linux-kernel - Re: [PATCH 1/6] i2c: tegra: Add support for Tegra234 I2C

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Date:   Wed, 19 Jan 2022 15:20:35 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Akhil R <akhilrajeev@...dia.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Petlozu Pravareshwar <petlozup@...dia.com>
Subject: Re: [PATCH 1/6] i2c: tegra: Add support for Tegra234 I2C

19.01.2022 11:20, Akhil R пишет:
>> 13.01.2022 16:30, Akhil R пишет:
>>> +static const struct tegra_i2c_hw_feature tegra234_i2c_hw = {
>>> +     .has_continue_xfer_support = true,
>>> +     .has_per_pkt_xfer_complete_irq = true,
>>> +     .clk_divisor_hs_mode = 0x2,
>>> +     .clk_divisor_std_mode = 0x4f,
>>> +     .clk_divisor_fast_mode = 0x58,
>>> +     .clk_divisor_fast_plus_mode = 0x24,
>>> +     .has_config_load_reg = true,
>>> +     .has_multi_master_mode = true,
>>> +     .has_slcg_override_reg = true,
>>> +     .has_mst_fifo = true,
>>> +     .quirks = &tegra194_i2c_quirks,
>>> +     .supports_bus_clear = true,
>>> +     .has_apb_dma = false,
>>> +     .tlow_std_mode = 0x8,
>>> +     .thigh_std_mode = 0x7,
>>> +     .tlow_fast_fastplus_mode = 0x1,
>>> +     .thigh_fast_fastplus_mode = 0x1,
>>> +     .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, };
>>
>> Why tegra194_i2c_hw can't be reused by T234? Looks like I2C h/w hasn't
>> changed and somebody just made a minor tuning of the timing parameters, does
>> it really matter in practice?
> The timing parameters are important to get the desired data rate for I2C. The values,
> unfortunately, cannot be reused from Tegra194.

>From where those T194 parameters specified in the Tegra I2C driver came
from?

I'm now looking at T194 TRM (Xavier_TRM_DP09253002_v1.3p 10.2.3.1.1
Example Settings for Various I2C Speeds) and see that all the values
should match T234. Please check whether T194 configuration is correct
and fix it if needed.