linux-kernel - [PATCH] Marvell MDIO clock related changes.

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Date:   Fri, 15 Apr 2022 07:30:26 -0700
From:   Piyush Malgujar <pmalgujar@...vell.com>
To:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <cchavva@...vell.com>, Piyush Malgujar <pmalgujar@...vell.com>,
        "Damian Eppel" <deppel@...vell.com>, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH] Marvell MDIO clock related changes.

This patch includes following support related to MDIO Clock:

1) clock gating:
The purpose of this change is to apply clock gating for MDIO clock when there is no transaction happening.
This will stop the MDC clock toggling in idle scenario.

2) Marvell MDIO clock frequency attribute change:
This MDIO change provides an option for user to have the bus speed set to their needs which is otherwise set
to default(3.125 MHz). In case someone needs to use this attribute, they have to add an extra attribute clock-freq
in the mdio entry in their DTS and this driver will support the rest.

The changes are made in a way that the clock will set to the nearest possible value based on the clock calculation
and required frequency from DTS. Below are some possible values:
default:3.125 MHz
Max:16.67 MHz

These changes has been verified internally with Marvell SoCs 9x and 10x series.

Signed-off-by: Piyush Malgujar <pmalgujar@...vell.com>
Signed-off-by: Damian Eppel <deppel@...vell.com>
---
 drivers/net/mdio/mdio-cavium.h  |  1 +
 drivers/net/mdio/mdio-thunder.c | 65 +++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/drivers/net/mdio/mdio-cavium.h b/drivers/net/mdio/mdio-cavium.h
index a2245d436f5dae4d6424b7c7bfca0aa969a3b3ad..ed4c48d8a38bd80e6a169f7a6d90c1f2a0daccfc 100644
--- a/drivers/net/mdio/mdio-cavium.h
+++ b/drivers/net/mdio/mdio-cavium.h
@@ -92,6 +92,7 @@ struct cavium_mdiobus {
 	struct mii_bus *mii_bus;
 	void __iomem *register_base;
 	enum cavium_mdiobus_mode mode;
+	u32 clk_freq;
 };
 
 #ifdef CONFIG_CAVIUM_OCTEON_SOC
diff --git a/drivers/net/mdio/mdio-thunder.c b/drivers/net/mdio/mdio-thunder.c
index 822d2cdd2f3599025f3e79d4243337c18114c951..642d08aff3f7f849102992a891790e900b111d5c 100644
--- a/drivers/net/mdio/mdio-thunder.c
+++ b/drivers/net/mdio/mdio-thunder.c
@@ -19,6 +19,46 @@ struct thunder_mdiobus_nexus {
 	struct cavium_mdiobus *buses[4];
 };
 
+#define _calc_clk_freq(_phase) (100000000U / (2 * (_phase)))
+#define _calc_sample(_phase) (2 * (_phase) - 3)
+
+#define PHASE_MIN 3
+#define PHASE_DFLT 16
+#define DFLT_CLK_FREQ _calc_clk_freq(PHASE_DFLT)
+#define MAX_CLK_FREQ _calc_clk_freq(PHASE_MIN)
+
+static inline u32 _config_clk(u32 req_freq, u32 *phase, u32 *sample)
+{
+	unsigned int p;
+	u32 freq = 0, freq_prev;
+
+	for (p = PHASE_MIN; p < PHASE_DFLT; p++) {
+		freq_prev = freq;
+		freq = _calc_clk_freq(p);
+
+		if (req_freq >= freq)
+			break;
+	}
+
+	if (p == PHASE_DFLT)
+		freq = DFLT_CLK_FREQ;
+
+	if (p == PHASE_MIN || p == PHASE_DFLT)
+		goto out;
+
+	/* Check which clock value from the identified range
+	 * is closer to the requested value
+	 */
+	if ((freq_prev - req_freq) < (req_freq - freq)) {
+		p = p - 1;
+		freq = freq_prev;
+	}
+out:
+	*phase = p;
+	*sample = _calc_sample(p);
+	return freq;
+}
+
 static int thunder_mdiobus_pci_probe(struct pci_dev *pdev,
 				     const struct pci_device_id *ent)
 {
@@ -59,6 +99,8 @@ static int thunder_mdiobus_pci_probe(struct pci_dev *pdev,
 		struct mii_bus *mii_bus;
 		struct cavium_mdiobus *bus;
 		union cvmx_smix_en smi_en;
+		union cvmx_smix_clk smi_clk;
+		u32 req_clk_freq;
 
 		/* If it is not an OF node we cannot handle it yet, so
 		 * exit the loop.
@@ -87,6 +129,29 @@ static int thunder_mdiobus_pci_probe(struct pci_dev *pdev,
 		bus->register_base = nexus->bar0 +
 			r.start - pci_resource_start(pdev, 0);
 
+		smi_clk.u64 = oct_mdio_readq(bus->register_base + SMI_CLK);
+		smi_clk.s.clk_idle = 1;
+
+		if (!of_property_read_u32(node, "clock-freq", &req_clk_freq)) {
+			u32 phase, sample;
+
+			dev_info(&pdev->dev, "requested bus clock frequency=%d\n",
+				 req_clk_freq);
+
+			 bus->clk_freq = _config_clk(req_clk_freq,
+						     &phase, &sample);
+
+			 smi_clk.s.phase = phase;
+			 smi_clk.s.sample_hi = (sample >> 4) & 0x1f;
+			 smi_clk.s.sample = sample & 0xf;
+		} else {
+			bus->clk_freq = DFLT_CLK_FREQ;
+		}
+
+		oct_mdio_writeq(smi_clk.u64, bus->register_base + SMI_CLK);
+		dev_info(&pdev->dev, "bus clock frequency set to %d\n",
+			 bus->clk_freq);
+
 		smi_en.u64 = 0;
 		smi_en.s.en = 1;
 		oct_mdio_writeq(smi_en.u64, bus->register_base + SMI_EN);
-- 
2.17.1