From: boris.brezillon@free-electrons.com (Boris BREZILLON)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: at91: at91sam9x5: sets NPCS0 (PA14) back to GPIO
Date: Fri, 25 Jul 2014 13:34:26 +0200 [thread overview]
Message-ID: <20140725133426.57f5cf6e@bbrezillon> (raw)
In-Reply-To: <53D23246.1010300@aksignal.cz>
On Fri, 25 Jul 2014 12:32:38 +0200
Ji?? Prchal <jiri.prchal@aksignal.cz> wrote:
>
>
> Dne 25.7.2014 v 12:18 Boris BREZILLON napsal(a):
> >> / # devmem 0xfffff408
> >> 0xF0E04018
> >> / # devmem 0xfffff418
> >> 0xE0C04000
> >> / # devmem 0xfffff438
> >> 0x00C04000
> >> / # devmem 0xfffff43c
> >> 0x13FFD7FB
> >> / # devmem 0xfffff458
> >> 0x00000000
> >> / # devmem 0xfffff468
> >> 0xFF223B4E
> >> / # devmem 0xfffff470
> >> 0x0F000000
> >> / # devmem 0xfffff474
> >> 0x00000000
> >> / # devmem 0xfffff498
> >> 0xFFFFFFFF
> >>
> >> I get thought if is possible that in time of probe fm25 (it's first) is not configured PA14 (it 's last)?
> >
> > Oh, nice catch!
> > I think you've found the origin of this bug.
> > Indeed each device is instantiated sequentially and thus when the first
> > device is probed (CS0) the last one has not requested it's cs_gpio yet
> > (and PA14 is still assigned to periph A).
> >
> > Declaring cs-pins and referencing them in pinctrl-0 solves the issue
> > because in this case all CS pins are requested during controller probe.
> >
> So, what would be the right fix up? I my patch it's not good idea since some other driver can request pin for other
> peripheral earlier than spi. In board dts it could be new investigating for someone else who don't know this issue. I
> think the best way would be request all cs in early spi init since cs depends on each other and must be all of them in
> right state before any communication on bus. They are part of bus, like miso, mosi, clk, not part of chips. Also they
> are defined in parent spi node, not in child chip node.
> Am I right?
Yes, you can take a look at [1] as an example.
[1]http://lxr.free-electrons.com/source/drivers/spi/spi-efm32.c#L361
--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
next prev parent reply other threads:[~2014-07-25 11:34 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-11 10:22 [PATCH] ARM: at91: at91sam9x5: add clocks for usb device Bo Shen
2014-07-11 10:47 ` Alexandre Belloni
2014-07-11 10:55 ` Jiří Prchal
2014-07-24 13:38 ` [PATCH] ARM: at91: at91sam9x5: sets NPCS0 (PA14) back to GPIO Jiří Prchal
2014-07-24 14:26 ` Boris BREZILLON
2014-07-24 15:06 ` Jiří Prchal
2014-07-24 15:58 ` Boris BREZILLON
2014-07-25 6:14 ` Jiří Prchal
2014-07-25 7:53 ` Boris BREZILLON
2014-07-25 8:27 ` Jiří Prchal
2014-07-25 8:45 ` Boris BREZILLON
2014-07-25 8:54 ` Jiří Prchal
2014-07-25 9:01 ` Boris BREZILLON
2014-07-25 9:13 ` Jiří Prchal
2014-07-25 9:31 ` Boris BREZILLON
2014-07-25 10:06 ` Jiří Prchal
2014-07-25 10:18 ` Boris BREZILLON
2014-07-25 10:32 ` Jiří Prchal
2014-07-25 11:34 ` Boris BREZILLON [this message]
2014-07-25 8:33 ` Jiří Prchal
2014-07-25 8:30 ` Alexandre Belloni
2014-07-25 8:36 ` Boris BREZILLON
2014-07-25 8:50 ` Alexandre Belloni
2014-07-25 8:37 ` Jiří Prchal
2014-07-25 8:54 ` Alexandre Belloni
2014-07-25 8:59 ` Jiří Prchal
2014-07-25 9:02 ` Alexandre Belloni
2014-07-25 9:10 ` Boris BREZILLON
2014-07-25 9:40 ` Jiří Prchal
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