Re: [PATCH] eeprom: at24: avoid adjusting offset for 24AA025E{48, 64}

[<Claudiu.Beznea@microchip.com>]

On 12.04.2021 21:29, Bartosz Golaszewski wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On Mon, Apr 12, 2021 at 9:42 AM <Claudiu.Beznea@microchip.com> wrote:
>>
>> On 07.04.2021 21:37, Bartosz Golaszewski wrote:
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>
>>> On Fri, Apr 2, 2021 at 3:24 PM Claudiu Beznea
>>> <claudiu.beznea@microchip.com> wrote:
>>>>
>>>> Some EEPROMs could be used only for MAC storage. In this case the
>>>> EEPROM areas where MACs resides could be modeled as NVMEM cells
>>>> (directly via DT bindings) such that the already available networking
>>>> infrastructure to read properly the MAC addresses (via
>>>> of_get_mac_address()). Add "atmel,24mac02e4", "atmel,24mac02e4"
>>>> compatible for the usage w/ 24AA025E{48, 64} type of EEPROMs and adapt
>>>> the driver to not do offset adjustments.
>>>>
>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
>>>> ---
>>>>
>>>> Hi Bartosz,
>>>>
>>>> For the previously available compatibles the offset adjustment is done
>>>> (probably for compatibility w/ old DT bindings?). In my scenario 24AA025E48
>>>> is used in setup with macb driver which is calling of_get_mac_address()
>>>> to get the proper NVMEM cell in EEPROM where the MAC resides and read
>>>> directly from there. We modeled the EEPROM and NVMEM cell in DT as
>>>> follows:
>>>>
>>>> &i2cnode {
>>>>         // ...
>>>>         eeprom0: eeprom0@52 {
>>>>                 compatible = "atmel,24mac02e4";
> 
> Can you point me to the datasheet for this model, google only directs
> me to this very email.

This is the datasheet:
https://ww1.microchip.com/downloads/en/DeviceDoc/24AA02E48-24AA025E48-24AA02E64-24AA025E64-Data-Sheet-20002124H.pdf

>
>>From the device tree it looks as if it was just a regular 24c02 EEPROM
> with MAC hard-coded at 250-255 bytes, is that right?

Yes, the MAC is hard-coded at 250. But using "24c02" compatible will
involve the offset adjustment in the driver (let me know if I missed
something).

Thank you,
Claudiu

> 
> Bartosz
> 
>>>>                 #address-cells = <1>;
>>>>                 #size-cells = <0>;
>>>>                 reg = <0x52>;
>>>>                 pagesize = <16>;
>>>>                 size = <256>;
>>>>                 status = "okay";
>>>>
>>>>                 eeprom0_eui48: eui48@fa {
>>>>                         reg = <0xfa 0x6>;
>>>>                 };
>>>>         };
>>>> };
>>>>
>>>> &gmac {
>>>>         // ...
>>>>
>>>>         nvmem-cells = <&eeprom0_eui48>;
>>>>         nvmem-cell-names = "mac-address";
>>>>
>>>>         // ...
>>>> };
>>>>
>>>>
>>>> Let me know if some other approach needs to be taken into account in
>>>> at24 driver for this to work.
>>>>
>>>> Thank you,
>>>> Claudiu Beznea
>>>>
>>>
>>> Hi Claudiu,
>>>
>>> First of all: any new compatibles need to go into the DT bindings document.
>>
>> Agree! I missed this.
>>
>>>
>>>
>>>>  drivers/misc/eeprom/at24.c | 69 ++++++++++++++++++++++----------------
>>>>  1 file changed, 40 insertions(+), 29 deletions(-)
>>>>
>>>> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
>>>> index 926408b41270..ae2fbcb5e83d 100644
>>>> --- a/drivers/misc/eeprom/at24.c
>>>> +++ b/drivers/misc/eeprom/at24.c
>>>> @@ -123,17 +123,19 @@ MODULE_PARM_DESC(at24_write_timeout, "Time (in ms) to try writes (default 25)");
>>>>  struct at24_chip_data {
>>>>         u32 byte_len;
>>>>         u8 flags;
>>>> +       u8 adjoff;
>>>>         void (*read_post)(unsigned int off, char *buf, size_t count);
>>>>  };
>>>>
>>>> -#define AT24_CHIP_DATA(_name, _len, _flags)                            \
>>>> +#define AT24_CHIP_DATA(_name, _len, _flags, _adjoff)                   \
>>>>         static const struct at24_chip_data _name = {                    \
>>>> -               .byte_len = _len, .flags = _flags,                      \
>>>> +               .byte_len = _len, .flags = _flags, .adjoff = _adjoff, \
>>>>         }
>>>>
>>>> -#define AT24_CHIP_DATA_CB(_name, _len, _flags, _read_post)             \
>>>> +#define AT24_CHIP_DATA_CB(_name, _len, _flags, _adjoff, _read_post)    \
>>>>         static const struct at24_chip_data _name = {                    \
>>>>                 .byte_len = _len, .flags = _flags,                      \
>>>> +               .adjoff = _adjoff,                                      \
>>>>                 .read_post = _read_post,                                \
>>>>         }
>>>>
>>>> @@ -158,48 +160,52 @@ static void at24_read_post_vaio(unsigned int off, char *buf, size_t count)
>>>>  }
>>>>
>>>>  /* needs 8 addresses as A0-A2 are ignored */
>>>> -AT24_CHIP_DATA(at24_data_24c00, 128 / 8, AT24_FLAG_TAKE8ADDR);
>>>> +AT24_CHIP_DATA(at24_data_24c00, 128 / 8, AT24_FLAG_TAKE8ADDR, 0);
>>>>  /* old variants can't be handled with this generic entry! */
>>>> -AT24_CHIP_DATA(at24_data_24c01, 1024 / 8, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c01, 1024 / 8, 0, 0);
>>>>  AT24_CHIP_DATA(at24_data_24cs01, 16,
>>>> -       AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
>>>> -AT24_CHIP_DATA(at24_data_24c02, 2048 / 8, 0);
>>>> +       AT24_FLAG_SERIAL | AT24_FLAG_READONLY, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c02, 2048 / 8, 0, 0);
>>>>  AT24_CHIP_DATA(at24_data_24cs02, 16,
>>>> -       AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
>>>> +       AT24_FLAG_SERIAL | AT24_FLAG_READONLY, 0);
>>>>  AT24_CHIP_DATA(at24_data_24mac402, 48 / 8,
>>>> -       AT24_FLAG_MAC | AT24_FLAG_READONLY);
>>>> +       AT24_FLAG_MAC | AT24_FLAG_READONLY, 1);
>>>>  AT24_CHIP_DATA(at24_data_24mac602, 64 / 8,
>>>> -       AT24_FLAG_MAC | AT24_FLAG_READONLY);
>>>> +       AT24_FLAG_MAC | AT24_FLAG_READONLY, 1);
>>>> +AT24_CHIP_DATA(at24_data_24mac02e4, 48 / 8,
>>>> +       AT24_FLAG_MAC | AT24_FLAG_READONLY, 0);
>>>> +AT24_CHIP_DATA(at24_data_24mac02e6, 64 / 8,
>>>> +       AT24_FLAG_MAC | AT24_FLAG_READONLY, 0);
>>>>  /* spd is a 24c02 in memory DIMMs */
>>>>  AT24_CHIP_DATA(at24_data_spd, 2048 / 8,
>>>> -       AT24_FLAG_READONLY | AT24_FLAG_IRUGO);
>>>> +       AT24_FLAG_READONLY | AT24_FLAG_IRUGO, 0);
>>>>  /* 24c02_vaio is a 24c02 on some Sony laptops */
>>>>  AT24_CHIP_DATA_CB(at24_data_24c02_vaio, 2048 / 8,
>>>> -       AT24_FLAG_READONLY | AT24_FLAG_IRUGO,
>>>> +       AT24_FLAG_READONLY | AT24_FLAG_IRUGO, 0,
>>>>         at24_read_post_vaio);
>>>> -AT24_CHIP_DATA(at24_data_24c04, 4096 / 8, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c04, 4096 / 8, 0, 0);
>>>>  AT24_CHIP_DATA(at24_data_24cs04, 16,
>>>> -       AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
>>>> +       AT24_FLAG_SERIAL | AT24_FLAG_READONLY, 0);
>>>>  /* 24rf08 quirk is handled at i2c-core */
>>>> -AT24_CHIP_DATA(at24_data_24c08, 8192 / 8, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c08, 8192 / 8, 0, 0);
>>>>  AT24_CHIP_DATA(at24_data_24cs08, 16,
>>>> -       AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
>>>> -AT24_CHIP_DATA(at24_data_24c16, 16384 / 8, 0);
>>>> +       AT24_FLAG_SERIAL | AT24_FLAG_READONLY, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c16, 16384 / 8, 0, 0);
>>>>  AT24_CHIP_DATA(at24_data_24cs16, 16,
>>>> -       AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
>>>> -AT24_CHIP_DATA(at24_data_24c32, 32768 / 8, AT24_FLAG_ADDR16);
>>>> +       AT24_FLAG_SERIAL | AT24_FLAG_READONLY, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c32, 32768 / 8, AT24_FLAG_ADDR16, 0);
>>>>  AT24_CHIP_DATA(at24_data_24cs32, 16,
>>>> -       AT24_FLAG_ADDR16 | AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
>>>> -AT24_CHIP_DATA(at24_data_24c64, 65536 / 8, AT24_FLAG_ADDR16);
>>>> +       AT24_FLAG_ADDR16 | AT24_FLAG_SERIAL | AT24_FLAG_READONLY, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c64, 65536 / 8, AT24_FLAG_ADDR16, 0);
>>>>  AT24_CHIP_DATA(at24_data_24cs64, 16,
>>>> -       AT24_FLAG_ADDR16 | AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
>>>> -AT24_CHIP_DATA(at24_data_24c128, 131072 / 8, AT24_FLAG_ADDR16);
>>>> -AT24_CHIP_DATA(at24_data_24c256, 262144 / 8, AT24_FLAG_ADDR16);
>>>> -AT24_CHIP_DATA(at24_data_24c512, 524288 / 8, AT24_FLAG_ADDR16);
>>>> -AT24_CHIP_DATA(at24_data_24c1024, 1048576 / 8, AT24_FLAG_ADDR16);
>>>> -AT24_CHIP_DATA(at24_data_24c2048, 2097152 / 8, AT24_FLAG_ADDR16);
>>>> +       AT24_FLAG_ADDR16 | AT24_FLAG_SERIAL | AT24_FLAG_READONLY, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c128, 131072 / 8, AT24_FLAG_ADDR16, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c256, 262144 / 8, AT24_FLAG_ADDR16, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c512, 524288 / 8, AT24_FLAG_ADDR16, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c1024, 1048576 / 8, AT24_FLAG_ADDR16, 0);
>>>> +AT24_CHIP_DATA(at24_data_24c2048, 2097152 / 8, AT24_FLAG_ADDR16, 0);
>>>>  /* identical to 24c08 ? */
>>>> -AT24_CHIP_DATA(at24_data_INT3499, 8192 / 8, 0);
>>>> +AT24_CHIP_DATA(at24_data_INT3499, 8192 / 8, 0, 0);
>>>>
>>>>  static const struct i2c_device_id at24_ids[] = {
>>>>         { "24c00",      (kernel_ulong_t)&at24_data_24c00 },
>>>> @@ -208,7 +214,9 @@ static const struct i2c_device_id at24_ids[] = {
>>>>         { "24c02",      (kernel_ulong_t)&at24_data_24c02 },
>>>>         { "24cs02",     (kernel_ulong_t)&at24_data_24cs02 },
>>>>         { "24mac402",   (kernel_ulong_t)&at24_data_24mac402 },
>>>> +       { "24mac02e4",  (kernel_ulong_t)&at24_data_24mac02e4 },
>>>>         { "24mac602",   (kernel_ulong_t)&at24_data_24mac602 },
>>>> +       { "24mac02e6",  (kernel_ulong_t)&at24_data_24mac02e6 },
>>>>         { "spd",        (kernel_ulong_t)&at24_data_spd },
>>>>         { "24c02-vaio", (kernel_ulong_t)&at24_data_24c02_vaio },
>>>>         { "24c04",      (kernel_ulong_t)&at24_data_24c04 },
>>>> @@ -238,7 +246,9 @@ static const struct of_device_id at24_of_match[] = {
>>>>         { .compatible = "atmel,24c02",          .data = &at24_data_24c02 },
>>>>         { .compatible = "atmel,24cs02",         .data = &at24_data_24cs02 },
>>>>         { .compatible = "atmel,24mac402",       .data = &at24_data_24mac402 },
>>>> +       { .compatible = "atmel,24mac02e4",      .data = &at24_data_24mac02e4 },
>>>>         { .compatible = "atmel,24mac602",       .data = &at24_data_24mac602 },
>>>> +       { .compatible = "atmel,24mac02e6",      .data = &at24_data_24mac02e6 },
>>>>         { .compatible = "atmel,spd",            .data = &at24_data_spd },
>>>>         { .compatible = "atmel,24c04",          .data = &at24_data_24c04 },
>>>>         { .compatible = "atmel,24cs04",         .data = &at24_data_24cs04 },
>>>> @@ -690,7 +700,8 @@ static int at24_probe(struct i2c_client *client)
>>>>         at24->flags = flags;
>>>>         at24->read_post = cdata->read_post;
>>>>         at24->num_addresses = num_addresses;
>>>> -       at24->offset_adj = at24_get_offset_adj(flags, byte_len);
>>>> +       at24->offset_adj = cdata->adjoff ?
>>>> +                               at24_get_offset_adj(flags, byte_len) : 0;
>>>>         at24->client[0].client = client;
>>>>         at24->client[0].regmap = regmap;
>>>>
>>>> --
>>>> 2.25.1
>>>>
>>>
>>> What is the problem you're trying to solve?
>>
>> I wanted to instantiate a NVMEM cell with proper offset and size via DT and
>> make whatever Ethernet driver aware of this NVMEM cell via DT bindings, as
>> bellow:
>>
>> &i2cnode {
>>         // ...
>>         eeprom0: eeprom0@52 {
>>                 compatible = "atmel,24mac02e4";
>>                 #address-cells = <1>;
>>                 #size-cells = <0>;
>>                 reg = <0x52>;
>>                 pagesize = <16>;
>>                 size = <256>;
>>                 status = "okay";
>>
>>                 eeprom0_eui48: eui48@fa {
>>                         reg = <0xfa 0x6>;
>>                 };
>>         };
>> };
>>
>> &gmac {
>>         // ...
>>
>>         nvmem-cells = <&eeprom0_eui48>;
>>         nvmem-cell-names = "mac-address";
>>
>>         // ...
>> };
>>
>> By adding this new compatible and changing the driver to not adjust the
>> NVMEM cell offset for it but make it use the one provided in DT I was
>> thinking this may scale for any future EEPROM storing MAC addresses at any
>> offsets (because these would be provided via DT and not adjusted by driver).
>>
>> I the current at24 driver I haven't managed to find a compatible in the
>> driver that mach the offset 0xfa (used to store MAC address on case of
>> 24AA025E48).
>>
>>> The MAC area is accessible
>>> on a different device address. The variants with serial and MAC areas
>>> are meant to be instantiated as devices separate from the main
>>> writeable area and you can then create an nvmem cell that will take up
>>> the whole MAC.
>>>
>>> Or does your model keep the MAC in the same block that's used for
>>> writing? In which case just using a regular compatible that matches
>>> the size and creating the nvmem cell at the right offset should be
>>> enough, right?
>>
>> Meaning describing the NVMEM cell in DT with an offset such that the driver
>> adjustment +/- that offset to lead to the offset described in EEPROM datasheet?
>>
>>>
>>> Am I missing something?
>>
>>
>>
>>>
>>> Bartosz
>>>
>>