linux-kernel - Re: [PATCH 05/15] tty: serial: Add 8250-core based omap driver

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Message-ID: <20140815210716.GE9239@atomide.com>
Date:	Fri, 15 Aug 2014 14:07:16 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	balbi@...com, Vinod Koul <vinod.koul@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 05/15] tty: serial: Add 8250-core based omap driver

* Sebastian Andrzej Siewior <bigeasy@...utronix.de> [140815 10:46]:
> This patch provides a 8250-core based UART driver for the internal OMAP
> UART. The long term goal is to provide the same functionality as the
> current OMAP uart driver and DMA support.
> I tried to merge omap-serial code together with the 8250-core code.
> There should should be hardly a noticable difference. The trigger levels
> are different compared to omap-serial:

Nice, now it mostly works for me with off-idle too :) That is as long
as I have the DMA channels commented out in the .dts file.

And I'm still seeing an occasional hang with pstore console just
showing:

[  289.076538] In-band Error seen by MPU  at address 0
[  289.076538] ------------[ cut here ]------------
[  289.076568] WARNING: CPU: 0 PID: 99 at drivers/bus/omap_l3_smx.c:162 omap3_l3_app_irq+0xdc/0x134()
[  289.076599] Modules linked in:
[  289.076599] CPU: 0 PID: 99 Comm: test-idle-off-8 Tainted: G        W      3.16.0+ #510
[  289.076629] [<c0016c44>] (unwind_backtrace) from [<c00129c8>] (show_stack+0x20/0x24)
[  289.076660] [<c00129c8>] (show_stack) from [<c0714cd4>] (dump_stack+0x88/0xa4)

Which most likely means there's still some glitch with the
runtime PM somewhere and registers are being accessed when
not clocked. I _think_ I did not see it when I did not have
console=ttyS2,115200 in my cmdline but was using just pstore
console.

> The device name is ttyS based instead of ttyO. If a ttyO based node name
> is required please ask udev for it. If both driver are activated (this
> and omap-serial) then this serial driver will take control over the
> device due to the link order

That's still not going to help with the existing kernel cmdlines
and existing installs.. I wonder if we can just do a minimal
dummy serial-omap.c that just proxies all the ttyO read/write
access to ttyS?

Regards,

Tony
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