Linux I2C development
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From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
To: Loic Poulain <loic.poulain@oss.qualcomm.com>,
	Robert Foss <rfoss@kernel.org>,
	Andi Shyti <andi.shyti@kernel.org>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>,
	Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>,
	Luca Weiss <luca@lucaweiss.eu>
Cc: linux-i2c@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	linux-kernel@vger.kernel.org, vladimir.zapolskiy@linaro.org,
	konradybcio@kernel.org, stephan.gerhold@linaro.org,
	Wenmeng Liu <wenmeng.liu@oss.qualcomm.com>
Subject: Re: [PATCH v3 1/5] i2c: qcom-cci: Switch msm8953 to the CCI v2 timing/rate config
Date: Fri, 31 Jul 2026 16:06:19 +0200	[thread overview]
Message-ID: <016603e6-8e87-47d7-96fb-5441ddbaeb28@oss.qualcomm.com> (raw)
In-Reply-To: <20260729-cci-clk-fix-v3-1-f3c731d1596e@oss.qualcomm.com>

On 7/29/26 2:25 PM, Loic Poulain wrote:
> The msm8953 CCI timing table is internally inconsistent. Its Standard
> and Fast timings match v1/v1.5, which are calibrated for a 19.2 MHz CCI
> clock, but its Fast+ timings are essentially the v2 values, which are
> calibrated for 37.5 MHz. Since all masters share a single CCI clock,
> no single rate can satisfy all three modes with the current table, and
> the DT assigns 19.2 MHz, so Fast+ timings are wrong.
> 
> The msm8953 CCI is the same hardware version as msm8996/sdm630, which
> already use the cci_v2_data config (37.5 MHz). 37.5 MHz is supported by
> the msm8953 CCI RCG, so reuse cci_v2_data for msm8953 as well and drop
> the redundant, inconsistent standalone table. This makes all three I2C
> modes self-consistent under a single clock rate.
> 
> Note this requires the CCI clock to run at 37.5 MHz, the driver selects
> and enforces the proper rate in following patches.
> 
> Tested-by: Wenmeng Liu <wenmeng.liu@oss.qualcomm.com>

Wenmeng, have you actually tested this on MSM8953 device?

Konrad

  reply	other threads:[~2026-07-31 14:07 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-29 12:25 [PATCH v3 0/5] i2c: qcom-cci: Enforce the required CCI clock rate Loic Poulain
2026-07-29 12:25 ` [PATCH v3 1/5] i2c: qcom-cci: Switch msm8953 to the CCI v2 timing/rate config Loic Poulain
2026-07-31 14:06   ` Konrad Dybcio [this message]
2026-07-31 14:25     ` Loic Poulain
2026-08-03  2:28     ` Wenmeng Liu
2026-07-29 12:25 ` [PATCH v3 2/5] i2c: qcom-cci: Support per-mode CCI clock rates Loic Poulain
2026-07-29 12:25 ` [PATCH v3 3/5] i2c: qcom-cci: Add 19.2 MHz timings for the v2 CCI Loic Poulain
2026-07-29 12:25 ` [PATCH v3 4/5] i2c: qcom-cci: Share the timing table across CCI revisions Loic Poulain
2026-07-29 12:25 ` [PATCH v3 5/5] i2c: qcom-cci: Enforce the required CCI clock rate Loic Poulain
2026-07-31 20:55   ` Andi Shyti
2026-08-01  7:14     ` Loic Poulain
2026-07-31 20:54 ` [PATCH v3 0/5] " Andi Shyti

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