[PATCH] arm: mvebu: x240: Use i2c-gpio instead of built in controller

[Stefan Roese]

Hi Chris,

On 7/20/23 23:01, Chris Packham wrote:
> Hi Me,
> 
> On Thu, Jul 20, 2023 at 3:03 PM Chris Packham <judge.packham at gmail.com> wrote:
>>
>> There is an Errata with the built-in I2C controller where various I2C
>> hardware errors cause a complete lockup of the CPU (which eventually
>> results in an watchdog reset).
>>
>> Put the I2C MPP pins into GPIO mode and use the i2c-gpio driver instead.
>> This uses a bit-banged implementation of an I2C controller and avoids
>> triggering the Errata.
>>
>> Signed-off-by: Chris Packham <judge.packham at gmail.com>
>> ---
>> This is dependent on a bug-fix for the i2c-gpio driver I just sent
>> out[1] (sorry I should have sent them as a series but I thought this
>> would take me longer to test than it did).
>>
>> [1] - https://lore.kernel.org/u-boot/20230720023107.1184147-1-judge.packham@gmail.com/
>>
>>   arch/arm/dts/ac5-98dx35xx-atl-x240.dts | 30 ++++++++++++++++++++++----
>>   configs/x240_defconfig                 |  1 +
>>   2 files changed, 27 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm/dts/ac5-98dx35xx-atl-x240.dts b/arch/arm/dts/ac5-98dx35xx-atl-x240.dts
>> index 820ec18b4355..d47220520b9e 100644
>> --- a/arch/arm/dts/ac5-98dx35xx-atl-x240.dts
>> +++ b/arch/arm/dts/ac5-98dx35xx-atl-x240.dts
>> @@ -71,8 +71,25 @@
>>   };
>>
>>   &i2c0 {
>> -       status = "okay";
>> +       status = "disabled";
>> +};
> 
> I'll remove this section completely. I did want to make it clear that
> we're using the same pins just as GPIOs instead of the dedicated I2C
> mode which has issues but that can be explained better in the commit
> message.
> 
>>
>> +&{/} {
> 
> I should probably move this part up to the root node rather than
> addressing it here.

All these comments sound like a "good think" to do.

Feel free to add my:

Reviewed-by: Stefan Roese <sr at denx.de>

in the next version.

Thanks,
Stefan

>> +       i2cgpio: i2c-gpio-0 {
>> +                       compatible = "i2c-gpio";
>> +                       #address-cells = <1>;
>> +                       #size-cells = <0>;
>> +
>> +                       pinctrl-names = "default";
>> +                       pinctrl-0 =  <&i2c0_gpio>;
>> +                       scl-gpios = <&gpio0 26 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
>> +                       sda-gpios = <&gpio0 27 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
>> +                       i2c-gpio,delay-us = <2>;
>> +                       status = "okay";
>> +                };
>> +};
>> +
>> +&i2cgpio {
>>          mux at 71 {
>>                  #address-cells = <1>;
>>                  #size-cells = <0>;
>> @@ -177,8 +194,8 @@
>>           * LED_OE_N              [23]
>>           * USB_PWR_FLT_N         [24]
>>           * SFP_INT_N             [25]
>> -        * I2C0_SCL              [26]
>> -        * I2C0_SDA              [27]
>> +        * I2C0_SCL              [26] (GPIO)
>> +        * I2C0_SDA              [27] (GPIO)
>>           * USB_EN                [28]
>>           * MONITOR_INT_N         [29]
>>           * XM1_MDC               [30]
>> @@ -201,7 +218,7 @@
>>          /*           0    1    2    3    4    5    6    7    8    9 */
>>          pin-func = < 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff
>>                       0xff 0xff 1    1    1    1    0xff 0xff 0    0
>> -                    0    0    0    0    0    0    1    1    0    0
>> +                    0    0    0    0    0    0    0xff 0xff 0    0
>>                       1    1    1    1    0    0    0    0    0    0
>>                       0    0    0    1    1    1    >;
>>
>> @@ -209,4 +226,9 @@
>>                  marvell,pins = <0 1 2 3 4 5 6 7 8 9 10 11 16 17>;
>>                  marvell,function = <2>;
>>          };
>> +
>> +       i2c0_gpio: i2c0-gpio-pins {
>> +               marvell,pins = <26 27>;
>> +               marvell,function = <0>;
>> +       };
>>   };
>> diff --git a/configs/x240_defconfig b/configs/x240_defconfig
>> index 6d25c5ae3fcf..e8589d636081 100644
>> --- a/configs/x240_defconfig
>> +++ b/configs/x240_defconfig
>> @@ -43,6 +43,7 @@ CONFIG_CLK_MVEBU=y
>>   CONFIG_GPIO_HOG=y
>>   CONFIG_DM_PCA953X=y
>>   CONFIG_DM_I2C=y
>> +CONFIG_DM_I2C_GPIO=y
>>   CONFIG_SYS_I2C_MVTWSI=y
>>   CONFIG_I2C_MUX=y
>>   CONFIG_I2C_MUX_PCA954x=y
>> --
>> 2.41.0
>>

Viele Grüße,
Stefan Roese

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