Re: [PATCH v12 4/6] i2c: tegra: Add HS mode support

[Jon Hunter <jonathanh@nvidia.com>]

On 15/11/2025 04:26, Akhil R wrote:
> Add support for HS (High Speed) mode transfers, which is supported by
> Tegra194 onwards. Also adjust the bus frequency such that it uses the
> fast plus mode when HS mode is not supported.
> 
> Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
> Signed-off-by: Kartik Rajput <kkartik@nvidia.com>
> ---
> v10 -> v12:
> 	* Update bus_freq_hz to max supported freq and updates to
> 	  accomodate the changes from Patch 2/6.
> v10 -> v11:
> 	* Update the if condition as per the comments received on:
> 	  https://lore.kernel.org/linux-tegra/20251110080502.865953-1-kkartik@nvidia.com/T/#t
> v9 -> v10:
>          * Change switch block to an if-else block.
> v5 -> v9:
>          * In the switch block, handle the case when hs mode is not
>            supported. Also update it to use Fast mode for master code
>            byte as per the I2C spec for HS mode.
> v3 -> v5:
>          * Set has_hs_mode_support to false for unsupported SoCs.
> v2 -> v3:
>          * Document tlow_hs_mode and thigh_hs_mode.
> v1 -> v2:
>          * Document has_hs_mode_support.
>          * Add a check to set the frequency to fastmode+ if the device
>            does not support HS mode but the requested frequency is more
>            than fastmode+.
> ---
>   drivers/i2c/busses/i2c-tegra.c | 59 ++++++++++++++++++++++++++++++++--
>   1 file changed, 57 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 8a696c88882e..9ebeb6a2eaf5 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -91,6 +91,7 @@
>   #define I2C_HEADER_IE_ENABLE			BIT(17)
>   #define I2C_HEADER_REPEAT_START			BIT(16)
>   #define I2C_HEADER_CONTINUE_XFER		BIT(15)
> +#define I2C_HEADER_HS_MODE			BIT(22)

This should be ordered according to the value. So place this above 
I2C_HEADER_CONT_ON_NAK.

>   #define I2C_HEADER_SLAVE_ADDR_SHIFT		1
>   
>   #define I2C_BUS_CLEAR_CNFG			0x084
> @@ -200,6 +201,8 @@ enum msg_end_type {
>    * @thigh_fast_mode: High period of the clock in fast mode.
>    * @tlow_fastplus_mode: Low period of the clock in fast-plus mode.
>    * @thigh_fastplus_mode: High period of the clock in fast-plus mode.
> + * @tlow_hs_mode: Low period of the clock in HS mode.
> + * @thigh_hs_mode: High period of the clock in HS mode.
>    * @setup_hold_time_std_mode: Setup and hold time for start and stop conditions
>    *		in standard mode.
>    * @setup_hold_time_fast_mode: Setup and hold time for start and stop
> @@ -210,6 +213,7 @@ enum msg_end_type {
>    *		in HS mode.
>    * @has_interface_timing_reg: Has interface timing register to program the tuned
>    *		timing settings.
> + * @has_hs_mode_support: Has support for high speed (HS) mode transfers.
>    */
>   struct tegra_i2c_hw_feature {
>   	bool has_continue_xfer_support;
> @@ -232,11 +236,14 @@ struct tegra_i2c_hw_feature {
>   	u32 thigh_fast_mode;
>   	u32 tlow_fastplus_mode;
>   	u32 thigh_fastplus_mode;
> +	u32 tlow_hs_mode;
> +	u32 thigh_hs_mode;
>   	u32 setup_hold_time_std_mode;
>   	u32 setup_hold_time_fast_mode;
>   	u32 setup_hold_time_fastplus_mode;
>   	u32 setup_hold_time_hs_mode;
>   	bool has_interface_timing_reg;
> +	bool has_hs_mode_support;
>   };
>   
>   /**
> @@ -646,6 +653,7 @@ static int tegra_i2c_master_reset(struct tegra_i2c_dev *i2c_dev)
>   static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
>   {
>   	u32 val, clk_divisor, clk_multiplier, tsu_thd, tlow, thigh, non_hs_mode;
> +	u32 max_bus_freq_hz;
>   	struct i2c_timings *t = &i2c_dev->timings;
>   	int err;
>   
> @@ -684,6 +692,14 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
>   	if (IS_VI(i2c_dev))
>   		tegra_i2c_vi_init(i2c_dev);
>   
> +	if (i2c_dev->hw->has_hs_mode_support)
> +		max_bus_freq_hz = I2C_MAX_HIGH_SPEED_MODE_FREQ;
> +	else
> +		max_bus_freq_hz = I2C_MAX_FAST_MODE_PLUS_FREQ;
> +
> +	if (WARN_ON(t->bus_freq_hz > max_bus_freq_hz))
> +		t->bus_freq_hz = max_bus_freq_hz;
> +
>   	if (t->bus_freq_hz <= I2C_MAX_STANDARD_MODE_FREQ) {
>   		tlow = i2c_dev->hw->tlow_std_mode;
>   		thigh = i2c_dev->hw->thigh_std_mode;
> @@ -694,11 +710,22 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
>   		thigh = i2c_dev->hw->thigh_fast_mode;
>   		tsu_thd = i2c_dev->hw->setup_hold_time_fast_mode;
>   		non_hs_mode = i2c_dev->hw->clk_divisor_fast_mode;
> -	} else {
> +	} else if (t->bus_freq_hz <= I2C_MAX_FAST_MODE_PLUS_FREQ) {
>   		tlow = i2c_dev->hw->tlow_fastplus_mode;
>   		thigh = i2c_dev->hw->thigh_fastplus_mode;
>   		tsu_thd = i2c_dev->hw->setup_hold_time_fastplus_mode;
>   		non_hs_mode = i2c_dev->hw->clk_divisor_fast_plus_mode;
> +	} else {
> +		/*
> +		 * When using HS mode, i.e. when the bus frequency is greater than fast plus mode,
> +		 * the non-hs timing registers will be used for sending the master code byte for
> +		 * transition to HS mode. Configure the non-hs timing registers for Fast Mode to
> +		 * send the master code byte at 400kHz.
> +		 */
> +		tlow = i2c_dev->hw->tlow_fast_mode;
> +		thigh = i2c_dev->hw->thigh_fast_mode;
> +		tsu_thd = i2c_dev->hw->setup_hold_time_fast_mode;
> +		non_hs_mode = i2c_dev->hw->clk_divisor_fast_mode;
>   	}
>   
>   	/* make sure clock divisor programmed correctly */
> @@ -720,6 +747,18 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
>   	if (i2c_dev->hw->has_interface_timing_reg && tsu_thd)
>   		i2c_writel(i2c_dev, tsu_thd, I2C_INTERFACE_TIMING_1);
>   
> +	/* Write HS mode registers. These will get used only for HS mode*/
> +	if (i2c_dev->hw->has_hs_mode_support) {
> +		tlow = i2c_dev->hw->tlow_hs_mode;
> +		thigh = i2c_dev->hw->thigh_hs_mode;
> +		tsu_thd = i2c_dev->hw->setup_hold_time_hs_mode;
> +
> +		val = FIELD_PREP(I2C_HS_INTERFACE_TIMING_THIGH, thigh) |
> +			FIELD_PREP(I2C_HS_INTERFACE_TIMING_TLOW, tlow);
> +		i2c_writel(i2c_dev, val, I2C_HS_INTERFACE_TIMING_0);
> +		i2c_writel(i2c_dev, tsu_thd, I2C_HS_INTERFACE_TIMING_1);
> +	}
> +
>   	clk_multiplier = (tlow + thigh + 2) * (non_hs_mode + 1);
>   
>   	err = clk_set_rate(i2c_dev->div_clk,
> @@ -1217,6 +1256,9 @@ static void tegra_i2c_push_packet_header(struct tegra_i2c_dev *i2c_dev,
>   	if (msg->flags & I2C_M_RD)
>   		packet_header |= I2C_HEADER_READ;
>   
> +	if (i2c_dev->timings.bus_freq_hz > I2C_MAX_FAST_MODE_PLUS_FREQ)
> +		packet_header |= I2C_HEADER_HS_MODE;
> +
>   	if (i2c_dev->dma_mode && !i2c_dev->msg_read)
>   		*dma_buf++ = packet_header;
>   	else
> @@ -1508,6 +1550,7 @@ static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
>   	.setup_hold_time_fastplus_mode = 0x0,
>   	.setup_hold_time_hs_mode = 0x0,
>   	.has_interface_timing_reg = false,
> +	.has_hs_mode_support = false,
>   };
>   
>   static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
> @@ -1536,6 +1579,7 @@ static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
>   	.setup_hold_time_fastplus_mode = 0x0,
>   	.setup_hold_time_hs_mode = 0x0,
>   	.has_interface_timing_reg = false,
> +	.has_hs_mode_support = false,
>   };
>   
>   static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
> @@ -1564,6 +1608,7 @@ static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
>   	.setup_hold_time_fastplus_mode = 0x0,
>   	.setup_hold_time_hs_mode = 0x0,
>   	.has_interface_timing_reg = false,
> +	.has_hs_mode_support = false,
>   };
>   
>   static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
> @@ -1592,6 +1637,7 @@ static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
>   	.setup_hold_time_fastplus_mode = 0x0,
>   	.setup_hold_time_hs_mode = 0x0,
>   	.has_interface_timing_reg = true,
> +	.has_hs_mode_support = false,
>   };
>   
>   static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
> @@ -1620,6 +1666,7 @@ static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
>   	.setup_hold_time_fastplus_mode = 0,
>   	.setup_hold_time_hs_mode = 0,
>   	.has_interface_timing_reg = true,
> +	.has_hs_mode_support = false,
>   };
>   
>   static const struct tegra_i2c_hw_feature tegra186_i2c_hw = {
> @@ -1648,6 +1695,7 @@ static const struct tegra_i2c_hw_feature tegra186_i2c_hw = {
>   	.setup_hold_time_fastplus_mode = 0,
>   	.setup_hold_time_hs_mode = 0,
>   	.has_interface_timing_reg = true,
> +	.has_hs_mode_support = false,
>   };
>   
>   static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
> @@ -1671,16 +1719,19 @@ static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
>   	.thigh_fast_mode = 0x2,
>   	.tlow_fastplus_mode = 0x2,
>   	.thigh_fastplus_mode = 0x2,
> +	.tlow_hs_mode = 0x8,
> +	.thigh_hs_mode = 0x3,
>   	.setup_hold_time_std_mode = 0x08080808,
>   	.setup_hold_time_fast_mode = 0x02020202,
>   	.setup_hold_time_fastplus_mode = 0x02020202,
>   	.setup_hold_time_hs_mode = 0x090909,
>   	.has_interface_timing_reg = true,
> +	.has_hs_mode_support = true,
>   };
>   static const struct tegra_i2c_hw_feature tegra256_i2c_hw = {
>   	.has_continue_xfer_support = true,
>   	.has_per_pkt_xfer_complete_irq = true,
> -	.clk_divisor_hs_mode = 7,
> +	.clk_divisor_hs_mode = 9,
>   	.clk_divisor_std_mode = 0x7a,
>   	.clk_divisor_fast_mode = 0x40,
>   	.clk_divisor_fast_plus_mode = 0x14,
> @@ -1698,10 +1749,14 @@ static const struct tegra_i2c_hw_feature tegra256_i2c_hw = {
>   	.thigh_fast_mode = 0x2,
>   	.tlow_fastplus_mode = 0x4,
>   	.thigh_fastplus_mode = 0x4,
> +	.tlow_hs_mode = 0x3,
> +	.thigh_hs_mode = 0x2,
>   	.setup_hold_time_std_mode = 0x08080808,
>   	.setup_hold_time_fast_mode = 0x04010101,
>   	.setup_hold_time_fastplus_mode = 0x04020202,
> +	.setup_hold_time_hs_mode = 0x030303,
>   	.has_interface_timing_reg = true,
> +	.has_hs_mode_support = true,
>   };
>   
>   static const struct of_device_id tegra_i2c_of_match[] = {

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