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Wed, 21 Oct 2026 03:50:09 -0700 (PDT) X-Received: by 2002:a05:620a:480a:b0:93a:ec4:e5f2 with SMTP id af79cd13be357-93f57f87853mr411693285a.6.1792579809294; Wed, 21 Oct 2026 03:50:09 -0700 (PDT) Received: from [192.168.226.26] ([178.235.128.140]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6b403155331sm740891a12.31.2026.10.21.03.50.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 Oct 2026 03:50:08 -0700 (PDT) Message-ID: <56569e6c-bb8a-40cf-87e0-bcdee5fdc969@oss.qualcomm.com> Date: Wed, 21 Oct 2026 12:50:06 +0200 X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 5/7] i2c: qcom-cci: Extend i2c read limits based on CCI revision To: Loic Poulain , Robert Foss , Andi Shyti Cc: linux-i2c@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20261016-cci-imp-v3-0-5ee7ec1ea1a1@oss.qualcomm.com> <20261016-cci-imp-v3-5-5ee7ec1ea1a1@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <20261016-cci-imp-v3-5-5ee7ec1ea1a1@oss.qualcomm.com> Content-Type: text/plain; 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Depending on the > CCI version, the maximum read size is either 14 bytes (16 - 2) or > 254 bytes (256 - 2), corresponding to FIFO_SIZE - 2. Two FIFO > bytes are reserved by the hardware, with the first and last bytes > used for metadata such as slave ID/address reporting. > > Add CCI_I2C_READ_MAX_LEN macro to derive max_read_len from each > revision's FIFO size instead of hardcoding it and adjust the > values according the hardware revisions. > > Improve the FIFO read procedure, read the first word, discard > its ID-echo byte, then drain the remaining words in a plain loop. > Switch to readl_relaxed() for the FIFO reads, since the preceding > wait_for_completion_timeout() already orders them against the > hardware's completion interrupt. > > Signed-off-by: Loic Poulain > --- Reviewed-by: Konrad Dybcio Konrad