Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756073Ab0K3BTg (ORCPT ); Mon, 29 Nov 2010 20:19:36 -0500 Received: from LUNGE.MIT.EDU ([18.54.1.69]:42132 "EHLO lunge.queued.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756057Ab0K3BTf (ORCPT ); Mon, 29 Nov 2010 20:19:35 -0500 Date: Mon, 29 Nov 2010 17:19:30 -0800 From: Andres Salomon To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-geode@lists.infradead.org, dsd@laptop.org, cjb@laptop.org, stable@kernel.org Subject: [PATCH] cs5535-gpio: apply CS5536 errata workaround for GPIOs Message-ID: <20101129171930.2297083d@queued.net> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2411 Lines: 68 The AMD Geode CS5536 Companion Device Silicon Revision B1 Specification Update mentions the follow as issue #36: "Atomic write transactions to the atomic GPIO High Bank Feature Bit registers should only affect the bits selected [...]" "after Suspend, an atomic write transaction [...] will clear all non-selected bits of the accessed register." In other words, writing to the high bank for a single GPIO bit will clear every other GPIO bit (but only sometimes after a suspend). The workaround described is obvious and simple; do a read-modify-write. This patch does that, and documents why we're doing it. Signed-off-by: Andres Salomon --- drivers/gpio/cs5535-gpio.c | 16 ++++++++++++++-- 1 files changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/gpio/cs5535-gpio.c b/drivers/gpio/cs5535-gpio.c index e23c068..599f6c9 100644 --- a/drivers/gpio/cs5535-gpio.c +++ b/drivers/gpio/cs5535-gpio.c @@ -56,6 +56,18 @@ static struct cs5535_gpio_chip { * registers, see include/linux/cs5535.h. */ +static void errata_outl(u32 val, unsigned long addr) +{ + /* + * According to the CS5536 errata (#36), after suspend + * a write to the high bank GPIO register will clear all + * non-selected bits; the recommended workaround is a + * read-modify-write operation. + */ + val |= inl(addr); + outl(val, addr); +} + static void __cs5535_gpio_set(struct cs5535_gpio_chip *chip, unsigned offset, unsigned int reg) { @@ -64,7 +76,7 @@ static void __cs5535_gpio_set(struct cs5535_gpio_chip *chip, unsigned offset, outl(1 << offset, chip->base + reg); else /* high bank register */ - outl(1 << (offset - 16), chip->base + 0x80 + reg); + errata_outl(1 << (offset - 16), chip->base + 0x80 + reg); } void cs5535_gpio_set(unsigned offset, unsigned int reg) @@ -86,7 +98,7 @@ static void __cs5535_gpio_clear(struct cs5535_gpio_chip *chip, unsigned offset, outl(1 << (offset + 16), chip->base + reg); else /* high bank register */ - outl(1 << offset, chip->base + 0x80 + reg); + errata_outl(1 << offset, chip->base + 0x80 + reg); } void cs5535_gpio_clear(unsigned offset, unsigned int reg) -- 1.5.6.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/