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Message-ID: <2293baeb-cadf-4948-83ed-ec332941a958@nvidia.com>
Date: Tue, 18 Nov 2025 14:19:12 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: Akhil R <akhilrajeev@...dia.com>, andi.shyti@...nel.org,
digetx@...il.com, linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-tegra@...r.kernel.org, thierry.reding@...il.com,
wsa+renesas@...g-engineering.com, wsa@...nel.org
Cc: kkartik@...dia.com, ldewangan@...dia.com, smangipudi@...dia.com
Subject: Re: [PATCH v13 4/6] i2c: tegra: Add HS mode support
On 18/11/2025 14:06, Akhil R wrote:
> Add support for High Speed (HS) mode transfers for Tegra194 and later
> chips. While HS mode has been documented in the technical reference
> manuals since Tegra20, the hardware implementation appears to be broken
> on all chips prior to Tegra194.
>
> When HS mode is not supported, set the frequency to FM+ instead.
>
> Signed-off-by: Akhil R <akhilrajeev@...dia.com>
> Signed-off-by: Kartik Rajput <kkartik@...dia.com>
> ---
> v12 ->v13:
> * Update has_hs_mode_support to enable_hs_mode_support
> * Update the commit description
> v11 -> 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 470d0d32d571..b2fe8add895b 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -85,6 +85,7 @@
> #define PACKET_HEADER0_PROTOCOL GENMASK(7, 4)
> #define PACKET_HEADER0_PROTOCOL_I2C 1
>
> +#define I2C_HEADER_HS_MODE BIT(22)
> #define I2C_HEADER_CONT_ON_NAK BIT(21)
> #define I2C_HEADER_READ BIT(19)
> #define I2C_HEADER_10BIT_ADDR BIT(18)
> @@ -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.
> + * @enable_hs_mode_support: Enable 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 enable_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->enable_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->enable_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,
> + .enable_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,
> + .enable_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,
> + .enable_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,
> + .enable_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,
> + .enable_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,
> + .enable_hs_mode_support = false,
> };
>
> static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
> @@ -1671,17 +1719,20 @@ 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,
> + .enable_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,
> @@ -1699,10 +1750,14 @@ 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,
> + .enable_hs_mode_support = true,
> };
>
> static const struct of_device_id tegra_i2c_of_match[] = {
Reviewed-by: Jon Hunter <jonathanh@...dia.com>
Thanks!
Jon
--
nvpublic
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