From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 07/18] dmaengine/amba-pl08x: Enable/Disable amba_pclk with channel requests
Date: Sun, 31 Jul 2011 18:04:51 +0100 [thread overview]
Message-ID: <20110731170451.GC2975@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAKnu2MppEKxZD2Z77tfShMfG80d-Xx26yBGhZtJkJ2C6SjE=1w@mail.gmail.com>
On Sun, Jul 31, 2011 at 02:04:47AM +0200, Linus Walleij wrote:
> 2011/7/31 Linus Walleij <linus.walleij@linaro.org>:
> > 2011/7/30 Russell King - ARM Linux <linux@arm.linux.org.uk>:
> >> On Sat, Jul 30, 2011 at 01:07:40PM +0100, Russell King - ARM Linux wrote:
> >>> It may make better sense to convert this to runtime PM. ?I suspect
> >>> that there's core support which the amba/bus.c can do to help in that
> >>> respect (eg, managing the apb pclk itself) so that we don't have to
> >>> add the same code to every primecell driver.
> >>
> >> Something like this for the bus driver (untested):
> >>
> >> ?drivers/amba/bus.c | ? 38 ++++++++++++++++++++++++++++++++++++--
> >> ?1 files changed, 36 insertions(+), 2 deletions(-)
> >
> > I think the pm_runtime_* code Rabin put in place inside
> > drivers/spi/spi-pl022.c would play really well with this approach, and
> > just work, so:
> > Acked-by: Linus Walleij <linus.walleij@linaro.org>
>
> ..and while it will just cause some double refcounts on the clock,
> it makes sense to delete the pclk manipulation from the PL022
> driver code as part of the patch, like this:
Yes, this looks fine. Shall I wrap it up as part of my patch?
Two other things I've spotted in this driver are:
1. The remove function doesn't undo what the probe function did to
the pclk and vcore. It needs to keep things balanced. For a driver
which doesn't manage its pclk, this is what happens:
- core gets pclk
- core enables pclk
- core calls driver's probe
- driver sets stuff up
...
- core calls driver's remove
- driver tidies up
- core disables pclk
- core puts pclk
And PL022 does this:
- core gets pclk
- core enables pclk
- core calls driver's probe
- driver sets stuff up
- driver disables pclk
...
- core calls driver's remove
- driver tidies up
- core disables pclk
- core puts pclk
Notice the double-disable of pclk in that sequence. If ->probe disables
pclk, ->remove needs to return with that disable balanced with an enable.
2. It thinks it can refuse 'remove' by returning an error code. This
is false. removes can't be aborted - here's the code from drivers/base/dd.c:
static void __device_release_driver(struct device *dev)
{
...
if (dev->bus && dev->bus->remove)
dev->bus->remove(dev);
else if (drv->remove)
drv->remove(dev);
...
}
Notice how return codes go nowhere. remove should _really_ be a void
function to stop people thinking that it can be aborted. It can't.
next prev parent reply other threads:[~2011-07-31 17:04 UTC|newest]
Thread overview: 102+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-29 10:49 [PATCH 00/18] dmaengine/amba-pl08x updates Viresh Kumar
2011-07-29 10:49 ` [PATCH 01/18] ARM: asm/pl080.h: Protect against multiple inclusion of header file Viresh Kumar
2011-07-30 22:16 ` Linus Walleij
2011-07-29 10:49 ` [PATCH 02/18] dmaengine/amba-pl08x: Resolve formatting issues Viresh Kumar
2011-07-29 11:00 ` Russell King - ARM Linux
2011-07-29 11:21 ` viresh kumar
2011-07-29 12:05 ` Koul, Vinod
2011-07-29 15:25 ` viresh kumar
2011-07-29 10:49 ` [PATCH 03/18] dmaengine/amba-pl08x: Complete doc comment for struct pl08x_txd Viresh Kumar
2011-07-29 10:49 ` [PATCH 04/18] dmaengine/amba-pl08x: Remove redundant comment and rewrite original Viresh Kumar
2011-07-29 12:09 ` Koul, Vinod
2011-07-29 15:47 ` viresh kumar
2011-07-29 16:34 ` Russell King - ARM Linux
2011-07-30 22:32 ` Linus Walleij
2011-07-30 22:57 ` Russell King - ARM Linux
2011-07-30 23:37 ` Linus Walleij
2011-07-31 5:51 ` viresh kumar
2011-07-31 9:06 ` Russell King - ARM Linux
2011-07-29 10:49 ` [PATCH 05/18] dmaengine/amba-pl08x: Changing few prints to dev_dbg from dev_info Viresh Kumar
2011-07-30 22:34 ` Linus Walleij
2011-07-29 10:49 ` [PATCH 06/18] dmaengine/amba-pl08x: Simplify pl08x_ensure_on() Viresh Kumar
2011-07-30 22:36 ` Linus Walleij
2011-07-29 10:49 ` [PATCH 07/18] dmaengine/amba-pl08x: Enable/Disable amba_pclk with channel requests Viresh Kumar
2011-07-30 12:07 ` Russell King - ARM Linux
2011-07-30 13:05 ` Russell King - ARM Linux
2011-07-30 23:53 ` Linus Walleij
2011-07-31 0:04 ` Linus Walleij
2011-07-31 17:04 ` Russell King - ARM Linux [this message]
2011-08-02 9:05 ` Linus Walleij
2011-08-03 12:55 ` Russell King - ARM Linux
2011-08-09 19:50 ` Linus Walleij
2011-07-29 10:49 ` [PATCH 08/18] dmaengine/amba-pl08x: No need to check "ch->signal < 0" Viresh Kumar
2011-07-31 0:09 ` Linus Walleij
2011-07-29 10:49 ` [PATCH 09/18] dmaengine/amba-pl08x: Schedule tasklet in case of error interrupt Viresh Kumar
2011-07-29 12:16 ` Koul, Vinod
2011-07-29 13:02 ` Russell King - ARM Linux
2011-07-29 15:30 ` viresh kumar
2011-08-04 4:25 ` Koul, Vinod
2011-08-04 5:54 ` viresh kumar
2011-08-04 5:32 ` Koul, Vinod
2011-08-14 8:29 ` Russell King - ARM Linux
2011-07-31 0:19 ` Linus Walleij
2011-07-31 5:33 ` viresh kumar
2011-07-29 10:49 ` [PATCH 10/18] dmaengine/amba-pl08x: Get rid of pl08x_pre_boundary() Viresh Kumar
2011-07-29 11:05 ` Russell King - ARM Linux
2011-07-29 12:32 ` Koul, Vinod
2011-07-29 15:58 ` viresh kumar
2011-07-29 12:19 ` Koul, Vinod
2011-07-29 15:40 ` viresh kumar
2011-07-31 0:24 ` Linus Walleij
2011-07-29 10:49 ` [PATCH 11/18] dmaengine/amba-pl08x: max_bytes_per_lli is TRANSFER_SIZE * src_width (not MIN(width)) Viresh Kumar
2011-07-31 0:27 ` Linus Walleij
2011-07-31 9:09 ` Russell King - ARM Linux
2011-07-29 10:49 ` [PATCH 12/18] dmaengine/amba-pl08x: Add prep_single_byte_llis() routine Viresh Kumar
2011-07-29 11:06 ` Russell King - ARM Linux
2011-07-29 11:30 ` viresh kumar
2011-07-29 10:49 ` [PATCH 13/18] dmaengine/amba-pl08x: Align lli_len to max(src.width, dst.width) Viresh Kumar
2011-07-29 12:43 ` Koul, Vinod
2011-07-29 15:39 ` viresh kumar
2011-07-31 0:30 ` Linus Walleij
2011-07-29 10:49 ` [PATCH 14/18] dmaengine/amba-pl08x: Choose peripheral bus as master bus Viresh Kumar
2011-07-31 0:36 ` Linus Walleij
2011-07-29 10:49 ` [PATCH 15/18] dmaengine/amba-pl08x: Pass flow controller information with slave channel data Viresh Kumar
2011-07-29 11:10 ` Russell King - ARM Linux
2011-07-29 11:31 ` viresh kumar
2011-07-31 0:40 ` Linus Walleij
2011-07-31 5:36 ` viresh kumar
2011-07-29 10:49 ` [PATCH 16/18] dmaengine/amba-pl08x: Add support for sg len greater than one for slave transfers Viresh Kumar
2011-07-31 0:41 ` Linus Walleij
2011-08-14 8:36 ` Russell King - ARM Linux
2011-08-15 10:11 ` Linus Walleij
2011-08-18 8:38 ` Viresh Kumar
2011-08-21 8:33 ` Russell King - ARM Linux
2011-08-23 4:22 ` Viresh Kumar
2011-08-23 5:20 ` Koul, Vinod
2011-08-26 3:41 ` Viresh Kumar
2011-08-26 8:03 ` Linus Walleij
2011-08-26 8:51 ` Viresh Kumar
2011-09-01 10:07 ` Viresh Kumar
2011-09-07 18:42 ` Koul, Vinod
2011-09-07 23:01 ` Linus Walleij
2011-09-08 3:50 ` Viresh Kumar
2011-09-08 10:29 ` Linus Walleij
2011-09-08 21:54 ` [PATCH 16/18] dmaengine/ambhe rest oa-pl08x: " Vinod Koul
2011-09-20 6:19 ` Vinod Koul
2011-09-20 6:27 ` Viresh Kumar
2011-09-20 8:08 ` Vinod Koul
2011-07-29 10:49 ` [PATCH 17/18] dmaengine/amba-pl08x: Check txd->llis_va before freeing dma_pool Viresh Kumar
2011-07-31 0:44 ` Linus Walleij
2011-07-29 10:49 ` [PATCH 18/18] dmaengine/amba-pl08x: Call pl08x_free_txd() instead of calling kfree() directly Viresh Kumar
2011-07-29 11:15 ` Russell King - ARM Linux
2011-07-29 11:38 ` viresh kumar
2011-07-31 0:45 ` Linus Walleij
2011-07-31 5:39 ` viresh kumar
2011-07-29 10:57 ` [PATCH 00/18] dmaengine/amba-pl08x updates Russell King - ARM Linux
2011-07-29 11:14 ` viresh kumar
2011-07-29 11:19 ` Russell King - ARM Linux
2011-07-29 11:23 ` viresh kumar
2011-07-29 12:43 ` Russell King - ARM Linux
2011-07-29 15:22 ` viresh kumar
2011-07-29 11:58 ` Koul, Vinod
2011-08-01 5:30 ` viresh kumar
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