Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753281Ab2FMKXF (ORCPT ); Wed, 13 Jun 2012 06:23:05 -0400 Received: from hqemgate04.nvidia.com ([216.228.121.35]:6067 "EHLO hqemgate04.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753019Ab2FMKW2 (ORCPT ); Wed, 13 Jun 2012 06:22:28 -0400 X-PGP-Universal: processed; by hqnvupgp08.nvidia.com on Wed, 13 Jun 2012 03:21:51 -0700 From: Laxman Dewangan To: , , , , CC: , , , Laxman Dewangan Subject: [PATCH V3 1/4] i2c: tegra: make sure register writes completes Date: Wed, 13 Jun 2012 15:42:36 +0530 Message-ID: <1339582359-7911-2-git-send-email-ldewangan@nvidia.com> X-Mailer: git-send-email 1.7.1.1 In-Reply-To: <1339582359-7911-1-git-send-email-ldewangan@nvidia.com> References: <1339582359-7911-1-git-send-email-ldewangan@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1601 Lines: 43 The Tegra PPSB (an peripheral bus) queues writes transactions. In order to guarantee that writes have completed before a certain time, a read transaction to a register on the same bus must be executed. This is necessary in situations such as when clearing an interrupt status or enable, so that when returning from an interrupt handler, the HW has already de-asserted its interrupt status output, which will avoid spurious interrupts. Signed-off-by: Laxman Dewangan --- Changes from V1: - Using the readback for mask/unmask of irq also. Changes from V2: - Read back is done whenever write happen in i2c register other than TX FIFO. drivers/i2c/busses/i2c-tegra.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c index 8b2e555..785f7f7 100644 --- a/drivers/i2c/busses/i2c-tegra.c +++ b/drivers/i2c/busses/i2c-tegra.c @@ -165,6 +165,10 @@ static void i2c_writel(struct tegra_i2c_dev *i2c_dev, u32 val, unsigned long reg) { writel(val, i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg)); + + /* Read back register to make sure that register writes completed */ + if (reg != I2C_TX_FIFO) + readl(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg)); } static u32 i2c_readl(struct tegra_i2c_dev *i2c_dev, unsigned long reg) -- 1.7.1.1 -- 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/