From: Peter Wang peter.wang@mediatek.com
[ Upstream commit 15ef3f5aa822f32524cba1463422a2c9372443f0 ]
Improve the recovery process for failed resume operations. Log the device's power status and return 0 if both resume and recovery fail to prevent I/O hang.
Signed-off-by: Peter Wang peter.wang@mediatek.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
YES
Explanation - What changed (drivers/ufs/host/ufs-mediatek.c: fail path in `ufs_mtk_resume()`): - Old behavior: on resume failure, jump to `fail:` and return `ufshcd_link_recovery(hba)` (propagate error). - New behavior: at `fail:` call `ufshcd_link_recovery(hba)` and log runtime PM status if it fails; then unconditionally `return 0 /* Cannot return a failure, otherwise, the I/O will hang. */`. - Code reference: drivers/ufs/host/ufs-mediatek.c:1814 (call to `ufshcd_link_recovery(hba)`), followed by the new `dev_err()` that prints `hba->dev->power.request`, `runtime_status`, `runtime_error`, and the unconditional `return 0`.
- Why this fixes a real bug affecting users (I/O hang): - The UFS core resume path calls the vendor resume first and bails out immediately if the vops `resume()` returns an error, skipping core recovery steps like hibern8 exit or full reset/restore: - Code reference: drivers/ufs/core/ufshcd.c:10011 (`ret = ufshcd_vops_resume(hba, pm_op); if (ret) goto out;`). - If the Mediatek variant previously returned an error from `ufs_mtk_resume()`, the core code would not attempt `ufshcd_uic_hibern8_exit()` or `ufshcd_reset_and_restore()`, leaving the link/device in a bad state and causing I/O to hang. - With this patch, the Mediatek driver tries `ufshcd_link_recovery()` locally and returns 0, allowing the core resume sequence to proceed: - If the link is in Hibern8, the core performs `ufshcd_uic_hibern8_exit()` (drivers/ufs/core/ufshcd.c:10025) and sets the link active. - If the link is off, the core performs `ufshcd_reset_and_restore()` (drivers/ufs/core/ufshcd.c:10034). - Hence, even if the vendor-specific parts hit an error, the core still executes its well-tested recovery and bring-up, which avoids the I/O hang scenario the commit message calls out.
- Localized change, minimal risk: - The change is confined to one function in the Mediatek UFS host driver; no interface or architectural changes. - `ufshcd_link_recovery()` is the standard core recovery path for UFS (drivers/ufs/core/ufshcd.c:4467), which resets the device and host and is safe to invoke on failures. - Logging uses existing runtime PM fields for debugging and has no functional side effects.
- Side effects considered: - Masking the error return from `ufshcd_link_recovery()` at the variant level does not hide failures overall: subsequent core steps will still return errors if the link/device is not brought back correctly, and the resume wrapper will report failure (drivers/ufs/core/ufshcd.c:10011+ path). - This approach improves robustness by ensuring core recovery always runs, which is preferable to aborting early and risking an unrecovered link and stuck I/O.
- Stable backport criteria: - Fixes a user-visible bug (I/O hang after resume failures). - Patch is small, self-contained, and limited to Mediatek UFS host driver. - No new features or API changes; follows existing error-handling patterns (attempt recovery, proceed to core recovery, log details). - Low regression risk relative to the severity of the hang it prevents.
Conclusion: This is a targeted bug fix that prevents I/O hangs by ensuring the core resume/recovery sequence runs even if the vendor resume fails. It is suitable for backporting to stable.
drivers/ufs/host/ufs-mediatek.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/drivers/ufs/host/ufs-mediatek.c b/drivers/ufs/host/ufs-mediatek.c index bb0be6bed1bca..188f90e468c41 100644 --- a/drivers/ufs/host/ufs-mediatek.c +++ b/drivers/ufs/host/ufs-mediatek.c @@ -1727,8 +1727,21 @@ static int ufs_mtk_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op) }
return 0; + fail: - return ufshcd_link_recovery(hba); + /* + * Check if the platform (parent) device has resumed, and ensure that + * power, clock, and MTCMOS are all turned on. + */ + err = ufshcd_link_recovery(hba); + if (err) { + dev_err(hba->dev, "Device PM: req=%d, status:%d, err:%d\n", + hba->dev->power.request, + hba->dev->power.runtime_status, + hba->dev->power.runtime_error); + } + + return 0; /* Cannot return a failure, otherwise, the I/O will hang. */ }
static void ufs_mtk_dbg_register_dump(struct ufs_hba *hba)