[PATCH v1] ARM: imx6plus: enable internal routing of clk_enet_ref where possible

[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.

Board designs where the clock is generated by the imx6 should not
be affected by routing the clock internally. Therefore on a plus,
we can enable internal routing by default.

To: Shawn Guo <shawnguo@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
Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
---
 arch/arm/mach-imx/mach-imx6q.c              | 18 ++++++++++++++++++
 include/linux/mfd/syscon/imx6q-iomuxc-gpr.h |  1 +
 2 files changed, 19 insertions(+)

Tree: next-20200613

diff --git a/arch/arm/mach-imx/mach-imx6q.c b/arch/arm/mach-imx/mach-imx6q.c
index 85c084a716ab..4d22567bb650 100644
--- a/arch/arm/mach-imx/mach-imx6q.c
+++ b/arch/arm/mach-imx/mach-imx6q.c
@@ -203,6 +203,24 @@ static void __init imx6q_1588_init(void)
 	else
 		pr_err("failed to find fsl,imx6q-iomuxc-gpr regmap\n");
 
+	/*
+	 * 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.
+	 * Board designs which route the ANATOP/CCM clock through pads are
+	 * unaffected when routing happens internally. So on these designs,
+	 * route internally by default.
+	 */
+	if (clksel == IMX6Q_GPR1_ENET_CLK_SEL_ANATOP && cpu_is_imx6q() &&
+			imx_get_soc_revision() >= IMX_CHIP_REVISION_2_0) {
+		if (!IS_ERR(gpr))
+			regmap_update_bits(gpr, IOMUXC_GPR5,
+					IMX6Q_GPR5_ENET_TXCLK_SEL,
+					IMX6Q_GPR5_ENET_TXCLK_SEL);
+		else
+			pr_err("failed to find fsl,imx6q-iomuxc-gpr regmap\n");
+		}
+
 	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..eb65d48da0df 100644
--- a/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
+++ b/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
@@ -240,6 +240,7 @@
 #define IMX6Q_GPR4_IPU_RD_CACHE_CTL		BIT(0)
 
 #define IMX6Q_GPR5_L2_CLK_STOP			BIT(8)
+#define IMX6Q_GPR5_ENET_TXCLK_SEL		BIT(9)
 #define IMX6Q_GPR5_SATA_SW_PD			BIT(10)
 #define IMX6Q_GPR5_SATA_SW_RST			BIT(11)
 
-- 
2.17.1