From: Alan Cox <alan@linux.intel.com>
To: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: gregkh@suse.de, linux-kernel@vger.kernel.org,
linux-serial@vger.kernel.org, scottwood@freescale.com,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 3/3] 8250: add workaround for MPC8[356]xx UART break IRQ storm
Date: Fri, 2 Dec 2011 00:57:52 +0000 [thread overview]
Message-ID: <20111202005752.10ce5eea@bob.linux.org.uk> (raw)
In-Reply-To: <1322783258-20443-4-git-send-email-paul.gortmaker@windriver.com>
> @@ -1553,7 +1554,15 @@ static void serial8250_handle_port(struct
> uart_8250_port *up)
> spin_lock_irqsave(&up->port.lock, flags);
>
> - status = serial_inp(up, UART_LSR);
> + /* Workaround for IRQ storm errata on break with Freescale
> 16550 */
> + if (UART_BUG_FSLBK & up->port.bugs && up->lsr_last &
> UART_LSR_BI) {
> + up->lsr_last &= ~UART_LSR_BI;
> + serial_inp(up, UART_RX);
> + spin_unlock_irqrestore(&up->port.lock, flags);
> + return;
> + }
> +
> + status = up->lsr_last = serial_inp(up, UART_LSR);
We've now had a recent pile of IRQ function changes adding more quirk
bits and special casing. This doesn't scale. We either need to make
handle_port a method the specific drivers can override or you could
hide the mess in your serial_inp implementation and not touch any core
code.
I really don't mind which but I suspect dealing with it in your
serial_inp handler so that when you read UART_LSR you do the fixup
might be simplest providing you can just do that.
Sorting out a ->handle_port override is probably ultimately the right
thing to do and then we can push some of the other funnies out further.
At this point it's becoming increasingly clear that 8250 UART cloners
are both very bad at cloning the things accurately, and very busy adding
extra useful features so we need to start to treat 8250.c as a library
you can wrap.
Alan
next prev parent reply other threads:[~2011-12-02 0:55 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-01 23:47 [PATCH 0/3] RFC Fix Fsl 8250 BRK bug via letting plat code set bugs Paul Gortmaker
2011-12-01 23:47 ` [PATCH 1/3] serial: make bugs field not specific to 8250 type uarts Paul Gortmaker
2011-12-02 0:51 ` Alan Cox
2011-12-02 1:32 ` Paul Gortmaker
2011-12-02 11:49 ` Alan Cox
2011-12-01 23:47 ` [PATCH 2/3] serial: allow passing in hardware bug info via platform device Paul Gortmaker
2011-12-01 23:47 ` [PATCH 3/3] 8250: add workaround for MPC8[356]xx UART break IRQ storm Paul Gortmaker
2011-12-01 23:51 ` Scott Wood
2011-12-02 0:05 ` Paul Gortmaker
2011-12-02 0:17 ` Kumar Gala
2011-12-02 11:30 ` Alan Cox
2011-12-02 16:34 ` Paul Gortmaker
2011-12-02 17:27 ` Scott Wood
2011-12-02 0:57 ` Alan Cox [this message]
2011-12-02 1:42 ` Paul Gortmaker
2011-12-04 23:42 ` [PATCH 0/6] RFCv2 Fix Fsl 8250 BRK bug Paul Gortmaker
2011-12-04 23:42 ` [PATCH 1/6] serial: move struct uart_8250_port from 8250.c to 8250.h Paul Gortmaker
2011-12-04 23:42 ` [PATCH 2/6] serial: clean up parameter passing for 8250 Rx IRQ handling Paul Gortmaker
2011-12-04 23:42 ` [PATCH 3/6] serial: export the key functions for an 8250 IRQ handler Paul Gortmaker
2011-12-04 23:42 ` [PATCH 4/6] serial: make 8250 timeout use the specified " Paul Gortmaker
2011-12-04 23:42 ` [PATCH 5/6] serial: manually inline serial8250_handle_port Paul Gortmaker
2011-12-04 23:42 ` [PATCH 6/6] serial: add irq handler for Freescale 16550 errata Paul Gortmaker
2011-12-05 12:18 ` [PATCH 0/6] RFCv2 Fix Fsl 8250 BRK bug Alan Cox
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