[PATCH AUTOSEL 6.17-6.12] scsi: ufs: host: mediatek: Fix unbalanced IRQ enable issue

[Sasha Levin <sashal@kernel.org>]

From: Peter Wang <peter.wang@mediatek.com>

[ Upstream commit 91cad911edd1612ed28f5cfb2d4c53a8824951a5 ]

Resolve the issue of unbalanced IRQ enablement by setting the
'is_mcq_intr_enabled' flag after the first successful IRQ enablement.
Ensure proper tracking of the IRQ state and prevent potential mismatches
in IRQ handling.

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

- What it fixes
  - Prevents unbalanced IRQ enable calls in the Mediatek UFS MCQ path by
    ensuring the driver’s internal state flag matches the real IRQ state
    immediately after the IRQs are requested (and thus enabled by
    default). Without this, subsequent enable paths may re-enable
    already-enabled IRQs, triggering “unbalanced enable” warnings and
    mismatched IRQ depth accounting.

- Precise change
  - Adds `host->is_mcq_intr_enabled = true;` at the end of
    `ufs_mtk_config_mcq_irq()` after all IRQ handlers have been
    successfully registered with `devm_request_irq()`
    (drivers/ufs/host/ufs-mediatek.c:2193).
    - This reflects that IRQs are enabled as a result of `request_irq()`
      and aligns the state flag with reality.

- Why it’s correct
  - `devm_request_irq()` attaches the handler and leaves the IRQ enabled
    by default. If the state flag remains false, the first call into the
    driver’s “enable MCQ IRQs” helper will re-enable an already-enabled
    IRQ, causing an unbalanced enable.
  - The driver already guards enable/disable with this flag:
    - Disable path: sets the flag false after disabling
      (drivers/ufs/host/ufs-mediatek.c:741).
    - Enable path: bails out if already enabled and sets the flag true
      only after enabling (drivers/ufs/host/ufs-mediatek.c:755 and
      drivers/ufs/host/ufs-mediatek.c:762).
  - With the new line in `ufs_mtk_config_mcq_irq()`
    (drivers/ufs/host/ufs-mediatek.c:2193), the initial state is
    correct, so `ufs_mtk_mcq_enable_irq()` will correctly no-op on the
    first enable attempt when IRQs are already enabled.

- How the bug manifested
  - `ufs_mtk_setup_clocks()`’s POST_CHANGE flow calls
    `ufs_mtk_mcq_enable_irq()` (drivers/ufs/host/ufs-mediatek.c:817).
    Before this patch, after `devm_request_irq()` the IRQs were already
    enabled but `is_mcq_intr_enabled` was still false, so the enable
    path would call `enable_irq()` again, risking “unbalanced IRQ
    enable” warnings.
  - The disable path is already consistent: `ufs_mtk_mcq_disable_irq()`
    uses the list of IRQs and flips the flag to false
    (drivers/ufs/host/ufs-mediatek.c:741), so subsequent enables are
    properly balanced.

- Scope and risk
  - Change is a single-line state fix in one driver function, confined
    to the Mediatek UFS host driver.
  - No API, ABI, or architectural changes; no behavioral changes beyond
    preventing an incorrect extra `enable_irq()`.
  - The flag is set only after all IRQ requests succeed; if any
    `devm_request_irq()` fails, the function returns early and does not
    set the flag, preserving prior behavior.

- Stable backport criteria
  - Fixes a real correctness issue that can lead to warnings and IRQ
    depth mismatches.
  - Small, contained, and low risk.
  - No feature addition; clear bug fix in a specific subsystem (SCSI UFS
    Mediatek host).

Given the above, this is a good candidate for stable backporting
wherever the Mediatek UFS MCQ driver and `is_mcq_intr_enabled` field
exist.

 drivers/ufs/host/ufs-mediatek.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/ufs/host/ufs-mediatek.c b/drivers/ufs/host/ufs-mediatek.c
index 188f90e468c41..055b24758ca3d 100644
--- a/drivers/ufs/host/ufs-mediatek.c
+++ b/drivers/ufs/host/ufs-mediatek.c
@@ -2111,6 +2111,7 @@ static int ufs_mtk_config_mcq_irq(struct ufs_hba *hba)
 			return ret;
 		}
 	}
+	host->is_mcq_intr_enabled = true;
 
 	return 0;
 }
-- 
2.51.0