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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 <max.senia.poliak@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44476
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
This commit is contained in:
Maxim Polyakov 2020-06-20 17:26:21 +03:00 committed by Nico Huber
parent 0af1926353
commit aa99830c06
2 changed files with 25 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
src/ec/kontron/kempld/chip.h
View File

@ -12,6 +12,13 @@ enum kempld_uart_io {
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 kempld_uart {
struct ec_kontron_kempld_config {
struct kempld_uart uart[KEMPLD_NUM_UARTS];
unsigned short i2c_frequency;
};
#endif /* EC_KONTRON_KEMPLD_CHIP_H */

23
src/ec/kontron/kempld/kempld_i2c.c
View File

@ -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 @@ static struct device_operations kempld_i2c_dev_ops = {
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 @@ void kempld_i2c_device_init(struct device *const dev)
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;