[PATCH V1 1/2] scsi: ufs: core: Add UFSHCD_QUIRK_SKIP_DEVICE_RESET quirk

[Nitin Rawat]

Add a new host quirk UFSHCD_QUIRK_SKIP_DEVICE_RESET to allow host
controller drivers to skip asserting device reset during UFS power
down.

When RST_N is asserted, the UFS device firmware wakes up and executes
its internal reset routine. This routine initializes multiple hardware
blocks and causing the device to draw a large curreny during this time.
If the power rail transitions to LPM (Low Power Mode) while the device
is still drawing this elevated current, it may trigger an
OCP (Over Current Protection) fault in the regulator.

For some UFS devices (e.g., Micron), the elevated current draw persists
until the reset line is deasserted, making a fixed delay insufficient
to prevent OCP. This quirk allows such devices to skip device reset
during UFS power down. The device reset will instead be asserted as
part of the platform shutdown sequence.

Signed-off-by: Nitin Rawat <nitin.rawat@xxxxxxxxxxxxxxxx>
---
 include/ufs/ufshcd.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
index 3eaae082329c..18d634499ce5 100644
--- a/include/ufs/ufshcd.h
+++ b/include/ufs/ufshcd.h
@@ -813,6 +813,20 @@ enum ufshcd_quirks {
 	 * allowed by M-PHY spec ver 6.0.
 	 */
 	UFSHCD_QUIRK_EXTENDED_TX_EQTR_ADAPT_LENGTH_L0L1L2L3	= 1 << 28,
+
+	/*
+	 * Some UFS devices keep drawing larger current after reset is
+	 * asserted until it is deasserted. Asserting device reset
+	 * during UFS power down causes the device firmware to wake up and
+	 * execute its reset routine, drawing current beyond the permissible
+	 * limit for low-power mode (LPM). This may trigger an OCP fault on
+	 * the regulator supplying power to UFS.
+	 *
+	 * Enable this quirk to skip asserting device reset during UFS power
+	 * down. This is handled only in shutdown; the device reset will be
+	 * asserted as part of the platform shutdown sequence.
+	 */
+	UFSHCD_QUIRK_SKIP_DEVICE_RESET			= 1 << 29,
 };

 enum ufshcd_caps {
--
2.34.1