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[103.229.18.19]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-13e7273cd9esm749553c88.13.2026.07.28.10.45.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2026 10:45:38 -0700 (PDT) From: Anvesh Jain P Date: Tue, 28 Jul 2026 23:14:34 +0530 Subject: [PATCH 6/8] platform: arm64: qcom-hamoa-ec: Retry I2C transfers on NACK Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260728-ec_add_more_commands-v1-6-771abd65ee1a@oss.qualcomm.com> References: <20260728-ec_add_more_commands-v1-0-771abd65ee1a@oss.qualcomm.com> In-Reply-To: <20260728-ec_add_more_commands-v1-0-771abd65ee1a@oss.qualcomm.com> To: Anvesh Jain P , Sibi Sankar , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Hans de Goede , =?utf-8?q?Ilpo_J=C3=A4rvinen?= , Bryan O'Donoghue , Bjorn Andersson , Konrad Dybcio Cc: linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, platform-driver-x86@vger.kernel.org X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1785260700; l=3402; i=anvesh.p@oss.qualcomm.com; s=20260313; h=from:subject:message-id; bh=t44lY22s35NEeNaqS+Z3V6CASIdAbd2ynB7Wy9hB8i8=; b=MrRZiNl4voVXf4hRnRJ8F06/N2JEkPvmDNWY02iNeBScF/2lUgP9On8XD/rF/dtSeM7/rxlvK zTzwWjST1EdAhEws4JCuWMw9je5aUF7DCplWvhyRimq8CYaZsnOoWp0 X-Developer-Key: i=anvesh.p@oss.qualcomm.com; a=ed25519; pk=8o9EG7gkPe2Er9y9UVCx8MTdcFCwU8Pa54hBZPuduXE= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzI4MDE1NiBTYWx0ZWRfX5q3hxPUVZ1di Vk0oO9nlXMk6e5ztxc8t4ilrKARgS6pjg3XOv+n9+TzwwGg0zOWThC4bWG+LsXFSN+JMntuKxip VyiqppZDmiy9aNMujHDZzQP0dD8dBmpl/P3KCuOYpUOklSMtaI1/xsImhn64THOTH2jByMvG2Tr GDisbSO9SRCioFu+jV+xff6y4OVB9ElcEkstUSCl3wQYmxwcSiTp+Lx1+hsGo/JHUI2mpLsin0H 1Jz3ldVdSYi9AxbEY9Obu24+whoM4fAt9coSvATyp0IBuTYAQEPDiWrIAEc9Be5xv52ZfVCb3wq AMR1NRjrNBpmGDAqjcZEAy3Gj2Eff4tjOEDG6ss6NpUcLuT6IujyMWGY52HBznTXfGErCLWuJUe 0J3PQdZOSieKHFJe/0BwJCfLw0yG4+KHFFdS8r1jMTKu/a6+49f77mUC0xcpvF0hUgmoajw27wf W0OI1xe4FOUDWRvKQZg== X-Proofpoint-ORIG-GUID: qnUr8_dPoxxCGys2sWzIqDVQHbY-Rfc9 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzI4MDE1NiBTYWx0ZWRfX17MZCZjBmwix mgGvBkxxNDLsXX65Rnl+dFvmWaaLtorrLkm/HcvsyX9cy7MJdH/zSWL58uUr8ehZP0fwo/dopHL 9dWtpfw31VZikTyaqI9YSzRwvwf8ZdY= X-Authority-Analysis: v=2.4 cv=VezH+lp9 c=1 sm=1 tr=0 ts=6a68eac4 cx=c_pps a=Oh5Dbbf/trHjhBongsHeRQ==:117 a=Ou0eQOY4+eZoSc0qltEV5Q==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=DJpcGTmdVt4CTyJn9g5Z:22 a=EUspDBNiAAAA:8 a=PsJaXn4vnLjY93LmvYYA:9 a=QEXdDO2ut3YA:10 a=_Vgx9l1VpLgwpw_dHYaR:22 X-Proofpoint-GUID: qnUr8_dPoxxCGys2sWzIqDVQHbY-Rfc9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-28_04,2026-07-28_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 clxscore=1015 malwarescore=0 suspectscore=0 bulkscore=0 spamscore=0 lowpriorityscore=0 phishscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607280156 The EC firmware NACKs the bus instead of clock-stretching while it is busy servicing internal work (e.g. right after boot, when it is also emitting a burst of SCI events). A transfer issued in that window fails with -ENXIO even though the EC is otherwise healthy. This isn't visible with the smbus-only command set used previously; it surfaced while stress-testing the new fan LUT command on Hamoa, which issues raw i2c_transfer() calls more aggressively and is thus more likely to land in the NACK window right after boot or during an SCI event burst. Retry qcom_ec_write() and qcom_ec_read() a bounded number of times with a short delay when the EC NACKs the transfer, before giving up. Signed-off-by: Anvesh Jain P --- drivers/platform/arm64/qcom-hamoa-ec.c | 40 +++++++++++++++++++++++++++++----- 1 file changed, 34 insertions(+), 6 deletions(-) diff --git a/drivers/platform/arm64/qcom-hamoa-ec.c b/drivers/platform/arm64/qcom-hamoa-ec.c index a420a180a194..122ae27c2b48 100644 --- a/drivers/platform/arm64/qcom-hamoa-ec.c +++ b/drivers/platform/arm64/qcom-hamoa-ec.c @@ -64,6 +64,18 @@ #define EC_SOC_TJ_TEMP_POLL_JIFFIES msecs_to_jiffies(125) +/* + * The EC firmware NACKs the bus instead of clock-stretching while it is + * busy servicing internal work (e.g. right after boot, when it is also + * emitting a burst of SCI events). This NACK only occurs at the address + * phase, so retrying the whole transfer is safe. Attempt the transfer a + * bounded number of times on NACK before giving up; a genuinely missing + * or unpowered device pays a worst-case added latency of + * (EC_I2C_NACK_MAX_ATTEMPTS - 1) * EC_I2C_NACK_RETRY_DELAY_MS. + */ +#define EC_I2C_NACK_MAX_ATTEMPTS 5 +#define EC_I2C_NACK_RETRY_DELAY_MS 20 + enum qcom_ec_sci_events { EC_FAN1_STATUS_CHANGE_EVT = 0x30, EC_FAN2_STATUS_CHANGE_EVT, @@ -233,11 +245,20 @@ static int qcom_ec_write(struct qcom_ec *ec, u8 cmd, const u8 *data, size_t len) msg.buf[0] = cmd; memcpy(&msg.buf[1], data, len); - ret = i2c_transfer(ec->client->adapter, &msg, 1); + for (int i = 0; i < EC_I2C_NACK_MAX_ATTEMPTS; i++) { + ret = i2c_transfer(ec->client->adapter, &msg, 1); + ret = ret == 1 ? 0 : (ret < 0 ? ret : -EIO); + if (ret != -ENXIO || i == EC_I2C_NACK_MAX_ATTEMPTS - 1) + break; + + dev_dbg(&ec->client->dev, + "EC busy (NACK), retrying write of cmd 0x%02x\n", cmd); + msleep(EC_I2C_NACK_RETRY_DELAY_MS); + } kfree(msg.buf); - return ret == 1 ? 0 : (ret < 0 ? ret : -EIO); + return ret; } static int qcom_ec_read(struct qcom_ec *ec, u8 cmd, const u8 *subcmd, @@ -281,11 +302,18 @@ static int qcom_ec_read(struct qcom_ec *ec, u8 cmd, const u8 *subcmd, msgs[1].len = resp_len; msgs[1].buf = read_buf; - ret = i2c_transfer(client->adapter, msgs, 2); - if (ret != 2) { - ret = ret < 0 ? ret : -EIO; - goto out; + for (int i = 0; i < EC_I2C_NACK_MAX_ATTEMPTS; i++) { + ret = i2c_transfer(client->adapter, msgs, 2); + ret = ret == 2 ? 0 : (ret < 0 ? ret : -EIO); + if (ret != -ENXIO || i == EC_I2C_NACK_MAX_ATTEMPTS - 1) + break; + + dev_dbg(&client->dev, + "EC busy (NACK), retrying read of cmd 0x%02x\n", cmd); + msleep(EC_I2C_NACK_RETRY_DELAY_MS); } + if (ret) + goto out; if (read_buf[0] == 0 || read_buf[0] == 0xff) { ret = -EOPNOTSUPP; -- 2.34.1