[PATCH V7 3/4] i3c: master: Add endianness support for i3c_readl_fifo() and i3c_writel_fifo()

Manikanta Guntupalli
2025-09-23T15:46:47Z

Add endianness handling to the FIFO access helpers i3c_readl_fifo() and
i3c_writel_fifo(). This ensures correct data transfers on platforms where
the FIFO registers are expected to be accessed in either big-endian or
little-endian format.

Update the Synopsys, Cadence, and Renesas I3C master controller drivers to
pass the appropriate endianness argument to these helpers.

Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com>
---
Changes since V7:
This patch introduced in V7.
---
drivers/i3c/internals.h | 35 +++++++++++++++++++++++-----
drivers/i3c/master/dw-i3c-master.c | 9 ++++---
drivers/i3c/master/i3c-master-cdns.c | 9 ++++---
drivers/i3c/master/renesas-i3c.c | 12 ++++++----
4 files changed, 49 insertions(+), 16 deletions(-)

diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h
index 0d857cc68cc5..399bbf006dcd 100644
--- a/drivers/i3c/internals.h
+++ b/drivers/i3c/internals.h
@@ -24,21 +24,35 @@ int i3c_dev_request_ibi_locked(struct i3c_dev_desc *dev,
const struct i3c_ibi_setup *req);
void i3c_dev_free_ibi_locked(struct i3c_dev_desc *dev);

+enum i3c_fifo_endian {
+ I3C_FIFO_LITTLE_ENDIAN,
+ I3C_FIFO_BIG_ENDIAN,
+};
+
/**
* i3c_writel_fifo - Write data buffer to 32bit FIFO
* @addr: FIFO Address to write to
* @buf: Pointer to the data bytes to write
* @nbytes: Number of bytes to write
+ * @endian: Endianness of FIFO write
*/
static inline void i3c_writel_fifo(void __iomem *addr, const void *buf,
- int nbytes)
+ int nbytes, enum i3c_fifo_endian endian)
{
- writesl(addr, buf, nbytes / 4);
+ if (endian)
+ writesl_be(addr, buf, nbytes / 4);
+ else
+ writesl(addr, buf, nbytes / 4);
+
if (nbytes & 3) {
u32 tmp = 0;

memcpy(&tmp, buf + (nbytes & ~3), nbytes & 3);
- writel(tmp, addr);
+
+ if (endian)
+ writel_be(tmp, addr);
+ else
+ writel(tmp, addr);
}
}

@@ -47,15 +61,24 @@ static inline void i3c_writel_fifo(void __iomem *addr, const void *buf,
* @addr: FIFO Address to read from
* @buf: Pointer to the buffer to store read bytes
* @nbytes: Number of bytes to read
+ * @endian: Endianness of FIFO read
*/
static inline void i3c_readl_fifo(const void __iomem *addr, void *buf,
- int nbytes)
+ int nbytes, enum i3c_fifo_endian endian)
{
- readsl(addr, buf, nbytes / 4);
+ if (endian)
+ readsl_be(addr, buf, nbytes / 4);
+ else
+ readsl(addr, buf, nbytes / 4);
+
if (nbytes & 3) {
u32 tmp;

- tmp = readl(addr);
+ if (endian)
+ tmp = readl_be(addr);
+ else
+ tmp = readl(addr);
+
memcpy(buf + (nbytes & ~3), &tmp, nbytes & 3);
}
}
diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
index 974122b2d20e..5d723ac041c2 100644
--- a/drivers/i3c/master/dw-i3c-master.c
+++ b/drivers/i3c/master/dw-i3c-master.c
@@ -337,19 +337,22 @@ static int dw_i3c_master_get_free_pos(struct dw_i3c_master *master)
static void dw_i3c_master_wr_tx_fifo(struct dw_i3c_master *master,
const u8 *bytes, int nbytes)
{
- i3c_writel_fifo(master->regs + RX_TX_DATA_PORT, bytes, nbytes);
+ i3c_writel_fifo(master->regs + RX_TX_DATA_PORT, bytes, nbytes,
+ I3C_FIFO_LITTLE_ENDIAN);
}

static void dw_i3c_master_read_rx_fifo(struct dw_i3c_master *master,
u8 *bytes, int nbytes)
{
- i3c_readl_fifo(master->regs + RX_TX_DATA_PORT, bytes, nbytes);
+ i3c_readl_fifo(master->regs + RX_TX_DATA_PORT, bytes, nbytes,
+ I3C_FIFO_LITTLE_ENDIAN);
}

static void dw_i3c_master_read_ibi_fifo(struct dw_i3c_master *master,
u8 *bytes, int nbytes)
{
- i3c_readl_fifo(master->regs + IBI_QUEUE_STATUS, bytes, nbytes);
+ i3c_readl_fifo(master->regs + IBI_QUEUE_STATUS, bytes, nbytes,
+ I3C_FIFO_LITTLE_ENDIAN);
}

static struct dw_i3c_xfer *
diff --git a/drivers/i3c/master/i3c-master-cdns.c b/drivers/i3c/master/i3c-master-cdns.c
index 97b151564d3d..de3b5e894b4b 100644
--- a/drivers/i3c/master/i3c-master-cdns.c
+++ b/drivers/i3c/master/i3c-master-cdns.c
@@ -428,13 +428,15 @@ to_cdns_i3c_master(struct i3c_master_controller *master)
static void cdns_i3c_master_wr_to_tx_fifo(struct cdns_i3c_master *master,
const u8 *bytes, int nbytes)
{
- i3c_writel_fifo(master->regs + TX_FIFO, bytes, nbytes);
+ i3c_writel_fifo(master->regs + TX_FIFO, bytes, nbytes,
+ I3C_FIFO_LITTLE_ENDIAN);
}

static void cdns_i3c_master_rd_from_rx_fifo(struct cdns_i3c_master *master,
u8 *bytes, int nbytes)
{
- i3c_readl_fifo(master->regs + RX_FIFO, bytes, nbytes);
+ i3c_readl_fifo(master->regs + RX_FIFO, bytes, nbytes,
+ I3C_FIFO_LITTLE_ENDIAN);
}

static bool cdns_i3c_master_supports_ccc_cmd(struct i3c_master_controller *m,
@@ -1319,7 +1321,8 @@ static void cdns_i3c_master_handle_ibi(struct cdns_i3c_master *master,
buf = slot->data;

nbytes = IBIR_XFER_BYTES(ibir);
- i3c_readl_fifo(master->regs + IBI_DATA_FIFO, buf, nbytes);
+ i3c_readl_fifo(master->regs + IBI_DATA_FIFO, buf, nbytes,
+ I3C_FIFO_LITTLE_ENDIAN);

slot->len = min_t(unsigned int, IBIR_XFER_BYTES(ibir),
dev->ibi->max_payload_len);
diff --git a/drivers/i3c/master/renesas-i3c.c b/drivers/i3c/master/renesas-i3c.c
index 174d3dc5d276..5610cf71740e 100644
--- a/drivers/i3c/master/renesas-i3c.c
+++ b/drivers/i3c/master/renesas-i3c.c
@@ -835,7 +835,8 @@ static int renesas_i3c_priv_xfers(struct i3c_dev_desc *dev, struct i3c_priv_xfer
}

if (!i3c_xfers[i].rnw && i3c_xfers[i].len > 4) {
- i3c_writel_fifo(i3c->regs + NTDTBP0, cmd->tx_buf, cmd->len);
+ i3c_writel_fifo(i3c->regs + NTDTBP0, cmd->tx_buf, cmd->len,
+ I3C_FIFO_LITTLE_ENDIAN);
if (cmd->len > NTDTBP0_DEPTH * sizeof(u32))
renesas_set_bit(i3c->regs, NTIE, NTIE_TDBEIE0);
}
@@ -1021,7 +1022,8 @@ static irqreturn_t renesas_i3c_tx_isr(int irq, void *data)
/* Clear the Transmit Buffer Empty status flag. */
renesas_clear_bit(i3c->regs, NTST, NTST_TDBEF0);
} else {
- i3c_writel_fifo(i3c->regs + NTDTBP0, cmd->tx_buf, cmd->len);
+ i3c_writel_fifo(i3c->regs + NTDTBP0, cmd->tx_buf, cmd->len,
+ I3C_FIFO_LITTLE_ENDIAN);
}
}

@@ -1061,7 +1063,8 @@ static irqreturn_t renesas_i3c_resp_isr(int irq, void *data)
if (NDBSTLV0_RDBLV(renesas_readl(i3c->regs, NDBSTLV0)) && !cmd->err)
bytes_remaining = data_len - cmd->rx_count;

- i3c_readl_fifo(i3c->regs + NTDTBP0, cmd->rx_buf, bytes_remaining);
+ i3c_readl_fifo(i3c->regs + NTDTBP0, cmd->rx_buf, bytes_remaining,
+ I3C_FIFO_LITTLE_ENDIAN);
renesas_clear_bit(i3c->regs, NTIE, NTIE_RDBFIE0);
break;
default:
@@ -1203,7 +1206,8 @@ static irqreturn_t renesas_i3c_rx_isr(int irq, void *data)
cmd->i2c_bytes_left--;
} else {
read_bytes = NDBSTLV0_RDBLV(renesas_readl(i3c->regs, NDBSTLV0)) * sizeof(u32);
- i3c_readl_fifo(i3c->regs + NTDTBP0, cmd->rx_buf, read_bytes);
+ i3c_readl_fifo(i3c->regs + NTDTBP0, cmd->rx_buf, read_bytes,
+ I3C_FIFO_LITTLE_ENDIAN);
cmd->rx_count = read_bytes;
}

--
2.34.1