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Re: [PATCH] serial_txx9: forcibly init the spinlock for PCI UART used as

To: Russell King <rmk@arm.linux.org.uk>
Subject: Re: [PATCH] serial_txx9: forcibly init the spinlock for PCI UART used as a console
From: Sergei Shtylyov <sshtylyov@dev.rtsoft.ru>
Date: Tue, 27 Dec 2005 22:31:53 +0300
Cc: Atsushi Nemoto <anemo@mba.ocn.ne.jp>, linux-mips@linux-mips.org, ralf@linux-mips.org
In-reply-to: <43B18DD2.3090206@ru.mvista.com>
Organization: RTSoft, Inc.
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References: <43B06DB4.409@ru.mvista.com> <20051227.144551.79070832.nemoto@toshiba-tops.co.jp> <43B143EE.6070700@ru.mvista.com> <20051228.003457.74752441.anemo@mba.ocn.ne.jp> <20051227184152.GA4474@flint.arm.linux.org.uk> <43B18DD2.3090206@ru.mvista.com>
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Hello.

Sergei Shtylylov wrote:

no need to pre-register all the uart ports at driver initialisation
time.  Consequently, there's no need to remove them all when you
remove the module.

Hm, then the driver would need to keep track of which ports it has registered and which it has not...

   However, it does this already in a way, via port type.

 > Secondly, the upshot of this is that you only call uart_add_one_port()
 > when you initialise a PCI card.

Not the case as I've said; uart_add_one_port() should be called on driver startup anyway...

This should result in a cleaner implementation, and the console will
not be started until you detect the PCI card.

It will still be started with the console_initcall() in this driver, if that code is not also deleted...

That doesn't matter. Driver init time uart_add_one_port() calls to register SOC UARTs will result in register_console() being called multiple times unsuccesfully anyway before we get to the PCI UART to which the console is assigned. All in all, the problem of uninit'ed PCI port spinlock will remain unless serial core is fixed (ot at least the driver). Proposed driver re-design wouldn't help as this is actually chicken-before-egg type problem -- uart_add_one_port() assumes that the console is setup beforehand, and this just can't happen in case of a PCI card.

WBR, Sergei

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