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SubjectRe: [PATCH 3/4] arm: am33xx: DT quirks for am33xx based beaglebone variants
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Hi Tony,

> On Feb 19, 2015, at 20:16 , Tony Lindgren <tony@atomide.com> wrote:
>
> * Pantelis Antoniou <pantelis.antoniou@konsulko.com> [150218 07:03]:
>> Implement DT quirks for the am33xx beaglebone boards.
>> --- /dev/null
>> +++ b/arch/arm/mach-omap2/am33xx-dt-quirks.c
> ...
>> +
>> +/*
>> + * The board IDs for am33xx board are in an I2C EEPROM
>> + * We are very early in the boot process so we have to
>> + * read the EEPROM directly without using the I2C layer.
>> + *
>> + * Note that we rely on the bootloader setting up the muxes
>> + * (which is the case for u-boot).
>> + */
>> +
>> +/* I2C Status Register (OMAP_I2C_STAT): */
>> +#define OMAP_I2C_STAT_XDR (1 << 14) /* TX Buffer draining */
>> +#define OMAP_I2C_STAT_RDR (1 << 13) /* RX Buffer draining */
>> +#define OMAP_I2C_STAT_BB (1 << 12) /* Bus busy */
>> +#define OMAP_I2C_STAT_ROVR (1 << 11) /* Receive overrun */
>> +#define OMAP_I2C_STAT_XUDF (1 << 10) /* Transmit underflow */
>> +#define OMAP_I2C_STAT_AAS (1 << 9) /* Address as slave */
>> +#define OMAP_I2C_STAT_BF (1 << 8) /* Bus Free */
>> +#define OMAP_I2C_STAT_XRDY (1 << 4) /* Transmit data ready */
>> +#define OMAP_I2C_STAT_RRDY (1 << 3) /* Receive data ready */
>> +#define OMAP_I2C_STAT_ARDY (1 << 2) /* Register access ready */
>> +#define OMAP_I2C_STAT_NACK (1 << 1) /* No ack interrupt enable */
>> +#define OMAP_I2C_STAT_AL (1 << 0) /* Arbitration lost int ena */
> ...
>
> Uhh I don't like the idea of duplicating the i2c-omap.c driver under
> arch/arm.. And in general we should initialize things later rather
> than earlier.
>
> What's stopping doing these quirk checks later on time with just
> a regular device driver, something like drivers/misc/bbone-quirks.c?
>

We have no choice; we are way early in the boot process, right after
the device tree unflattening step.

I’ve toyed with the idea of using early platform devices but the omap-i2c driver
would need some tender love and care to make it work, and I didn’t want to get
bogged down with i2c driver details at this point.

> Regards,
>
> Tony

Regards

— Pantelis



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