[PATCH v1 1/4] scsi: ufs: allow legacy UFS devices to enable WriteBooster

[Stanley Chu <stanley.chu@mediatek.com>]

WriteBooster feature may be supported by some legacy UFS devices
(i.e., < 3.1) by upgrading firmware.

To enable WriteBooster feature in such devices, relax the entrance
condition of ufshcd_wb_probe() to allow host driver to check those
devices' WriteBooster capability.

WriteBooster feature can be available if below both conditions are
satisfied,

1. Device descriptor has dExtendedUFSFeaturesSupport field.
2. WriteBooster support is specified in above field.

Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
---
 drivers/scsi/ufs/ufshcd.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 915e963398c4..111812c5304a 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -6800,9 +6800,16 @@ static int ufshcd_scsi_add_wlus(struct ufs_hba *hba)
 
 static void ufshcd_wb_probe(struct ufs_hba *hba, u8 *desc_buf)
 {
+	if (hba->desc_size.dev_desc <= DEVICE_DESC_PARAM_EXT_UFS_FEATURE_SUP)
+		goto wb_disabled;
+
 	hba->dev_info.d_ext_ufs_feature_sup =
 		get_unaligned_be32(desc_buf +
 				   DEVICE_DESC_PARAM_EXT_UFS_FEATURE_SUP);
+
+	if (!(hba->dev_info.d_ext_ufs_feature_sup & UFS_DEV_WRITE_BOOSTER_SUP))
+		goto wb_disabled;
+
 	/*
 	 * WB may be supported but not configured while provisioning.
 	 * The spec says, in dedicated wb buffer mode,
@@ -6818,11 +6825,12 @@ static void ufshcd_wb_probe(struct ufs_hba *hba, u8 *desc_buf)
 	hba->dev_info.b_presrv_uspc_en =
 		desc_buf[DEVICE_DESC_PARAM_WB_PRESRV_USRSPC_EN];
 
-	if (!((hba->dev_info.d_ext_ufs_feature_sup &
-		 UFS_DEV_WRITE_BOOSTER_SUP) &&
-		hba->dev_info.b_wb_buffer_type &&
+	if (!(hba->dev_info.b_wb_buffer_type &&
 	      hba->dev_info.d_wb_alloc_units))
-		hba->caps &= ~UFSHCD_CAP_WB_EN;
+		goto wb_disabled;
+
+wb_disabled:
+	hba->caps &= ~UFSHCD_CAP_WB_EN;
 }
 
 static int ufs_get_device_desc(struct ufs_hba *hba)
@@ -6862,8 +6870,7 @@ static int ufs_get_device_desc(struct ufs_hba *hba)
 
 	model_index = desc_buf[DEVICE_DESC_PARAM_PRDCT_NAME];
 
-	/* Enable WB only for UFS-3.1 */
-	if (dev_info->wspecversion >= 0x310)
+	if (ufshcd_is_wb_allowed(hba))
 		ufshcd_wb_probe(hba, desc_buf);
 
 	err = ufshcd_read_string_desc(hba, model_index,
-- 
2.18.0
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