Re: [PATCH v8 2/4] i2c: tegra: Add HS mode support

[Jon Hunter <jonathanh@nvidia.com>]

On 17/09/2025 09:56, Kartik Rajput wrote:
> From: Akhil R <akhilrajeev@nvidia.com>
> 
> Add support for HS (High Speed) mode transfers, which is supported by
> Tegra194 onwards.
> 
> Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
> Signed-off-by: Kartik Rajput <kkartik@nvidia.com>
> ---
> 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 | 33 +++++++++++++++++++++++++++++++++
>   1 file changed, 33 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index d908e5e3f0af..6f816de8b3af 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)
>   #define I2C_HEADER_SLAVE_ADDR_SHIFT		1
>   
>   #define I2C_BUS_CLEAR_CNFG			0x084
> @@ -198,6 +199,8 @@ enum msg_end_type {
>    * @thigh_std_mode: High period of the clock in standard mode.
>    * @tlow_fast_fastplus_mode: Low period of the clock in fast/fast-plus modes.
>    * @thigh_fast_fastplus_mode: High period of the clock in fast/fast-plus modes.
> + * @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_fast_plus_mode: Setup and hold time for start and stop
> @@ -206,6 +209,7 @@ 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;
> @@ -226,10 +230,13 @@ struct tegra_i2c_hw_feature {
>   	u32 thigh_std_mode;
>   	u32 tlow_fast_fastplus_mode;
>   	u32 thigh_fast_fastplus_mode;
> +	u32 tlow_hs_mode;
> +	u32 thigh_hs_mode;
>   	u32 setup_hold_time_std_mode;
>   	u32 setup_hold_time_fast_fast_plus_mode;
>   	u32 setup_hold_time_hs_mode;
>   	bool has_interface_timing_reg;
> +	bool has_hs_mode_support;
>   };
>   
>   /**
> @@ -717,6 +724,20 @@ 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);
> +	} else if (t->bus_freq_hz > I2C_MAX_FAST_MODE_PLUS_FREQ) {
> +		t->bus_freq_hz = I2C_MAX_FAST_MODE_PLUS_FREQ;

No mention in the changelog about this part. Looks like this is a fallback.

Should all of this be handled in the case statement for t->bus_freq_hz?

> +	}
> +
>   	clk_multiplier = (tlow + thigh + 2) * (non_hs_mode + 1);
>   
>   	err = clk_set_rate(i2c_dev->div_clk,
> @@ -1214,6 +1235,9 @@ 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
> @@ -1502,6 +1526,7 @@ static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
>   	.setup_hold_time_fast_fast_plus_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 = {
> @@ -1527,6 +1552,7 @@ static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
>   	.setup_hold_time_fast_fast_plus_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 = {
> @@ -1552,6 +1578,7 @@ static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
>   	.setup_hold_time_fast_fast_plus_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 = {
> @@ -1577,6 +1604,7 @@ static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
>   	.setup_hold_time_fast_fast_plus_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 = {
> @@ -1602,6 +1630,7 @@ static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
>   	.setup_hold_time_fast_fast_plus_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 = {
> @@ -1627,6 +1656,7 @@ static const struct tegra_i2c_hw_feature tegra186_i2c_hw = {
>   	.setup_hold_time_fast_fast_plus_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 = {
> @@ -1648,10 +1678,13 @@ static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
>   	.thigh_std_mode = 0x7,
>   	.tlow_fast_fastplus_mode = 0x2,
>   	.thigh_fast_fastplus_mode = 0x2,
> +	.tlow_hs_mode = 0x8,
> +	.thigh_hs_mode = 0x3,
>   	.setup_hold_time_std_mode = 0x08080808,
>   	.setup_hold_time_fast_fast_plus_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 = {

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