From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 59CA8229678; Thu, 12 Dec 2024 16:54:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734022486; cv=none; b=bcB6LmA68rbligC1kbfzZlCM66Mbr5Sy3BYeJr6EmCgff/QJLGzYZAW+486VC48Xjy7pOM8t2FwjdF4fcO92T549rMD0naZzAMq3jDXCCwKCw4uZDZk6usf/LAMNS4Jzn5f96SfDVKHNBSUPUGfZhZt/GXcKqn2O277xxmJy1Ng= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734022486; c=relaxed/simple; bh=HYL4k71H/uB4nCfWpaHF52uWKXzai8MWho4+4ptZvbk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Myti2ttFLTqCKrzztY0lcVhIkF6E9t85VKJNWyt0D7IftvZGj+dmBlPSYxzs/NUfoRHZeP2mJlSG6RZr3I9aorawUkx8JA97AZ3exoonVX1Glyt+KB56AusedqPnxFVcIu9qD4x4ab31UWnazV/VhhRqU2QmbHYL1ZtcUBtrqeE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Yfl2exch; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Yfl2exch" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3AB2C4CED0; Thu, 12 Dec 2024 16:54:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1734022486; bh=HYL4k71H/uB4nCfWpaHF52uWKXzai8MWho4+4ptZvbk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Yfl2exchBjLq4BGFRsQX4VF0udAkLy7ZStYuj5ut3DVaQWqmdM3FUFO46w7SX8hos j4IKV+MpM93ksTTgQE78HbCdcPsROGdilTA9UOUurfQRfoKt6KJ+Z+MSNtRfL6AjXc ASJ5xMXFgZ0oY6skrvL2PgqUv2C2NyvMiaXgOMzw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Peng Fan , Abel Vesa , Sasha Levin Subject: [PATCH 5.15 223/565] clk: imx: lpcg-scu: SW workaround for errata (e10858) Date: Thu, 12 Dec 2024 15:56:58 +0100 Message-ID: <20241212144320.304677003@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241212144311.432886635@linuxfoundation.org> References: <20241212144311.432886635@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peng Fan [ Upstream commit 5ee063fac85656bea9cfe3570af147ba1701ba18 ] Back-to-back LPCG writes can be ignored by the LPCG register due to a HW bug. The writes need to be separated by at least 4 cycles of the gated clock. See https://www.nxp.com.cn/docs/en/errata/IMX8_1N94W.pdf The workaround is implemented as follows: 1. For clocks running greater than or equal to 24MHz, a read followed by the write will provide sufficient delay. 2. For clocks running below 24MHz, add a delay of 4 clock cylces after the write to the LPCG register. Fixes: 2f77296d3df9 ("clk: imx: add lpcg clock support") Signed-off-by: Peng Fan Reviewed-by: Abel Vesa Link: https://lore.kernel.org/r/20241027-imx-clk-v1-v3-1-89152574d1d7@nxp.com Signed-off-by: Abel Vesa Signed-off-by: Sasha Levin --- drivers/clk/imx/clk-lpcg-scu.c | 37 ++++++++++++++++++++++++++-------- 1 file changed, 29 insertions(+), 8 deletions(-) diff --git a/drivers/clk/imx/clk-lpcg-scu.c b/drivers/clk/imx/clk-lpcg-scu.c index dd5abd09f3e20..620afdf8dc03e 100644 --- a/drivers/clk/imx/clk-lpcg-scu.c +++ b/drivers/clk/imx/clk-lpcg-scu.c @@ -6,10 +6,12 @@ #include #include +#include #include #include #include #include +#include #include "clk-scu.h" @@ -41,6 +43,29 @@ struct clk_lpcg_scu { #define to_clk_lpcg_scu(_hw) container_of(_hw, struct clk_lpcg_scu, hw) +/* e10858 -LPCG clock gating register synchronization errata */ +static void lpcg_e10858_writel(unsigned long rate, void __iomem *reg, u32 val) +{ + writel(val, reg); + + if (rate >= 24 * HZ_PER_MHZ || rate == 0) { + /* + * The time taken to access the LPCG registers from the AP core + * through the interconnect is longer than the minimum delay + * of 4 clock cycles required by the errata. + * Adding a readl will provide sufficient delay to prevent + * back-to-back writes. + */ + readl(reg); + } else { + /* + * For clocks running below 24MHz, wait a minimum of + * 4 clock cycles. + */ + ndelay(4 * (DIV_ROUND_UP(1000 * HZ_PER_MHZ, rate))); + } +} + static int clk_lpcg_scu_enable(struct clk_hw *hw) { struct clk_lpcg_scu *clk = to_clk_lpcg_scu(hw); @@ -57,7 +82,8 @@ static int clk_lpcg_scu_enable(struct clk_hw *hw) val |= CLK_GATE_SCU_LPCG_HW_SEL; reg |= val << clk->bit_idx; - writel(reg, clk->reg); + + lpcg_e10858_writel(clk_hw_get_rate(hw), clk->reg, reg); spin_unlock_irqrestore(&imx_lpcg_scu_lock, flags); @@ -74,7 +100,7 @@ static void clk_lpcg_scu_disable(struct clk_hw *hw) reg = readl_relaxed(clk->reg); reg &= ~(CLK_GATE_SCU_LPCG_MASK << clk->bit_idx); - writel(reg, clk->reg); + lpcg_e10858_writel(clk_hw_get_rate(hw), clk->reg, reg); spin_unlock_irqrestore(&imx_lpcg_scu_lock, flags); } @@ -145,13 +171,8 @@ static int __maybe_unused imx_clk_lpcg_scu_resume(struct device *dev) { struct clk_lpcg_scu *clk = dev_get_drvdata(dev); - /* - * FIXME: Sometimes writes don't work unless the CPU issues - * them twice - */ - - writel(clk->state, clk->reg); writel(clk->state, clk->reg); + lpcg_e10858_writel(0, clk->reg, clk->state); dev_dbg(dev, "restore lpcg state 0x%x\n", clk->state); return 0; -- 2.43.0