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i2c: rtl9300: add support for 50 kHz and 2.5 MHz bus speeds

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Some SFP modules on certain switches (for example the ONTi ONT-S508CL-8S and
XikeStor SKS8300-8X) exhibit unreliable I2C communication at the currently
supported speeds. Add support for 50 kHz and 2.5 MHz I2C bus modes on the
RTL9300 to improve compatibility with these devices.

Signed-off-by: Jan Kantert <jan-kernel@kantert.net>
Reviewed-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260227111134.2163701-1-jan-kernel@kantert.net
This commit is contained in:
Jan Kantert 2026-02-27 12:11:34 +01:00 committed by Andi Shyti
parent d3e2c7476e
commit 879766b58e
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GPG Key ID: DA78056626D32D6E
1 changed files with 14 additions and 2 deletions
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16
drivers/i2c/busses/i2c-rtl9300.c
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@ -11,10 +11,16 @@
#include <linux/unaligned.h>
enum rtl9300_bus_freq {
RTL9300_I2C_STD_FREQ,
RTL9300_I2C_FAST_FREQ,
RTL9300_I2C_STD_FREQ, // 100kHz
RTL9300_I2C_FAST_FREQ, // 400kHz
RTL9300_I2C_SUPER_FAST_FREQ, // 2.5MHz
RTL9300_I2C_SLOW_FREQ, // 50kHz
};
#define RTL9300_I2C_MAX_SUPER_FAST_FREQ 2500000
#define RTL9300_I2C_MAX_SLOW_FREQ 50000
struct rtl9300_i2c;
struct rtl9300_i2c_chan {
@ -433,6 +439,12 @@ static int rtl9300_i2c_probe(struct platform_device *pdev)
case I2C_MAX_FAST_MODE_FREQ:
chan->bus_freq = RTL9300_I2C_FAST_FREQ;
break;
case RTL9300_I2C_MAX_SUPER_FAST_FREQ:
chan->bus_freq = RTL9300_I2C_SUPER_FAST_FREQ;
break;
case RTL9300_I2C_MAX_SLOW_FREQ:
chan->bus_freq = RTL9300_I2C_SLOW_FREQ;
break;
default:
dev_warn(i2c->dev, "SDA%d clock-frequency %d not supported using default\n",
sda_num, clock_freq);