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[79.139.233.37]) by smtp.gmail.com with ESMTPSA id m13sm3279818lfo.40.2019.12.19.18.09.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Dec 2019 18:09:22 -0800 (PST) From: Dmitry Osipenko To: Thierry Reding , Jonathan Hunter Cc: linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/3] memory: tegra30-emc: Firm up suspend/resume sequence Date: Fri, 20 Dec 2019 05:08:47 +0300 Message-Id: <20191220020849.11175-2-digetx@gmail.com> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191220020849.11175-1-digetx@gmail.com> References: <20191220020849.11175-1-digetx@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The current code doesn't prevent race conditions of suspend/resume vs CCF. Let's take exclusive control over the EMC clock during suspend in a way that is free from race conditions. Signed-off-by: Dmitry Osipenko --- drivers/memory/tegra/tegra30-emc.c | 38 ++++++++++++++++-------------- 1 file changed, 20 insertions(+), 18 deletions(-) diff --git a/drivers/memory/tegra/tegra30-emc.c b/drivers/memory/tegra/tegra30-emc.c index 0b6a5e451ea3..770808da957d 100644 --- a/drivers/memory/tegra/tegra30-emc.c +++ b/drivers/memory/tegra/tegra30-emc.c @@ -345,7 +345,6 @@ struct tegra_emc { bool vref_cal_toggle : 1; bool zcal_long : 1; bool dll_on : 1; - bool prepared : 1; bool bad_state : 1; }; @@ -751,9 +750,6 @@ static int emc_prepare_timing_change(struct tegra_emc *emc, unsigned long rate) /* interrupt can be re-enabled now */ enable_irq(emc->irq); - emc->bad_state = false; - emc->prepared = true; - return 0; } @@ -762,13 +758,12 @@ static int emc_complete_timing_change(struct tegra_emc *emc, { struct emc_timing *timing = emc_find_timing(emc, rate); unsigned long timeout; - int ret; + int err; timeout = wait_for_completion_timeout(&emc->clk_handshake_complete, msecs_to_jiffies(100)); if (timeout == 0) { dev_err(emc->dev, "emc-car handshake failed\n"); - emc->bad_state = true; return -EIO; } @@ -790,22 +785,23 @@ static int emc_complete_timing_change(struct tegra_emc *emc, udelay(2); /* update restored timing */ - ret = emc_seq_update_timing(emc); - if (ret) - emc->bad_state = true; + err = emc_seq_update_timing(emc); /* restore early ACK */ mc_writel(emc->mc, emc->mc_override, MC_EMEM_ARB_OVERRIDE); - emc->prepared = false; + if (err) + return err; + + emc->bad_state = false; - return ret; + return 0; } static int emc_unprepare_timing_change(struct tegra_emc *emc, unsigned long rate) { - if (emc->prepared && !emc->bad_state) { + if (!emc->bad_state) { /* shouldn't ever happen in practice */ dev_err(emc->dev, "timing configuration can't be reverted\n"); emc->bad_state = true; @@ -1181,13 +1177,17 @@ static int tegra_emc_probe(struct platform_device *pdev) static int tegra_emc_suspend(struct device *dev) { struct tegra_emc *emc = dev_get_drvdata(dev); + int err; + + /* take exclusive control over the clock's rate */ + err = clk_rate_exclusive_get(emc->clk); + if (err) { + dev_err(emc->dev, "failed to acquire clk: %d\n", err); + return err; + } - /* - * Suspending in a bad state will hang machine. The "prepared" var - * shall be always false here unless it's a kernel bug that caused - * suspending in a wrong order. - */ - if (WARN_ON(emc->prepared) || emc->bad_state) + /* suspending in a bad state will hang machine */ + if (WARN(emc->bad_state, "hardware in a bad state\n")) return -EINVAL; emc->bad_state = true; @@ -1202,6 +1202,8 @@ static int tegra_emc_resume(struct device *dev) emc_setup_hw(emc); emc->bad_state = false; + clk_rate_exclusive_put(emc->clk); + return 0; } -- 2.24.0