lkml.org 
[lkml]   [2012]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH v3.4-rc3] MTD: NAND: ams-delta: Fix request_mem_region() failure
Date
Dnia środa, 25 kwietnia 2012 18:13:38 Artem Bityutskiy pisze:
> On Tue, 2012-04-17 at 15:49 +0200, Janusz Krzysztofik wrote:
> > A call to request_mem_region() has been introduced in the omap-gpio
> > driver recently (commit 96751fcbe5438e95514b025e9cee7a6d38038f40,
> > "gpio/omap: Use devm_ API and add request_mem_region"). This change
> > prevented the Amstrad Delta NAND driver, which was doing the same in
> > order to take control over OMAP MPU I/O lines that the NAND device
hangs
> > off, from loading successfully.
> >
> > There is another driver, omap-keypad, which also manipulates OMAP
MPUIO
> > registers, but has never been calling request_mem_region() on
startup,
> > so it's not affected by the change in the gpio-omap and works
correctly.
> >
> > Drop request_mem_region() call and related bits from ams-delta NAND
> > driver.
> >
> > Created and tested against linux-3.4-rc3.
> >
> > Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
>
> How about race conditions? Where is the guarantee that these 2 drivers
> won't affect each other when doing I/O at the same time to the same HW
> resources?

Both drivers use separate subsets of registers that belong to the OMAP1
MPU I/O device, but are used for controlling different sets of I/O pins.
The NAND driver reads/writes the folowing registers:
- OMAP_MPUIO_INPUT_LATCH,
- OMAP_MPUIO_OUTPUT,
- OMAP_MPUIO_IO_CNTL,
while the keypad driver - the following:
- OMAP_MPUIO_KBR_LATCH,
- OMAP_MPUIO_KBC,
- OMAP_MPUIO_KBD_MASKIT
- OMAP_MPUIO_GPIO_DEBOUNCING.
Both subsets are non-overlapping, and we rely on the drivers being free
of bugs and doing their job correctly, not stepping on each others'
feet, I guess.

Thanks,
Janusz
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2012-04-25 19:19    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site