linux-kernel - Re: [PATCH] tty: add Moxa Smartio MUE serial driver

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Message-ID: <20160203185008.GA16942@gmail.com>
Date:	Wed, 3 Feb 2016 19:50:08 +0100
From:	Mathieu OTHACEHE <m.othacehe@...il.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc:	gregkh@...uxfoundation.org, jslaby@...e.com,
	akpm@...ux-foundation.org, davem@...emloft.net,
	mchehab@....samsung.com, kvalo@...eaurora.org, joe@...ches.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty: add Moxa Smartio MUE serial driver

Thank you for your comments. I'll come up with v2 soon but, I have
a question about this point :

> > +		/* clear Rx/Tx FIFO's */
> > +		for (i = 0; i < reset_cnt; i++) {
> > +			iowrite8((UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT),
> > +				 info->ioaddr + UART_FCR);
> > +			msleep(sleep_interval);
> 
> No can do - you have a spinlock held while you are tring to sleep. I'm
> not btw clear that you actually need the lock. The tty_port layer ensures
> activate/shutdown don't cross or get duplicated. The only protection you
> might need is versus interrupts, and in that case you could free the IRQ
> up and claim it in activate/shutdown.

So is it possible to replace spin_lock_irqsave/restore by local_irq_save/restore
in activate/shutdown to protect versus interrupts ?

And is it allowed to call msleep while holding local_irq_save ?

Thank you,

Mathieu