linux-kernel - Re: [PATCH v13 4/6] i2c: tegra: Add HS mode support

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Message-ID: <oojxbkgsa7wxbc5kglyfsmkee6ubtk3h23kwb3lwnj5sni5ys7@3cuvtx2afhi4>
Date: Thu, 27 Nov 2025 10:34:27 +0100
From: Thierry Reding <thierry.reding@...il.com>
To: Akhil R <akhilrajeev@...dia.com>
Cc: andi.shyti@...nel.org, digetx@...il.com, jonathanh@...dia.com, 
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org, 
	wsa+renesas@...g-engineering.com, wsa@...nel.org, kkartik@...dia.com, ldewangan@...dia.com, 
	smangipudi@...dia.com
Subject: Re: [PATCH v13 4/6] i2c: tegra: Add HS mode support

On Tue, Nov 18, 2025 at 07:36:18PM +0530, 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
[...]
> @@ -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,

Technically you don't need to initialize these to false, since all the
fields will be initialized to 0 by default, but it also doesn't hurt and
in this case I actually prefer the explicitness:

Acked-by: Thierry Reding <treding@...dia.com>

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