[PATCH v2 10/13] ufs: Add missing memory barriers

[neil.armstrong at linaro.org]

From: Bhupesh Sharma <bhupesh.linux at gmail.com>

Add missing wmb() and mb() barriers in the u-boot UFS core
framework driver to allow registers updates to happen before
follow-up read operations.

This makes the barrier placement similar to the Linux UFS driver,
synced from the Linux v6.9 release.

Starting from the v6.10 release, the barriers were replaced with a register
read-back in [1], this will ported to u-boot in a second time.

[1] https://lore.kernel.org/all/20240329-ufs-reset-ensure-effect-before-delay-v5-0-181252004586@redhat.com/

Signed-off-by: Bhupesh Sharma <bhupesh.sharma at linaro.org>
Tested-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu at amd.com>
---
 drivers/ufs/ufs.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/ufs/ufs.c b/drivers/ufs/ufs.c
index 565a6af1404..5d4e5424358 100644
--- a/drivers/ufs/ufs.c
+++ b/drivers/ufs/ufs.c
@@ -432,6 +432,12 @@ static int ufshcd_make_hba_operational(struct ufs_hba *hba)
 	ufshcd_writel(hba, upper_32_bits((dma_addr_t)hba->utmrdl),
 		      REG_UTP_TASK_REQ_LIST_BASE_H);
 
+	/*
+	 * Make sure base address and interrupt setup are updated before
+	 * enabling the run/stop registers below.
+	 */
+	wmb();
+
 	/*
 	 * UCRDY, UTMRLDY and UTRLRDY bits must be 1
 	 */
@@ -861,6 +867,9 @@ static int ufshcd_send_command(struct ufs_hba *hba, unsigned int task_tag)
 
 	ufshcd_writel(hba, 1 << task_tag, REG_UTP_TRANSFER_REQ_DOOR_BELL);
 
+	/* Make sure doorbell reg is updated before reading interrupt status */
+	wmb();
+
 	start = get_timer(0);
 	do {
 		intr_status = ufshcd_readl(hba, REG_INTERRUPT_STATUS);
@@ -1994,6 +2003,8 @@ int ufshcd_probe(struct udevice *ufs_dev, struct ufs_hba_ops *hba_ops)
 		      REG_INTERRUPT_STATUS);
 	ufshcd_writel(hba, 0, REG_INTERRUPT_ENABLE);
 
+	mb();
+
 	err = ufshcd_hba_enable(hba);
 	if (err) {
 		dev_err(hba->dev, "Host controller enable failed\n");

-- 
2.34.1