From 94a5573f0719cf82143d401658d0ad2940220b8d Mon Sep 17 00:00:00 2001 From: Dmitry Osipenko Date: Wed, 30 Sep 2020 01:19:13 +0300 Subject: i2c: tegra: Clean up and improve comments Make all comments to be consistent in regards to capitalization and punctuation, correct spelling and grammar errors, improve wording. Reviewed-by: Thierry Reding Reviewed-by: Andy Shevchenko Tested-by: Thierry Reding Signed-off-by: Dmitry Osipenko Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-tegra.c | 88 ++++++++++++++++++++++-------------------- 1 file changed, 47 insertions(+), 41 deletions(-) (limited to 'drivers/i2c') diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c index dbf83424fb2f..194c9ec84713 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 @@ err_out: * 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); @@ -1333,6 +1338,7 @@ 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 @@ -1562,7 +1568,6 @@ 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, }, @@ -1586,7 +1591,7 @@ 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; @@ -1719,11 +1724,13 @@ 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); @@ -1794,9 +1801,8 @@ 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); -- cgit v1.2.3