From: Anton Vorontsov <avorontsov@ru.mvista.com>
To: Laurent Pinchart <laurentp@cse-semaphore.com>
Cc: linuxppc-dev@ozlabs.org, Greg Kroah-Hartman <greg@kroah.com>,
linux-usb@vger.kernel.org,
David Brownell <dbrownell@users.sourceforge.net>,
Li Yang <leoli@freescale.com>,
linux-kernel@vger.kernel.org, Timur Tabi <timur@freescale.com>
Subject: Re: [PATCH 1/3] gpiolib: make gpio_to_chip() public
Date: Mon, 18 Aug 2008 18:33:43 +0400 [thread overview]
Message-ID: <20080818143343.GA30812@oksana.dev.rtsoft.ru> (raw)
In-Reply-To: <200808181558.50182.laurentp@cse-semaphore.com>
On Mon, Aug 18, 2008 at 03:58:46PM +0200, Laurent Pinchart wrote:
[...]
> > Not exactly. But you can do this way, if you need to preserve
> > a direction. What I did is a bit different though.
> >
> > qe_gpio_set_dedicated() actually just restores a mode that
> > firmware had set up, including direction (since direction could
> > be a part of dedicated configuration).
> >
> > That is, upon GPIO controller registration, we save all registers,
> > then driver can set up a pin to a GPIO mode via standard API, and
> > then it can _revert_ a pin to a dedicated function via
> > qe_gpio_set_dedicated() call. Dedicated function is specified by
> > the firmware (or board file), we're just restoring it.
>
> The semantic of the set_dedicated() operation needs to be clearly
> defined then.
It is. We set up a dedicated function that firmware (or board file)
has configured.
> I can live with this behaviour, but it might not be
> acceptable for everybody.
For example?
> Your patch requires the firmware to set a pin in dedicated mode at
> bootup in order to be used later in dedicated mode.
Yes. On a PowerPC this is always true: firmware should set up PIO
config. Linux' board file could fixup the firmware though.
Another option would be to add some argument to the set_dedicated
call, thus the software could specify arbitrary dedicated
function (thus no need to save/restore anything). But this would
be SOC-model specific, thus no driver can use this argument anyway.
> If, for some
> reason (driver not loaded, ...), no GPIO user shows up for that
> pin, it will stay configured in dedicated mode.
Yes.
> It might be better to set the PAR bit unconditionally in
Why it might be better? That way you may set up wrong _GPIO_
mode, because you didn't set PAR bit (when PAR bit set
DIR/ODR/DAT bits are losing their meanings).
> qe_gpio_set_dedicated() instead of restoring its value. That way
> the board initialization code could just set the DIR, DAT and ODR
> bits for dedicated mode but still configure the pin in GPIO mode.
--
Anton Vorontsov
email: cbouatmailru@gmail.com
irc://irc.freenode.net/bd2
next prev parent reply other threads:[~2008-08-18 14:33 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-08 16:17 [PATCH 0/3] Patches to support QE USB Host Controller Anton Vorontsov
2008-08-08 16:18 ` [PATCH 1/3] gpiolib: make gpio_to_chip() public Anton Vorontsov
2008-08-14 14:04 ` Laurent Pinchart
2008-08-14 14:14 ` Anton Vorontsov
2008-08-14 14:45 ` Laurent Pinchart
2008-08-14 15:10 ` Anton Vorontsov
2008-08-18 13:58 ` Laurent Pinchart
2008-08-18 14:33 ` Anton Vorontsov [this message]
2008-08-18 14:44 ` Laurent Pinchart
2008-08-18 15:33 ` Anton Vorontsov
2008-08-19 9:26 ` Laurent Pinchart
2008-08-19 14:50 ` Anton Vorontsov
2008-08-08 16:18 ` [PATCH 2/3] powerpc/qe: new call to revert a gpio to a dedicated function Anton Vorontsov
2008-08-08 16:18 ` [PATCH 3/3] USB: driver for Freescale QUICC Engine USB Host Controller Anton Vorontsov
2008-08-08 23:26 ` [PATCH 0/3] Patches to support QE " Greg KH
2008-08-26 15:49 ` Anton Vorontsov
2008-08-14 12:15 ` Laurent Pinchart
2008-09-24 20:04 ` David Brownell
2008-09-18 15:16 Anton Vorontsov
2008-09-18 15:17 ` [PATCH 1/3] gpiolib: make gpio_to_chip() public Anton Vorontsov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20080818143343.GA30812@oksana.dev.rtsoft.ru \
--to=avorontsov@ru.mvista.com \
--cc=dbrownell@users.sourceforge.net \
--cc=greg@kroah.com \
--cc=laurentp@cse-semaphore.com \
--cc=leoli@freescale.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=linuxppc-dev@ozlabs.org \
--cc=timur@freescale.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).