Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758000AbaGORO2 (ORCPT ); Tue, 15 Jul 2014 13:14:28 -0400 Received: from mail-we0-f174.google.com ([74.125.82.174]:32897 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755734AbaGORCO (ORCPT ); Tue, 15 Jul 2014 13:02:14 -0400 From: Sam Asadi To: gregkh@linuxfoundation.org Cc: devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, Shawn Guo , Olof Johansson , sam-the-6 Subject: [PATCH 52/94] ARM: imx: fix shared gate clock Date: Tue, 15 Jul 2014 20:01:07 +0300 Message-Id: <1405443709-15288-52-git-send-email-asadi.samuel@gmail.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1405443709-15288-1-git-send-email-asadi.samuel@gmail.com> References: <1405443709-15288-1-git-send-email-asadi.samuel@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Shawn Guo Let's say clock A and B are two gate clocks that share the same register bit in hardware. Therefore they are registered as shared gate clocks with imx_clk_gate2_shared(). In a scenario that only clock A is enabled by clk_enable(A) while B is not used, the shared gate will be unexpectedly disabled in hardware. It happens because clk_enable(A) increments the share_count from 0 to 1, while clock B is unused to clock core, and therefore the core function will just disable B by calling clk->ops->disable() directly. The consequence of that call is share_count is decremented to 0 and the gate is disabled in hardware, even though clock A is still in use. The patch fixes the issue by initializing the share_count per hardware state and returns enable state per share_count from .is_enabled() hook, in case it's a shared gate. While at it, add a check in clk_gate2_disable() to ensure it's never called with a zero share_count. Reported-by: Fabio Estevam Fixes: f9f28cdf2167 ("ARM: imx: add shared gate clock support") Signed-off-by: Shawn Guo Tested-by: Fabio Estevam Signed-off-by: Olof Johansson Signed-off-by: sam-the-6 --- arch/arm/mach-imx/clk-gate2.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) diff --git a/arch/arm/mach-imx/clk-gate2.c b/arch/arm/mach-imx/clk-gate2.c index 4ba587d..84acdfd 100644 --- a/arch/arm/mach-imx/clk-gate2.c +++ b/arch/arm/mach-imx/clk-gate2.c @@ -67,8 +67,12 @@ static void clk_gate2_disable(struct clk_hw *hw) spin_lock_irqsave(gate->lock, flags); - if (gate->share_count && --(*gate->share_count) > 0) - goto out; + if (gate->share_count) { + if (WARN_ON(*gate->share_count == 0)) + goto out; + else if (--(*gate->share_count) > 0) + goto out; + } reg = readl(gate->reg); reg &= ~(3 << gate->bit_idx); @@ -78,19 +82,26 @@ out: spin_unlock_irqrestore(gate->lock, flags); } -static int clk_gate2_is_enabled(struct clk_hw *hw) +static int clk_gate2_reg_is_enabled(void __iomem *reg, u8 bit_idx) { - u32 reg; - struct clk_gate2 *gate = to_clk_gate2(hw); + u32 val = readl(reg); - reg = readl(gate->reg); - - if (((reg >> gate->bit_idx) & 1) == 1) + if (((val >> bit_idx) & 1) == 1) return 1; return 0; } +static int clk_gate2_is_enabled(struct clk_hw *hw) +{ + struct clk_gate2 *gate = to_clk_gate2(hw); + + if (gate->share_count) + return !!(*gate->share_count); + else + return clk_gate2_reg_is_enabled(gate->reg, gate->bit_idx); +} + static struct clk_ops clk_gate2_ops = { .enable = clk_gate2_enable, .disable = clk_gate2_disable, @@ -116,6 +127,10 @@ struct clk *clk_register_gate2(struct device *dev, const char *name, gate->bit_idx = bit_idx; gate->flags = clk_gate2_flags; gate->lock = lock; + + /* Initialize share_count per hardware state */ + if (share_count) + *share_count = clk_gate2_reg_is_enabled(reg, bit_idx) ? 1 : 0; gate->share_count = share_count; init.name = name; -- 1.7.10.4 -- 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/