linux-kernel - [PATCH 2/2] PCI: uniphier: Add checking whether PERST# is deasserted

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Date:   Thu,  7 Nov 2019 13:58:15 +0900
From:   Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <andrew.murray@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Masami Hiramatsu <masami.hiramatsu@...aro.org>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
Subject: [PATCH 2/2] PCI: uniphier: Add checking whether PERST# is deasserted

When PERST# is asserted once, EP configuration will be initialized.
If PERST# has been already deasserted, it isn't necessary to assert
here.

This checks whether PERST# is deasserted using PCL_PINMON register,
and adds omit controlling PERST#.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
---
 drivers/pci/controller/dwc/pcie-uniphier.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-uniphier.c b/drivers/pci/controller/dwc/pcie-uniphier.c
index 8fd7bad..1ea4220 100644
--- a/drivers/pci/controller/dwc/pcie-uniphier.c
+++ b/drivers/pci/controller/dwc/pcie-uniphier.c
@@ -22,6 +22,9 @@
 
 #include "pcie-designware.h"
 
+#define PCL_PINMON			0x0028
+#define PCL_PINMON_PERST_OUT		BIT(16)
+
 #define PCL_PINCTRL0			0x002c
 #define PCL_PERST_PLDN_REGEN		BIT(12)
 #define PCL_PERST_NOE_REGEN		BIT(11)
@@ -100,6 +103,11 @@ static void uniphier_pcie_init_rc(struct uniphier_pcie_priv *priv)
 	val |= PCL_SYS_AUX_PWR_DET;
 	writel(val, priv->base + PCL_APP_PM0);
 
+	/* return if PERST# is already deasserted */
+	val = readl(priv->base + PCL_PINMON);
+	if (val & PCL_PINMON_PERST_OUT)
+		return;
+
 	/* assert PERST# */
 	val = readl(priv->base + PCL_PINCTRL0);
 	val &= ~(PCL_PERST_NOE_REGVAL | PCL_PERST_OUT_REGVAL
-- 
2.7.4