Description

In the Linux kernel, the following vulnerability has been resolved: scsi: ufs: ufs-qcom: Fix UFS OCP issue during UFS power down (PC=3) According to UFS specifications, the power-off sequence for a UFS device includes: - Sending an SSU command with Power_Condition=3 and await a response. - Asserting RST_N low. - Turning off REF_CLK. - Turning off VCC. - Turning off VCCQ/VCCQ2. As part of ufs shutdown, after the SSU command completion, asserting hardware reset (HWRST) triggers the device firmware to wake up and execute its reset routine. This routine initializes hardware blocks and takes a few milliseconds to complete. During this time, the ICCQ draws a large current. This large ICCQ current may cause issues for the regulator which is supplying power to UFS, because the turn off request from UFS driver to the regulator framework will be immediately followed by low power mode(LPM) request by regulator framework. This is done by framework because UFS which is the only client is requesting for disable. So if the rail is still in the process of shutting down while ICCQ exceeds LPM current thresholds, and LPM mode is activated in hardware during this state, it may trigger an overcurrent protection (OCP) fault in the regulator. To prevent this, a 10ms delay is added after asserting HWRST. This allows the reset operation to complete while power rails remain active and in high-power mode. Currently there is no way for Host to query whether the reset is completed or not and hence this the delay is based on experiments with Qualcomm UFS controllers across multiple UFS vendors.

References 2

• git.kernel.org https://git.kernel.org/stable/c/5127be409c6c3815c4a7d8f6d88043e44f9b9543
• git.kernel.org https://git.kernel.org/stable/c/b712f234a74c1f5ce70b5d7aec3fc2499c258141

Remediation