[PATCH u-boot-marvell 2/3] arm: mvebu: turris_omnia: Use the i2c_eeprom misc driver for EEPROM reading in U-Boot proper

[Marek Behún]

On Tue, Sep 03, 2024 at 08:57:24AM +0200, Stefan Roese wrote:
> On 8/29/24 10:08, Marek Behún wrote:
> > Use the i2c_eeprom miscellaneous driver for reading Turris Omnia EEPROM
> > in U-Boot proper. Keep using dm_i2c_read() in SPL build, since adding
> > the i2c_eeprom driver to SPL build increases the image by 1.5 KiB.
> > 
> > Signed-off-by: Marek Behún <kabel at kernel.org>
> > ---
> >   arch/arm/mach-mvebu/Kconfig              | 1 +
> >   board/CZ.NIC/turris_omnia/turris_omnia.c | 9 +++++++--
> >   configs/turris_omnia_defconfig           | 1 -
> >   3 files changed, 8 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/arm/mach-mvebu/Kconfig b/arch/arm/mach-mvebu/Kconfig
> > index 4a8328760eb..c1a1a333e6c 100644
> > --- a/arch/arm/mach-mvebu/Kconfig
> > +++ b/arch/arm/mach-mvebu/Kconfig
> > @@ -149,6 +149,7 @@ config TARGET_TURRIS_OMNIA
> >   	select SPL_SYS_MALLOC_SIMPLE
> >   	select SYS_I2C_MVTWSI
> >   	select ATSHA204A
> > +	select I2C_EEPROM
> >   	select ARMADA_38X_SUPPORT_OLD_DDR3_TRAINING
> >   config TARGET_TURRIS_MOX
> > diff --git a/board/CZ.NIC/turris_omnia/turris_omnia.c b/board/CZ.NIC/turris_omnia/turris_omnia.c
> > index 392df53a6d8..46f20f05c05 100644
> > --- a/board/CZ.NIC/turris_omnia/turris_omnia.c
> > +++ b/board/CZ.NIC/turris_omnia/turris_omnia.c
> > @@ -23,6 +23,7 @@
> >   #include <dt-bindings/gpio/gpio.h>
> >   #include <fdt_support.h>
> >   #include <hexdump.h>
> > +#include <i2c_eeprom.h>
> >   #include <time.h>
> >   #include <turris-omnia-mcu-interface.h>
> >   #include <linux/bitops.h>
> > @@ -473,9 +474,13 @@ static bool omnia_read_eeprom(struct omnia_eeprom *oep)
> >   	if (!eeprom)
> >   		return false;
> > -	ret = dm_i2c_read(eeprom, 0, (void *)oep, sizeof(*oep));
> > +	if (IS_ENABLED(CONFIG_SPL_BUILD))
> > +		ret = dm_i2c_read(eeprom, 0, (void *)oep, sizeof(*oep));
> > +	else
> > +		ret = i2c_eeprom_read(eeprom, 0, (void *)oep, sizeof(*oep));
> 
> So whats the advantage using i2c_eeprom_read() here in U-Boot proper?
> The only thing that stands out to me is that the code get more complex
> because of the SPL/non-SPL distinction.

The reasons are as follows:
- it's "more correct" semantically

- the i2c_eeprom driver was already enabled for U-Boot proper in
  defconfig (with this commit selected by the board), because of the
  `eeprom` commmand, so I thought "why not use it?"
  (looking at the code now, it goes
     i2c_eeprom_read()
       dereference of i2c_eeprom_ops->read method
       i2c_eeprom_std_read()
         dm_i2c_read()
   so the complication is trivial, IMO)

- the following commit adds code that writes the eeprom, and this cannot
  be done with simple dm_i2c_write(), because each eeprom page has to be
  written by another transaction, which is what i2c_eeprom_write()
  does.

  So I knew that I was going to add i2c_eeprom_write(), and I thought
  that it would seem weird writing with i2c_eeprom_write() but reading
  with dm_i2c_read().

Marek