[coreboot-gerrit] Change in coreboot[master]: ec/kontron: add option to configure I2C frequency

[Maxim Polyakov (Code Review)]

Maxim Polyakov has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/44476 )

Change subject: ec/kontron: add option to configure I2C frequency
......................................................................

ec/kontron: add option to configure I2C frequency

Allows to change the frequency for the I2C bus by overriding i2c_freq_khz
option from the devicetree of the board.

Tested on Kontron mAL10 COMe module with T10-TNI carrierboard [1,2].

[1] https: //review.coreboot.org/c/coreboot/+/39133
[2] https: //review.coreboot.org/c/coreboot/+/39846

Change-Id: If0eb477af10d00eb4f17f9c01209f170b746ad3d
Signed-off-by: Maxim Polyakov 
---
M src/ec/kontron/kempld/chip.h
M src/ec/kontron/kempld/kempld_i2c.c
2 files changed, 22 insertions(+), 4 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/76/44476/1

diff --git a/src/ec/kontron/kempld/chip.h b/src/ec/kontron/kempld/chip.h
index 8ca8d24..2ac0949 100644
--- a/src/ec/kontron/kempld/chip.h
+++ b/src/ec/kontron/kempld/chip.h
@@ -19,6 +19,7 @@

struct ec_kontron_kempld_config {
    struct kempld_uart uart[KEMPLD_NUM_UARTS];
+	unsigned short     i2c_freq_khz;
 };

#endif /* EC_KONTRON_KEMPLD_CHIP_H */
diff --git a/src/ec/kontron/kempld/kempld_i2c.c b/src/ec/kontron/kempld/kempld_i2c.c
index 296cf76..9ba2f71 100644
--- a/src/ec/kontron/kempld/kempld_i2c.c
+++ b/src/ec/kontron/kempld/kempld_i2c.c
@@ -13,6 +13,7 @@
 #include <timer.h>
 #include <delay.h>

+#include "chip.h"
 #include "kempld.h"
 #include "kempld_internal.h"

@@ -40,8 +41,8 @@
 #define  I2C_CMD_READ_NACK	0x29
 #define  I2C_CMD_IACK		0x01

-#define KEMPLD_I2C_FREQ_MAX	2700	/* 2.7 mHz */
-#define KEMPLD_I2C_FREQ_STD	100	/* 100 kHz */
+#define KEMPLD_I2C_FREQ_MAX			2700 /* 2.7 mHz */
+#define KEMPLD_I2C_FREQ_STD_DEFAULT		100  /* 100 kHz */

#define EIO		  5
 #define ENXIO		  6
@@ -230,12 +231,17 @@

void kempld_i2c_device_init(struct device *const dev)
 {
+	const struct ec_kontron_kempld_config *const config = dev->chip_info;
+	unsigned short frequency;
    u16 prescale_corr;
    long prescale;
    u8 ctrl;
    u8 stat;
    u8 cfg;

+	if (!config)
+		return;
+
    if (kempld_get_mutex(100) < 0)
    	return;

@@ -244,11 +250,22 @@
    ctrl &= ~(I2C_CTRL_EN | I2C_CTRL_IEN);
    kempld_write8(KEMPLD_I2C_CTRL, ctrl);

+	frequency = KEMPLD_I2C_FREQ_STD_DEFAULT;
+	if (config->i2c_freq_khz) {
+		if (config->i2c_freq_khz <= KEMPLD_I2C_FREQ_MAX)
+			frequency = config->i2c_freq_khz;
+		else
+			printk(BIOS_WARNING,
+				"kempld_i2c: %d kHz is an invalid frequency value\n",
+				config->i2c_freq_khz);
+	}
+	printk(BIOS_INFO, "kempld_i2c: Use frequency %d\n", frequency);
+
    const u8 spec_major = KEMPLD_SPEC_GET_MAJOR(kempld_read8(KEMPLD_SPEC));
    if (spec_major == 1)
-		prescale = KEMPLD_CLK / (KEMPLD_I2C_FREQ_STD * 5) - 1000;
+		prescale = KEMPLD_CLK / (frequency * 5) - 1000;
    else
-		prescale = KEMPLD_CLK / (KEMPLD_I2C_FREQ_STD * 4) - 3000;
+		prescale = KEMPLD_CLK / (frequency * 4) - 3000;

if (prescale < 0)
    	prescale = 0;