Subject: [PATCH v5 02/11] drivers: PL011: refactor pl011_startup()

From: [email-masked] (Andre Przywara)
Date: Fri, 25 Sep 2015 16:21:48 +0100

Hi Timur,

On 25/09/15 00:11, Timur Tabi wrote:
> On Thu, May 21, 2015 at 11:26 AM, Andre Przywara <[email-masked]> wrote:
>> +static void pl011_enable_interrupts(struct uart_amba_port *uap)
>> +{
>> +       spin_lock_irq(&uap->port.lock);
>> +
>> +       /* Clear out any spuriously appearing RX interrupts */
>> +       writew(UART011_RTIS | UART011_RXIS,
>> +              uap->port.membase + UART011_ICR);
>> +       uap->im = UART011_RTIM;
>> +       if (!pl011_dma_rx_running(uap))
>> +               uap->im |= UART011_RXIM;
>> +       writew(uap->im, uap->port.membase + UART011_IMSC);
>> +       spin_unlock_irq(&uap->port.lock);
>> +}
> 
> Shouldn't this function be using spin_lock_irqsave() and
> spin_unlock_irqrestore()?  If interrupts are generally disabled before
> calling this function, then they will be enabled by the
> spin_unlock_irq() call, and I don't think we want that.  This function
> is only supposed to enable pl011 interrupts, not all interrupts.

Are you seeing an actual issue with this? Does changing it fix anything?
Looking at the history I see that these locks predate git history.
If I get this correctly, going from spin_{un,}lock_irq to the _irqsave
variants should always be safe, but I'd like to hear more opinions on this.

Cheers,
Andre.