linux-kernel - [PATCH v2 5/6] PCI: tegra: Make sure the PCIe PLL is really reset

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Message-Id: <1409065064-17617-6-git-send-email-thierry.reding@gmail.com>
Date:	Tue, 26 Aug 2014 16:57:43 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Stephen Warren <swarren@...dotorg.org>, linux-pci@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 5/6] PCI: tegra: Make sure the PCIe PLL is really reset

From: Eric Yuen <eyuen@...dia.com>

Depending on the prior state of the controller, the PLL reset may not be
pulsed. Clear the register bit and set it after a small delay to ensure
that the PLL is really reset.

Signed-off-by: Eric Yuen <eyuen@...dia.com>
Signed-off-by: Thierry Reding <treding@...dia.com>
---
 drivers/pci/host/pci-tegra.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
index 8264bce77750..0ce43764dd36 100644
--- a/drivers/pci/host/pci-tegra.c
+++ b/drivers/pci/host/pci-tegra.c
@@ -849,6 +849,13 @@ static int tegra_pcie_enable_controller(struct tegra_pcie *pcie)
 	value |= PADS_PLL_CTL_REFCLK_INTERNAL_CML | soc->tx_ref_sel;
 	pads_writel(pcie, value, soc->pads_pll_ctl);
 
+	/* reset PLL */
+	value = pads_readl(pcie, soc->pads_pll_ctl);
+	value &= ~PADS_PLL_CTL_RST_B4SM;
+	pads_writel(pcie, value, soc->pads_pll_ctl);
+
+	usleep_range(20, 100);
+
 	/* take PLL out of reset  */
 	value = pads_readl(pcie, soc->pads_pll_ctl);
 	value |= PADS_PLL_CTL_RST_B4SM;
-- 
2.0.4

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