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

From: Bartosz Golaszewski
Date: Mon Apr 12 2021 - 14:29:32 EST

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On Mon, Apr 12, 2021 at 9:42 AM <Claudiu.Beznea@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> >> ---
> >>
> >> 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.

>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?

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
> >
>

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In reply to: Claudiu.Beznea: "Re: [PATCH] eeprom: at24: avoid adjusting offset for 24AA025E{48, 64}"
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