Commit 71c49ee9 authored by Binbin Zhou's avatar Binbin Zhou Committed by Andi Shyti
Browse files

i2c: ls2x: Fix frequency division register access 



According to the chip manual, the I2C register access type of
Loongson-2K2000/LS7A is "B", so we can only access registers in byte
form (readb()/writeb()).

Although Loongson-2K0500/Loongson-2K1000 do not have similar
constraints, register accesses in byte form also behave correctly.

Also, in hardware, the frequency division registers are defined as two
separate registers (high 8-bit and low 8-bit), so we just access them
directly as bytes.

Fixes: 015e61f0 ("i2c: ls2x: Add driver for Loongson-2K/LS7A I2C controller")
Co-developed-by: default avatarHongliang Wang <wanghongliang@loongson.cn>
Signed-off-by: default avatarHongliang Wang <wanghongliang@loongson.cn>
Signed-off-by: default avatarBinbin Zhou <zhoubinbin@loongson.cn>
Cc: stable@vger.kernel.org # v6.3+
Reviewed-by: default avatarAndy Shevchenko <andy@kernel.org>
Signed-off-by: default avatarAndi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20250220125612.1910990-1-zhoubinbin@loongson.cn
parent dd1998e2

drivers/i2c/busses/i2c-ls2x.c

+12 −4
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
 * Rewritten for mainline by Binbin Zhou <zhoubinbin@loongson.cn>

 */



#include <linux/bitfield.h>

#include <linux/bits.h>

#include <linux/completion.h>

#include <linux/device.h>
@@ -26,7 +27,8 @@ 
#include <linux/units.h>



/* I2C Registers */

#define I2C_LS2X_PRER		0x0 /* Freq Division Register(16 bits) */

#define I2C_LS2X_PRER_LO	0x0 /* Freq Division Low Byte Register */

#define I2C_LS2X_PRER_HI	0x1 /* Freq Division High Byte Register */

#define I2C_LS2X_CTR		0x2 /* Control Register */

#define I2C_LS2X_TXR		0x3 /* Transport Data Register */

#define I2C_LS2X_RXR		0x3 /* Receive Data Register */
@@ -93,6 +95,7 @@ static irqreturn_t ls2x_i2c_isr(int this_irq, void *dev_id) 
 */

static void ls2x_i2c_adjust_bus_speed(struct ls2x_i2c_priv *priv)

{

	u16 val;

	struct i2c_timings *t = &priv->i2c_t;

	struct device *dev = priv->adapter.dev.parent;

	u32 acpi_speed = i2c_acpi_find_bus_speed(dev);
@@ -104,9 +107,14 @@ static void ls2x_i2c_adjust_bus_speed(struct ls2x_i2c_priv *priv) 
	else

		t->bus_freq_hz = LS2X_I2C_FREQ_STD;



	/* Calculate and set i2c frequency. */

	writew(LS2X_I2C_PCLK_FREQ / (5 * t->bus_freq_hz) - 1,

	       priv->base + I2C_LS2X_PRER);

	/*

	 * According to the chip manual, we can only access the registers as bytes,

	 * otherwise the high bits will be truncated.

	 * So set the I2C frequency with a sequential writeb() instead of writew().

	 */

	val = LS2X_I2C_PCLK_FREQ / (5 * t->bus_freq_hz) - 1;

	writeb(FIELD_GET(GENMASK(7, 0), val), priv->base + I2C_LS2X_PRER_LO);

	writeb(FIELD_GET(GENMASK(15, 8), val), priv->base + I2C_LS2X_PRER_HI);

}



static void ls2x_i2c_init(struct ls2x_i2c_priv *priv)