drivers/clk/sunxi/clk-a20-gmac.c

Source file repositories/reference/linux-study-clean/drivers/clk/sunxi/clk-a20-gmac.c

File Facts

System
Linux kernel
Corpus path
drivers/clk/sunxi/clk-a20-gmac.c
Extension
.c
Size
3209 bytes
Lines
114
Domain
Driver Families
Bucket
drivers/clk
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 2013 Emilio López
 * Emilio López <emilio@elopez.com.ar>
 *
 * Copyright 2013 Chen-Yu Tsai
 * Chen-Yu Tsai <wens@csie.org>
 */

#include <linux/clk-provider.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/slab.h>

static DEFINE_SPINLOCK(gmac_lock);


#define SUN7I_A20_GMAC_GPIT	2
#define SUN7I_A20_GMAC_MASK	0x3
#define SUN7I_A20_GMAC_PARENTS	2

static u32 sun7i_a20_gmac_mux_table[SUN7I_A20_GMAC_PARENTS] = {
	0x00, /* Select mii_phy_tx_clk */
	0x02, /* Select gmac_int_tx_clk */
};

/**
 * sun7i_a20_gmac_clk_setup - Setup function for A20/A31 GMAC clock module
 * @node: &struct device_node for the clock
 *
 * This clock looks something like this
 *                               ________________________
 *  MII TX clock from PHY >-----|___________    _________|----> to GMAC core
 *  GMAC Int. RGMII TX clk >----|___________\__/__gate---|----> to PHY
 *  Ext. 125MHz RGMII TX clk >--|__divider__/            |
 *                              |________________________|
 *
 * The external 125 MHz reference is optional, i.e. GMAC can use its
 * internal TX clock just fine. The A31 GMAC clock module does not have
 * the divider controls for the external reference.
 *
 * To keep it simple, let the GMAC use either the MII TX clock for MII mode,
 * and its internal TX clock for GMII and RGMII modes. The GMAC driver should
 * select the appropriate source and gate/ungate the output to the PHY.
 *
 * Only the GMAC should use this clock. Altering the clock so that it doesn't
 * match the GMAC's operation parameters will result in the GMAC not being
 * able to send traffic out. The GMAC driver should set the clock rate and
 * enable/disable this clock to configure the required state. The clock
 * driver then responds by auto-reparenting the clock.
 */
static void __init sun7i_a20_gmac_clk_setup(struct device_node *node)
{
	struct clk *clk;
	struct clk_mux *mux;
	struct clk_gate *gate;
	const char *clk_name = node->name;
	const char *parents[SUN7I_A20_GMAC_PARENTS];
	void __iomem *reg;

	if (of_property_read_string(node, "clock-output-names", &clk_name))
		return;

	/* allocate mux and gate clock structs */
	mux = kzalloc_obj(struct clk_mux);
	if (!mux)
		return;

	gate = kzalloc_obj(struct clk_gate);
	if (!gate)
		goto free_mux;

	/* gmac clock requires exactly 2 parents */
	if (of_clk_parent_fill(node, parents, 2) != 2)
		goto free_gate;

	reg = of_iomap(node, 0);
	if (!reg)
		goto free_gate;

	/* set up gate and fixed rate properties */
	gate->reg = reg;
	gate->bit_idx = SUN7I_A20_GMAC_GPIT;
	gate->lock = &gmac_lock;
	mux->reg = reg;
	mux->mask = SUN7I_A20_GMAC_MASK;
	mux->table = sun7i_a20_gmac_mux_table;
	mux->lock = &gmac_lock;

Annotation

Implementation Notes