From adbcec8862cd7e3737e1488a98239f95dc45688f Mon Sep 17 00:00:00 2001 From: Dmitry Osipenko Date: Thu, 19 Mar 2020 22:36:47 +0300 Subject: [PATCH] memory: tegra20-emc: Poll EMC-CaR handshake instead of waiting for interrupt The memory clock-rate change could be running on a non-boot CPU, while the boot CPU handles the EMC interrupt. This introduces an unnecessary latency since boot CPU should handle the interrupt and then notify the sibling CPU about clock-rate change completion. In some rare cases boot CPU could be in uninterruptible state for a significant time (like in a case of KASAN + NFS root), it could get to the point that completion timeouts before boot CPU gets a chance to handle interrupt. The solution is to get rid of the completion and replace it with interrupt-status polling. Signed-off-by: Dmitry Osipenko Signed-off-by: Thierry Reding --- drivers/memory/tegra/tegra20-emc.c | 28 +++++++++++----------------- 1 file changed, 11 insertions(+), 17 deletions(-) diff --git a/drivers/memory/tegra/tegra20-emc.c b/drivers/memory/tegra/tegra20-emc.c index f74dd417c874..027f46287dbf 100644 --- a/drivers/memory/tegra/tegra20-emc.c +++ b/drivers/memory/tegra/tegra20-emc.c @@ -7,11 +7,11 @@ #include #include -#include #include #include #include #include +#include #include #include #include @@ -144,7 +144,6 @@ struct emc_timing { struct tegra_emc { struct device *dev; - struct completion clk_handshake_complete; struct notifier_block clk_nb; struct clk *clk; void __iomem *regs; @@ -162,17 +161,13 @@ struct tegra_emc { static irqreturn_t tegra_emc_isr(int irq, void *data) { struct tegra_emc *emc = data; - u32 intmask = EMC_REFRESH_OVERFLOW_INT | EMC_CLKCHANGE_COMPLETE_INT; + u32 intmask = EMC_REFRESH_OVERFLOW_INT; u32 status; status = readl_relaxed(emc->regs + EMC_INTSTATUS) & intmask; if (!status) return IRQ_NONE; - /* notify about EMC-CAR handshake completion */ - if (status & EMC_CLKCHANGE_COMPLETE_INT) - complete(&emc->clk_handshake_complete); - /* notify about HW problem */ if (status & EMC_REFRESH_OVERFLOW_INT) dev_err_ratelimited(emc->dev, @@ -224,14 +219,13 @@ static int emc_prepare_timing_change(struct tegra_emc *emc, unsigned long rate) /* wait until programming has settled */ readl_relaxed(emc->regs + emc_timing_registers[i - 1]); - reinit_completion(&emc->clk_handshake_complete); - return 0; } static int emc_complete_timing_change(struct tegra_emc *emc, bool flush) { - unsigned long timeout; + int err; + u32 v; dev_dbg(emc->dev, "%s: flush %d\n", __func__, flush); @@ -242,11 +236,12 @@ static int emc_complete_timing_change(struct tegra_emc *emc, bool flush) return 0; } - 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"); - return -EIO; + err = readl_relaxed_poll_timeout_atomic(emc->regs + EMC_INTSTATUS, v, + v & EMC_CLKCHANGE_COMPLETE_INT, + 1, 100); + if (err) { + dev_err(emc->dev, "emc-car handshake timeout: %d\n", err); + return err; } return 0; @@ -412,7 +407,7 @@ tegra_emc_find_node_by_ram_code(struct device *dev) static int emc_setup_hw(struct tegra_emc *emc) { - u32 intmask = EMC_REFRESH_OVERFLOW_INT | EMC_CLKCHANGE_COMPLETE_INT; + u32 intmask = EMC_REFRESH_OVERFLOW_INT; u32 emc_cfg, emc_dbg; emc_cfg = readl_relaxed(emc->regs + EMC_CFG_2); @@ -686,7 +681,6 @@ static int tegra_emc_probe(struct platform_device *pdev) return -ENOMEM; } - init_completion(&emc->clk_handshake_complete); emc->clk_nb.notifier_call = tegra_emc_clk_change_notify; emc->dev = &pdev->dev;