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

[Nico Huber (Code Review)]

Nico Huber has submitted this change. ( https://review.coreboot.org/c/coreboot/+/44476 )

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

ec/kontron/kempld: add option to configure I2C frequency

Allows to change the I2C bus frequency by overriding i2c_frequency
option from the board devicetree. Thus, the I2C controller can use
Fast-mode (Fm), with a bit rate up to 400 kbit/s and Fast-mode Plus
(Fm+), with a bit rate up to 1 Mbit/s [1].

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

[1] I2C-bus specification and user manual, doc #UM10204, Rev. 6,
    4 April 2014.
[2] https://review.coreboot.org/c/coreboot/+/39133

Change-Id: If0eb477af10d00eb4f17f9c01209f170b746ad3d
Signed-off-by: Maxim Polyakov 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44476
Reviewed-by: Angel Pons 
Reviewed-by: Nico Huber 
Tested-by: build bot (Jenkins) 
---
M src/ec/kontron/kempld/chip.h
M src/ec/kontron/kempld/kempld_i2c.c
2 files changed, 25 insertions(+), 6 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Nico Huber: Looks good to me, approved
  Angel Pons: Looks good to me, approved

diff --git a/src/ec/kontron/kempld/chip.h b/src/ec/kontron/kempld/chip.h
index 8ca8d24..30f40fe 100644
--- a/src/ec/kontron/kempld/chip.h
+++ b/src/ec/kontron/kempld/chip.h
@@ -12,6 +12,13 @@
    KEMPLD_UART_2E8 = 3,
 };

+enum kempld_i2c_frequency {
+	KEMPLD_I2C_FREQ_STANDARD_MODE_100KHZ	= 100,
+	KEMPLD_I2C_FREQ_FAST_MODE_400KHZ	= 400,
+	KEMPLD_I2C_FREQ_FAST_PLUS_MODE_1MHZ	= 1000,
+	KEMPLD_I2C_FREQ_MAX			= 2700,
+};
+
 struct kempld_uart {
    enum kempld_uart_io io;
    unsigned int irq;
@@ -19,6 +26,7 @@

struct ec_kontron_kempld_config {
    struct kempld_uart uart[KEMPLD_NUM_UARTS];
+	unsigned short i2c_frequency;
 };

#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..8abbb4b 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"

@@ -40,9 +41,6 @@
 #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 EIO		  5
 #define ENXIO		  6
 #define EAGAIN		 11
@@ -230,7 +228,8 @@

void kempld_i2c_device_init(struct device *const dev)
 {
-	u16 prescale_corr;
+	const struct ec_kontron_kempld_config *const config = dev->chip_info;
+	u16 prescale_corr, frequency;
    long prescale;
    u8 ctrl;
    u8 stat;
@@ -244,11 +243,23 @@
    ctrl &= ~(I2C_CTRL_EN | I2C_CTRL_IEN);
    kempld_write8(KEMPLD_I2C_CTRL, ctrl);

+	frequency = KEMPLD_I2C_FREQ_STANDARD_MODE_100KHZ;
+	if (config && config->i2c_frequency) {
+		if (config->i2c_frequency <= KEMPLD_I2C_FREQ_MAX) {
+			frequency = config->i2c_frequency;
+		} else {
+			printk(BIOS_NOTICE,
+				"kempld_i2c: %d kHz is too high!\n",
+				config->i2c_frequency);
+		}
+	}
+	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;