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

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Message-ID: <DM5PR12MB1850C40F3ECF34D30AEE3D83C05A9@DM5PR12MB1850.namprd12.prod.outlook.com>
Date:   Thu, 20 Jan 2022 14:23:50 +0000
From:   Akhil R <akhilrajeev@...dia.com>
To:     Dmitry Osipenko <digetx@...il.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>,
        Krishna Yarlagadda <kyarlagadda@...dia.com>
Subject: RE: [PATCH 1/6] i2c: tegra: Add support for Tegra234 I2C

> >>> +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.

Thanks for highlighting this. There are adjustments in the default timing values
of T194 from TRM. I am checking if these changes can be used for T234 as well.
Will send an updated patch if the same values apply for T234.

Thanks,
Akhil