CONTINUE: The following on message is coming and so do not send
- * stop or repeat start.
+ * msg_end_type: The bus control which needs to be sent at end of transfer.
+ * @MSG_END_STOP: Send stop pulse.
+ * @MSG_END_REPEAT_START: Send repeat-start.
+ * @MSG_END_CONTINUE: Don't send stop or repeat-start.
*/
enum msg_end_type {
MSG_END_STOP,
@@ -161,10 +160,10 @@ enum msg_end_type {
};

/**
- * struct tegra_i2c_hw_feature : Different HW support on Tegra
- * @has_continue_xfer_support: Continue transfer supports.
+ * struct tegra_i2c_hw_feature : per hardware generation features
+ * @has_continue_xfer_support: continue-transfer supported
* @has_per_pkt_xfer_complete_irq: Has enable/disable capability for transfer
- * complete interrupt per packet basis.
+ * completion interrupt on per packet basis.
* @has_config_load_reg: Has the config load register to load the new
* configuration.
* @clk_divisor_hs_mode: Clock divisor in HS mode.
@@ -184,7 +183,7 @@ enum msg_end_type {
* @has_mst_fifo: The I2C controller contains the new MST FIFO interface that
* provides additional features and allows for longer messages to
* be transferred in one go.
- * @quirks: i2c adapter quirks for limiting write/read transfer size and not
+ * @quirks: I2C adapter quirks for limiting write/read transfer size and not
* allowing 0 length transfers.
* @supports_bus_clear: Bus Clear support to recover from bus hang during
* SDA stuck low from device for some unknown reasons.
@@ -245,7 +244,7 @@ struct tegra_i2c_hw_feature {
* @msg_err: error code for completed message
* @msg_buf: pointer to current message data
* @msg_buf_remaining: size of unsent data in the message buffer
- * @msg_read: identifies read transfers
+ * @msg_read: indicates that the transfer is a read access
* @bus_clk_rate: current I2C bus clock rate
* @multimaster_mode: indicates that I2C controller is in multi-master mode
* @tx_dma_chan: DMA transmit channel
@@ -307,8 +306,8 @@ static u32 dvc_readl(struct tegra_i2c_dev *i2c_dev, unsigned int reg)
}

/*
- * i2c_writel and i2c_readl will offset the register if necessary to talk
- * to the I2C block inside the DVC block
+ * If necessary, i2c_writel() and i2c_readl() will offset the register
+ * in order to talk to the I2C block inside the DVC block.
*/
static u32 tegra_i2c_reg_addr(struct tegra_i2c_dev *i2c_dev, unsigned int reg)
{
@@ -323,7 +322,7 @@ static void i2c_writel(struct tegra_i2c_dev *i2c_dev, u32 val, unsigned int reg)
{
writel_relaxed(val, i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg));

- /* Read back register to make sure that register writes completed */
+ /* read back register to make sure that register writes completed */
if (reg != I2C_TX_FIFO)
readl_relaxed(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg));
}
@@ -475,7 +474,7 @@ static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
* block. This block is identical to the rest of the I2C blocks, except that
* it only supports master mode, it has registers moved around, and it needs
* some extra init to get it into I2C mode. The register moves are handled
- * by i2c_readl and i2c_writel
+ * by i2c_readl() and i2c_writel().
*/
static void tegra_dvc_init(struct tegra_i2c_dev *i2c_dev)
{
@@ -633,7 +632,7 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
break;
}

- /* Make sure clock divisor programmed correctly */
+ /* make sure clock divisor programmed correctly */
clk_divisor = FIELD_PREP(I2C_CLK_DIVISOR_HSMODE,
i2c_dev->hw->clk_divisor_hs_mode) |
FIELD_PREP(I2C_CLK_DIVISOR_STD_FAST_MODE, non_hs_mode);
@@ -646,8 +645,8 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
}

/*
- * configure setup and hold times only when tsu_thd is non-zero.
- * otherwise, preserve the chip default values
+ * Configure setup and hold times only when tsu_thd is non-zero.
+ * Otherwise, preserve the chip default values.
*/
if (i2c_dev->hw->has_interface_timing_reg && tsu_thd)
i2c_writel(i2c_dev, tsu_thd, I2C_INTERFACE_TIMING_1);
@@ -691,7 +690,7 @@ static int tegra_i2c_disable_packet_mode(struct tegra_i2c_dev *i2c_dev)

/*
* NACK interrupt is generated before the I2C controller generates
- * the STOP condition on the bus. So wait for 2 clock periods
+ * the STOP condition on the bus. So, wait for 2 clock periods
* before disabling the controller so that the STOP condition has
* been delivered properly.
*/
@@ -712,8 +711,8 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
u32 val;

/*
- * Catch overflow due to message fully sent
- * before the check for RX FIFO availability.
+ * Catch overflow due to message fully sent before the check for
+ * RX FIFO availability.
*/
if (WARN_ON_ONCE(!(i2c_dev->msg_buf_remaining)))
return -EINVAL;
@@ -726,7 +725,7 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
rx_fifo_avail = FIELD_GET(I2C_FIFO_STATUS_RX, val);
}

- /* Rounds down to not include partial word at the end of buf */
+ /* round down to exclude partial word at the end of buffer */
words_to_transfer = buf_remaining / BYTES_PER_FIFO_WORD;
if (words_to_transfer > rx_fifo_avail)
words_to_transfer = rx_fifo_avail;
@@ -738,8 +737,8 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
rx_fifo_avail -= words_to_transfer;

/*
- * If there is a partial word at the end of buf, handle it manually to
- * prevent overwriting past the end of buf
+ * If there is a partial word at the end of buffer, handle it
+ * manually to prevent overwriting past the end of buffer.
*/
if (rx_fifo_avail > 0 && buf_remaining > 0) {
/*
@@ -779,10 +778,15 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
tx_fifo_avail = FIELD_GET(I2C_FIFO_STATUS_TX, val);
}

- /* Rounds down to not include partial word at the end of buf */
+ /* round down to exclude partial word at the end of buffer */
words_to_transfer = buf_remaining / BYTES_PER_FIFO_WORD;

- /* It's very common to have < 4 bytes, so optimize that case. */
+ /*
+ * This hunk pushes 4 bytes at a time into the TX FIFO.
+ *
+ * It's very common to have < 4 bytes, hence there is no word
+ * to push if we have less than 4 bytes to transfer.
+ */
if (words_to_transfer) {
if (words_to_transfer > tx_fifo_avail)
words_to_transfer = tx_fifo_avail;
@@ -806,8 +810,8 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
}

/*
- * If there is a partial word at the end of buf, handle it manually to
- * prevent reading past the end of buf, which could cross a page
+ * If there is a partial word at the end of buffer, handle it manually
+ * to prevent reading past the end of buffer, which could cross a page
* boundary and fault.
*/
if (tx_fifo_avail > 0 && buf_remaining > 0) {
@@ -855,7 +859,7 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
}

/*
- * I2C transfer is terminated during the bus clear so skip
+ * I2C transfer is terminated during the bus clear, so skip
* processing the other interrupts.
*/
if (i2c_dev->hw->supports_bus_clear && (status & I2C_INT_BUS_CLR_DONE))
@@ -891,7 +895,8 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
* During message read XFER_COMPLETE interrupt is triggered prior to
* DMA completion and during message write XFER_COMPLETE interrupt is
* triggered after DMA completion.
- * PACKETS_XFER_COMPLETE indicates completion of all bytes of transfer.
+ *
+ * PACKETS_XFER_COMPLETE indicates completion of all bytes of transfer,
* so forcing msg_buf_remaining to 0 in DMA mode.
*/
if (status & I2C_INT_PACKET_XFER_COMPLETE) {
@@ -909,7 +914,7 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
}
goto done;
err:
- /* An error occurred, mask all interrupts */
+ /* mask all interrupts on error */
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);
@@ -1332,6 +1337,7 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
enum msg_end_type end_type = MSG_END_STOP;

if (i < (num - 1)) {
+ /* check whether follow up message is coming */
if (msgs[i + 1].flags & I2C_M_NOSTART)
end_type = MSG_END_CONTINUE;
else
@@ -1561,7 +1567,6 @@ static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
.has_interface_timing_reg = true,
};

-/* Match table for of_platform binding */
static const struct of_device_id tegra_i2c_of_match[] = {
{ .compatible = "nvidia,tegra194-i2c", .data = &tegra194_i2c_hw, },
{ .compatible = "nvidia,tegra186-i2c", .data = &tegra186_i2c_hw, },
@@ -1585,7 +1590,7 @@ static void tegra_i2c_parse_dt(struct tegra_i2c_dev *i2c_dev)
err = of_property_read_u32(np, "clock-frequency",
&i2c_dev->bus_clk_rate);
if (err)
- i2c_dev->bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ; /* default clock rate */
+ i2c_dev->bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ;

multi_mode = of_property_read_bool(np, "multi-master");
i2c_dev->multimaster_mode = multi_mode;
@@ -1718,11 +1723,13 @@ static int tegra_i2c_probe(struct platform_device *pdev)
goto release_clocks;

/*
- * VI I2C is in VE power domain which is not always on and not
- * an IRQ safe. So, IRQ safe device can't be attached to a non-IRQ
- * safe domain as it prevents powering off the PM domain.
- * Also, VI I2C device don't need to use runtime IRQ safe as it will
- * not be used for atomic transfers.
+ * VI I2C is in VE power domain which is not always ON and not
+ * IRQ-safe. Thus, IRQ-safe device shouldn't be attached to a
+ * non IRQ-safe domain because this prevents powering off the power
+ * domain.
+ *
+ * VI I2C device shouldn't be marked as IRQ-safe because VI I2C won't
+ * be used for atomic transfers.
*/
if (!i2c_dev->is_vi)
pm_runtime_irq_safe(i2c_dev->dev);
@@ -1793,9 +1800,8 @@ static int __maybe_unused tegra_i2c_runtime_resume(struct device *dev)

/*
* VI I2C device is attached to VE power domain which goes through
- * power ON/OFF during PM runtime resume/suspend. So, controller
- * should go through reset and need to re-initialize after power
- * domain ON.
+ * power ON/OFF during runtime PM resume/suspend, meaning that
+ * controller needs to be re-initialized after power ON.
*/
if (i2c_dev->is_vi) {
err = tegra_i2c_init(i2c_dev);
--
2.27.0