[gta02-core] Wasting valuable pins (Was: PMU cleanup)

Rask Ingemann Lambertsen ccc94453 at vip.cybercity.dk
Tue Aug 25 11:37:40 CEST 2009

On Wed, Aug 19, 2009 at 03:24:53PM -0300, Werner Almesberger wrote:
> ?lvaro Lopes wrote:
> > * nGSM_OC is not used any more ? It was connected to EINT19, but due to
> > ECN0001, we are using this GPIO for board revision check. What was the
> > purpose of this signal ?
> Hmm, that change doesn't look so good. Spending EINTs on the board
> revision sounds like a horrible waste to me.

   I agree, and we have more cases where pins with relatively valueable
special functions are used for simple GPIO when less valueable pins could
have been used instead. Other such examples are the DMA interface and the
camera port. We've had no GPIO allocation strategy to inherit from the GTA02
and now that the abundance of unused GPIO on the LCD interface has gone,
we're beginning to suffer from it.

> (Ah, another task for the MPU: record the board revision :)

   Or we could have a serial/I2C EEPROM. It would allow much more fine
grained board revision information, and as hardware fixed are applied (or
hardware bugs are discovered - think bogus GTA02 earpiece capacitors), you
could update the EEPROM to reflect the state of the board.

> So it's not a signal we strictly need. However, since we have it, we
> may as well connect it. If there's modem trouble, it may help to
> rule out some failure scenarios.

   But nGSM_OC is a bit like MODEM_RST and BT_PIO_5: It's allocated to a
GPIO but is not used by the kernel[1] and two years after Neo 1973 release,
still nobody misses it. So I think of losing nGSM_OC as a cleanup, even if
it was probably not intentional. Another signal that can go is nACCEL_CS now
that we have only one accelerometer.

[1] $ grep -E -e 'GTA.*(MODEM_RST|GSM_OC|PIO5)' --recursive *
arch/arm/mach-s3c2410/include/mach/gta01.h:#define GTA01_GPIO_MODEM_RST	S3C2410_GPB6
arch/arm/mach-s3c2442/include/mach/gta02.h:#define GTA02_GPIO_MODEM_RST	S3C2410_GPB5
arch/arm/mach-s3c2442/include/mach/gta02.h:#define GTA02_GPIO_PIO5		S3C2410_GPC5	/* v3 + v4 only */
arch/arm/mach-s3c2442/include/mach/gta02.h:#define GTA02v3_GPIO_nGSM_OC	S3C2410_GPG11	/* v3 + v4 only */
arch/arm/mach-s3c2442/include/mach/gta02.h:#define GTA02v3_IRQ_nGSM_OC	IRQ_EINT19	/* v3 + v4 only */

Rask Ingemann Lambertsen
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