Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752467AbdHPJrx (ORCPT ); Wed, 16 Aug 2017 05:47:53 -0400 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:43905 "EHLO metis.ext.4.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752262AbdHPJr1 (ORCPT ); Wed, 16 Aug 2017 05:47:27 -0400 From: Philipp Zabel To: linux-kernel@vger.kernel.org Cc: Alexandru Gagniuc , Andre Przywara , Maxime Coquelin , Alexandre Torgue , Maxime Ripard , Chen-Yu Tsai , Baoyou Xie , Eugeniy Paltsev , Steffen Trumtrar , Dinh Nguyen , =?UTF-8?q?Andreas=20F=C3=A4rber?= , linux-arm-kernel@lists.infradead.org, kernel@pengutronix.de, Philipp Zabel Subject: [PATCH v3 5/5] reset: simple: read back to make sure changes are applied Date: Wed, 16 Aug 2017 11:47:01 +0200 Message-Id: <20170816094701.30678-6-p.zabel@pengutronix.de> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170816094701.30678-1-p.zabel@pengutronix.de> References: <20170816094701.30678-1-p.zabel@pengutronix.de> X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::7 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1404 Lines: 40 Read back the register after setting or clearing a reset bit to make sure that the changes are applied to the reset controller hardware. Theoretically, this avoids the write to stay stuck in a store buffer during the delay of an assert-delay-deassert sequence, and makes sure that the reset really is asserted for the specified duration. Signed-off-by: Philipp Zabel --- drivers/reset/reset-simple.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/reset/reset-simple.c b/drivers/reset/reset-simple.c index 13e7d5559acc9..d98a7e7d802d1 100644 --- a/drivers/reset/reset-simple.c +++ b/drivers/reset/reset-simple.c @@ -39,17 +39,20 @@ static int reset_simple_set(struct reset_controller_dev *rcdev, int reg_width = sizeof(u32); int bank = id / (reg_width * BITS_PER_BYTE); int offset = id % (reg_width * BITS_PER_BYTE); + void __iomem *addr = data->membase + (bank * reg_width); unsigned long flags; u32 reg; spin_lock_irqsave(&data->lock, flags); - reg = readl(data->membase + (bank * reg_width)); + reg = readl(addr); if (assert ^ data->active_low) reg |= BIT(offset); else reg &= ~BIT(offset); - writel(reg, data->membase + (bank * reg_width)); + writel(reg, addr); + /* Read back to make sure the write doesn't linger in a store buffer */ + readl(addr); spin_unlock_irqrestore(&data->lock, flags); -- 2.11.0