linux-kernel - [PATCH v2 1/3] i3c: master: Add inline i3c_readl_fifo() and i3c_writel

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Message-ID: <20250622-i3c-writesl-readsl-v2-1-2afd34ec6306@analog.com>
Date: Sun, 22 Jun 2025 11:18:58 +0200
From: Jorge Marques <jorge.marques@...log.com>
To: Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Frank Li
	<Frank.Li@....com>,
        Przemysław Gaj <pgaj@...ence.com>
CC: <linux-i3c@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        "Jorge
 Marques" <jorge.marques@...log.com>
Subject: [PATCH v2 1/3] i3c: master: Add inline i3c_readl_fifo() and
 i3c_writel_fifo()

The i3c abstraction excepts u8 buffers, but some controllers have a bus
width of 32-bits and don't support flagging valid bytes, so it is
required to read/write long words and to use memcpy on the remainder of
the number of bytes by 32-bits to not write/read outside the buffer
bounds.

Signed-off-by: Jorge Marques <jorge.marques@...log.com>
---
 drivers/i3c/internals.h | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h
index 433f6088b7cec8c77288ee24dbee8b18338aa1eb..88887b12122efafac81bcfdd093d943259e13a08 100644
--- a/drivers/i3c/internals.h
+++ b/drivers/i3c/internals.h
@@ -22,4 +22,41 @@ int i3c_dev_enable_ibi_locked(struct i3c_dev_desc *dev);
 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);
+
+/**
+ * i3c_master_writesl- Write bytes to long memory region from byte array
+ * @addr: Register to write to
+ * @bytes: Pointer to the data bytes to write
+ * @nbytes: Number of bytes to write
+ */
+static inline void i3c_writel_fifo(void __iomem *addr, const void *bytes,
+				   int nbytes)
+{
+	writesl(addr, bytes, nbytes / 4);
+	if (nbytes & 3) {
+		u32 tmp = 0;
+
+		memcpy(&tmp, bytes + (nbytes & ~3), nbytes & 3);
+		writel(tmp, addr);
+	}
+}
+
+/**
+ * i3c_master_readsl - Read bytes from long memory region to byte array
+ * @addr: Register to read from
+ * @bytes: Pointer to the buffer to store read bytes
+ * @nbytes: Number of bytes to read
+ */
+static inline void i3c_readl_fifo(const void __iomem *addr, void *bytes,
+				  int nbytes)
+{
+	readsl(addr, bytes, nbytes / 4);
+	if (nbytes & 3) {
+		u32 tmp;
+
+		tmp = readl(addr);
+		memcpy(bytes + (nbytes & ~3), &tmp, nbytes & 3);
+	}
+}
+
 #endif /* I3C_INTERNAL_H */

-- 
2.49.0