Subject: [PATCH v2 1/2] mfd: rsmu: fix page register setup

From: Matthew Bystrin <[email-masked]>
Date: Wed, 29 Apr 2026 10:20:46 +0300

Fix writes to page register in 8A3400x family (Clock Matrix).

All calls to rsmu_write_page_register() (both in i2c and spi) have
resulted in early return, becase all addresses in
include/linux/mfd/idt8a340_reg.h are less than RSMU_CM_SCSR_BASE.

There were 2 separate patch series which have to be merged in one time:
mfd and ptp. The latter have been merged, the former[1] have not.

Link: https://lore.kernel.org/netdev/[email-masked]/
Fixes: 67d6c76fc815 ("mfd: rsmu: Support 32-bit address space")
Signed-off-by: Matthew Bystrin <[email-masked]>
---
 drivers/mfd/rsmu_i2c.c | 6 +-----
 drivers/mfd/rsmu_spi.c | 5 +----
 2 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/mfd/rsmu_i2c.c b/drivers/mfd/rsmu_i2c.c
index cba64f107a2f..9e5fc8259eec 100644
--- a/drivers/mfd/rsmu_i2c.c
+++ b/drivers/mfd/rsmu_i2c.c
@@ -134,14 +134,10 @@ static int rsmu_i2c_write_device(struct rsmu_ddata *rsmu, u8 reg, u8 *buf, u8 by
 static int rsmu_write_page_register(struct rsmu_ddata *rsmu, u32 reg,
 				    rsmu_rw_device rsmu_write_device)
 {
-	u32 page = reg & RSMU_CM_PAGE_MASK;
+	u32 page = (reg | RSMU_CM_SCSR_BASE) & RSMU_CM_PAGE_MASK;
 	u8 buf[4];
 	int err;
 
-	/* Do not modify offset register for none-scsr registers */
-	if (reg < RSMU_CM_SCSR_BASE)
-		return 0;
-
 	/* Simply return if we are on the same page */
 	if (rsmu->page == page)
 		return 0;
diff --git a/drivers/mfd/rsmu_spi.c b/drivers/mfd/rsmu_spi.c
index 39d9be1e141f..c931d8cea0a1 100644
--- a/drivers/mfd/rsmu_spi.c
+++ b/drivers/mfd/rsmu_spi.c
@@ -101,11 +101,8 @@ static int rsmu_write_page_register(struct rsmu_ddata *rsmu, u32 reg)
 
 	switch (rsmu->type) {
 	case RSMU_CM:
-		/* Do not modify page register for none-scsr registers */
-		if (reg < RSMU_CM_SCSR_BASE)
-			return 0;
 		page_reg = RSMU_CM_PAGE_ADDR;
-		page = reg & RSMU_PAGE_MASK;
+		page = (reg | RSMU_CM_SCSR_BASE) & RSMU_PAGE_MASK;
 		buf[0] = (u8)(page & 0xFF);
 		buf[1] = (u8)((page >> 8) & 0xFF);
 		buf[2] = (u8)((page >> 16) & 0xFF);
-- 
2.53.0