[PATCH v5 3/3] ARM: imx6plus: optionally enable internal routing of clk_enet_ref

[Sven Van Asbroeck <thesven73@gmail.com>]

On imx6, the ethernet reference clock (clk_enet_ref) can be generated
by either the imx6, or an external source (e.g. an oscillator or the
PHY). When generated by the imx6, the clock source (from ANATOP)
must be routed to the input of clk_enet_ref via two pads on the SoC,
typically via a dedicated track on the PCB.

On an imx6 plus however, there is a new setting which enables this
clock to be routed internally on the SoC, from its ANATOP clock
source, straight to clk_enet_ref, without having to go through
the SoC pads.

Enable internal routing if the fsl,ptpclk-bypass-pad boolean
property is present in the "fsl,imx6q-fec" devicetree node.

Link: https://lore.kernel.org/lkml/CAOMZO5BYC3DmE_G0XRwRH9vSJiVVvKbtznODyntsAuorF=HoqA@mail.gmail.com/
Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
---

Tree: v5.8-rc3

v4 -> v5:
  - identified that existing imx6q-plus boards could break ethernet if v4
    patch is applied.
    reached consensus: prevent breakage by requiring an explicit devicetree
    property for internal ptp clk routing.
    Link: https://lore.kernel.org/lkml/CAOMZO5BYC3DmE_G0XRwRH9vSJiVVvKbtznODyntsAuorF=HoqA@mail.gmail.com/
v3 -> v4:
  - avoid double-check for IS_ERR(gpr) by including Fabio Estevam's
    patch.
v2 -> v3:
  - remove check for imx6q, which is already implied when
    of_machine_is_compatible("fsl,imx6qp")
v1 -> v2:
  - Fabio Estevam: use of_machine_is_compatible() to determine if we
    are running on an imx6 plus.

To: Shawn Guo <shawnguo@kernel.org>
To: Andy Duan <fugang.duan@nxp.com>
To: Rob Herring <robh+dt@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org

 arch/arm/mach-imx/mach-imx6q.c              | 14 ++++++++++++++
 include/linux/mfd/syscon/imx6q-iomuxc-gpr.h |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/arch/arm/mach-imx/mach-imx6q.c b/arch/arm/mach-imx/mach-imx6q.c
index ae89ad93ca83..ac62994eb7ba 100644
--- a/arch/arm/mach-imx/mach-imx6q.c
+++ b/arch/arm/mach-imx/mach-imx6q.c
@@ -204,6 +204,20 @@ static void __init imx6q_1588_init(void)
 	regmap_update_bits(gpr, IOMUXC_GPR1, IMX6Q_GPR1_ENET_CLK_SEL_MASK,
 			   clksel);
 
+	/*
+	 * On imx6 plus, enet_ref from ANATOP/CCM can be internally routed to
+	 * be the PTP clock source, instead of having to be routed through
+	 * pads.
+	 */
+	if (of_machine_is_compatible("fsl,imx6qp")) {
+		clksel = of_property_read_bool(np, "fsl,ptpclk-bypass-pad") ?
+				IMX6Q_GPR5_ENET_TXCLK_SEL_PLL :
+				IMX6Q_GPR5_ENET_TXCLK_SEL_PAD;
+		regmap_update_bits(gpr, IOMUXC_GPR5,
+				   IMX6Q_GPR5_ENET_TXCLK_SEL_MASK, clksel);
+	}
+
+
 	clk_put(enet_ref);
 put_ptp_clk:
 	clk_put(ptp_clk);
diff --git a/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h b/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
index d4b5e527a7a3..58377002427f 100644
--- a/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
+++ b/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
@@ -240,6 +240,9 @@
 #define IMX6Q_GPR4_IPU_RD_CACHE_CTL		BIT(0)
 
 #define IMX6Q_GPR5_L2_CLK_STOP			BIT(8)
+#define IMX6Q_GPR5_ENET_TXCLK_SEL_MASK		BIT(9)
+#define IMX6Q_GPR5_ENET_TXCLK_SEL_PAD		0
+#define IMX6Q_GPR5_ENET_TXCLK_SEL_PLL		BIT(9)
 #define IMX6Q_GPR5_SATA_SW_PD			BIT(10)
 #define IMX6Q_GPR5_SATA_SW_RST			BIT(11)
 
-- 
2.17.1