[PATCH v3 00/12] scsi: ufs: Add TX Equalization support for UFS 5.0
Can Guo
can.guo at oss.qualcomm.com
Sun Mar 8 08:13:57 PDT 2026
Hi,
The UFS v5.0 and UFSHCI v5.0 standards have published, introducing support
for HS-G6 (23.2 Gbps per lane) through the new UniPro V3.0 interconnect
layer and M-PHY V6.0 physical layer specifications. To achieve reliable
operation at these higher speeds, UniPro V3.0 introduces TX Equalization
and Pre-Coding mechanisms that are essential for signal integrity.
This patch series implements TX Equalization support in the UFS core
driver as specified in UFSHCI v5.0, along with the necessary vendor
operations and a reference implementation for Qualcomm UFS host
controllers.
Background
==========
TX Equalization is a signal conditioning technique that compensates for
channel impairments at high data rates (HS-G4 through HS-G6). It works
by adjusting two key parameters:
- PreShoot: Pre-emphasis applied before the main signal transition
- DeEmphasis: De-emphasis applied after the main signal transition
UniPro V3.0 defines TX Equalization Training (EQTR) procedure to
automatically discover optimal TX Equalization settings. The EQTR
procedure:
1. Starts from the most reliable link state (HS-G1)
2. Iterates through all possible PreShoot and DeEmphasis combinations
3. Evaluates signal quality using Figure of Merit (FOM) measurements
4. Selects the best settings for both host and device TX lanes
For HS-G6, Pre-Coding is also introduced to further improve signal
quality. Pre-Coding must be enabled on both transmitter and receiver
when the RX_FOM indicates it is required.
Implementation Overview
=======================
The implementation follows the UFSHCI v5.0 specification and consists of:
Core Infrastructure (Patches 1-6):
- New vops callback negotiate_pwr_mode() to allow vendors to negotiate
power mode parameters before applying TX Equalization settings
- Support for HS-G6 gear enumeration
- Complete TX EQTR procedure implementation in ufs-txeq.c
- Debugfs interface for TX Equalization parameter inspection and manual
retraining
- Module parameters for adaptive TX Equalization control
Qualcomm Implementation (Patches 7-11):
- PHY-specific configurations for TX EQTR procedure
- Vendor-specific FOM measurement support
- TX Equalization settings application
- Enable TX Equalization for HW version 0x7 and onwards
The implementation is designed to be vendor-agnostic, with platform-
specific details handled through the vops callbacks. Other vendors can
add support by implementing the three new vops:
- tx_eqtr_notify(): Called before/after TX EQTR for vendor setup
- apply_tx_eqtr_settings(): Apply vendor-specific PHY configurations
- get_rx_fom(): Retrieve vendor-specific FOM measurements if needed
Module Parameters
=================
The implementation provides several module parameters for flexibility:
- use_adaptive_txeq: Enable/disable adaptive TX Equalization (default: false)
- adaptive_txeq_gear: Minimum gear for adaptive TX EQ (default: HS-G6)
- use_txeq_presets: Use only the 8 standard presets (default: true)
- txeq_presets_selected[]: Select specific presets for EQTR
Testing
=======
This patch series has been tested on Qualcomm platforms with UFS 5.0
devices, validating:
- Successful TX EQTR completion for HS-G6
- Proper FOM evaluation and optimal settings selection
- Pre-Coding enablement for HS-G6
- Power mode changes with TX Equalization settings applied
- Report of TX Equalization settings via debugfs entries
- Report of TX EQTR histories via debug entries (see next section)
- Re-training TX Equalization via debugfs entry
Example of TX EQTR history
==========================
# cat /sys/kernel/debug/ufshcd/*ufshcd*/tx_eq_hs_gear6/device_tx_eqtr_record
Device TX EQTR record summary -
Target Power Mode: HS-G6, Rate-B
Number of records: 1
Last record timestamp: 11643252 us
TX Lane 0 FOM - PreShoot\DeEmphasis
\ 0 1 2 3 4 5 6 7
0 50 70 65 - - - - x
1 x x x x x x x x
2 100 90 70 - - - - x
3 x x x x x x x x
4 95 90 - - - - - x
5 - - - - - - - x
6 x x x x x x x x
7 x x x x x x x x
TX Lane 1 FOM - PreShoot\DeEmphasis
\ 0 1 2 3 4 5 6 7
0 50 70 60 - - - - x
1 x x x x x x x x
2 100 80 65 - - - - x
3 x x x x x x x x
4 95 85 - - - - - x
5 - - - - - - - x
6 x x x x x x x x
7 x x x x x x x x
Patch Structure
===============
Patches 1-3: Preparatory changes for power mode negotiation and HS-G6
Patch 4: Core TX Equalization and EQTR implementation
Patches 5-7: Debugfs support for TX Equalization
Patches 8-12: Qualcomm vendor implementation
Next
====
One more series has been developed to enhance TX Equalization support,
which will be submitted for review after this series is accepted:
- Provide board specific (static) TX Equalization settings from DTS
- Parse static TX Equalization settings from DTS if provided
- Apply static TX Equalization settings if use_adaptive_txeq is disabled
- Add support for UFS v5.0 attributes qTxEQGnSettings & wTxEQGnSettingsExt
- Enable persistent storage and retrieval of optimal TX Equalization settings
v2 -> v3:
1. Incorporated comments from Bart, Bean and Mani.
2. In patch 4, made ufshcd_config_pwr_mode() ignore TX EQTR error.
3. Added patch 6 to introduce helpers to pause/resume command processing.
4. In patch 7, changed debugfs entry to 'tx_eq_ctrl' and used 'refresh'
as input to trigger TX Equalization refreshing.
5. In patch 7, renamed ufshcd_retrain_tx_eq() to ufshcd_refresh_tx_eq().
6. Fixed typos and coding style issues.
v1 -> v2:
1. Incorporated Bart's comments.
2. Fixed typos and coding style issues.
3. Added enum ufshcd_pmc_policy and use enum instead of boolen parameter.
4. Updated TX Equalization debugfs entries structure.
5. Extracted ufshcd_pause/resume_command_processing() in ufshcd.c.
6. Updated sequence in Qualcomm's vops get_rx_fom() implementation.
Can Guo (12):
scsi: ufs: core: Introduce a new ufshcd vops negotiate_pwr_mode()
scsi: ufs: core: Pass force_pmc to ufshcd_config_pwr_mode() as a
parameter
scsi: ufs: core: Add UFS_HS_G6 and UFS_HS_GEAR_MAX to enum
ufs_hs_gear_tag
scsi: ufs: core: Add support for TX Equalization
scsi: ufs: core: Add debugfs entries for TX Equalization params
scsi: ufs: core: Add helpers to pause and resume command processing
scsi: ufs: core: Add support to refresh TX Equalization via debugfs
scsi: ufs: ufs-qcom: Fixup PAM-4 TX L0_L1_L2_L3 adaptation pattern
length
scsi: ufs: ufs-qcom: Implement vops tx_eqtr_notify()
scsi: ufs: ufs-qcom: Implement vops get_rx_fom()
scsi: ufs: ufs-qcom: Implement vops apply_tx_eqtr_settings()
scsi: ufs: ufs-qcom: Enable TX Equalization
drivers/ufs/core/Makefile | 2 +-
drivers/ufs/core/ufs-debugfs.c | 272 ++++++
drivers/ufs/core/ufs-txeq.c | 1288 ++++++++++++++++++++++++++++
drivers/ufs/core/ufshcd-priv.h | 57 +-
drivers/ufs/core/ufshcd.c | 187 +++-
drivers/ufs/host/ufs-amd-versal2.c | 13 +-
drivers/ufs/host/ufs-exynos.c | 44 +-
drivers/ufs/host/ufs-hisi.c | 32 +-
drivers/ufs/host/ufs-mediatek.c | 46 +-
drivers/ufs/host/ufs-qcom.c | 602 ++++++++++++-
drivers/ufs/host/ufs-qcom.h | 44 +
drivers/ufs/host/ufs-sprd.c | 13 +-
drivers/ufs/host/ufshcd-pci.c | 17 +-
include/ufs/ufshcd.h | 145 +++-
include/ufs/unipro.h | 141 ++-
15 files changed, 2788 insertions(+), 115 deletions(-)
create mode 100644 drivers/ufs/core/ufs-txeq.c
--
2.34.1
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