Commit 8f93662d authored by Serge Semin's avatar Serge Semin Committed by Arnd Bergmann
Browse files

bus: Add Baikal-T1 APB-bus driver 

Baikal-T1 AXI-APB bridge is used to access the SoC subsystem CSRs.
IO requests are routed to this bus by means of the DW AMBA 3 AXI
Interconnect. In case if an attempted APB transaction stays with no
response for a pre-defined time an interrupt occurs and the bus gets
freed for a next operation. This driver provides the interrupt handler
to detect the erroneous address, prints an error message about the
address fault, updates an errors counter. The counter and the APB-bus
operations timeout can be accessed via corresponding sysfs nodes.
A dedicated sysfs-node can be also used to artificially cause the
bus errors described above.

[arnd: fix build warnings for missing includes and wrong return types]

Link: https://lore.kernel.org/r/20200526125928.17096-6-Sergey.Semin@baikalelectronics.ru


Signed-off-by: default avatarSerge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Olof Johansson <olof@lixom.net>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: soc@kernel.org
Cc: devicetree@vger.kernel.org
Reported-by: default avatarkbuild test robot <lkp@intel.com>
Reported-by: default avatarkbuild test robot <lkp@intel.com>
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
parent 63cb7713

drivers/bus/Kconfig

+15 −0
Original line number Diff line number Diff line
@@ -29,6 +29,21 @@ config BRCMSTB_GISB_ARB 
	  arbiter. This driver provides timeout and target abort error handling

	  and internal bus master decoding.



config BT1_APB

	tristate "Baikal-T1 APB-bus driver"

	depends on MIPS_BAIKAL_T1 || COMPILE_TEST

	select REGMAP_MMIO

	help

	  Baikal-T1 AXI-APB bridge is used to access the SoC subsystem CSRs.

	  IO requests are routed to this bus by means of the DW AMBA 3 AXI

	  Interconnect. In case of any APB protocol collisions, slave device

	  not responding on timeout an IRQ is raised with an erroneous address

	  reported to the APB terminator (APB Errors Handler Block). This

	  driver provides the interrupt handler to detect the erroneous

	  address, prints an error message about the address fault, updates an

	  errors counter. The counter and the APB-bus operations timeout can be

	  accessed via corresponding sysfs nodes.



config BT1_AXI

	tristate "Baikal-T1 AXI-bus driver"

	depends on MIPS_BAIKAL_T1 || COMPILE_TEST

drivers/bus/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ obj-$(CONFIG_MOXTET) += moxtet.o 
# DPAA2 fsl-mc bus

obj-$(CONFIG_FSL_MC_BUS)	+= fsl-mc/



obj-$(CONFIG_BT1_APB)		+= bt1-apb.o

obj-$(CONFIG_BT1_AXI)		+= bt1-axi.o

obj-$(CONFIG_IMX_WEIM)		+= imx-weim.o

obj-$(CONFIG_MIPS_CDMM)		+= mips_cdmm.o

drivers/bus/bt1-apb.c

0 → 100644
+422 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only

/*

 * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC

 *

 * Authors:

 *   Serge Semin <Sergey.Semin@baikalelectronics.ru>

 *

 * Baikal-T1 APB-bus driver

 */



#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/types.h>

#include <linux/device.h>

#include <linux/atomic.h>

#include <linux/platform_device.h>

#include <linux/interrupt.h>

#include <linux/nmi.h>

#include <linux/of.h>

#include <linux/regmap.h>

#include <linux/clk.h>

#include <linux/reset.h>

#include <linux/time64.h>

#include <linux/clk.h>

#include <linux/sysfs.h>



#define APB_EHB_ISR			0x00

#define APB_EHB_ISR_PENDING		BIT(0)

#define APB_EHB_ISR_MASK		BIT(1)

#define APB_EHB_ADDR			0x04

#define APB_EHB_TIMEOUT			0x08



#define APB_EHB_TIMEOUT_MIN		0x000003FFU

#define APB_EHB_TIMEOUT_MAX		0xFFFFFFFFU



/*

 * struct bt1_apb - Baikal-T1 APB EHB private data

 * @dev: Pointer to the device structure.

 * @regs: APB EHB registers map.

 * @res: No-device error injection memory region.

 * @irq: Errors IRQ number.

 * @rate: APB-bus reference clock rate.

 * @pclk: APB-reference clock.

 * @prst: APB domain reset line.

 * @count: Number of errors detected.

 */

struct bt1_apb {

	struct device *dev;



	struct regmap *regs;

	void __iomem *res;

	int irq;



	unsigned long rate;

	struct clk *pclk;



	struct reset_control *prst;



	atomic_t count;

};



static const struct regmap_config bt1_apb_regmap_cfg = {

	.reg_bits = 32,

	.val_bits = 32,

	.reg_stride = 4,

	.max_register = APB_EHB_TIMEOUT,

	.fast_io = true

};



static inline unsigned long bt1_apb_n_to_timeout_us(struct bt1_apb *apb, u32 n)

{

	u64 timeout = (u64)n * USEC_PER_SEC;



	do_div(timeout, apb->rate);



	return timeout;



}



static inline unsigned long bt1_apb_timeout_to_n_us(struct bt1_apb *apb,

						    unsigned long timeout)

{

	u64 n = (u64)timeout * apb->rate;



	do_div(n, USEC_PER_SEC);



	return n;



}



static irqreturn_t bt1_apb_isr(int irq, void *data)

{

	struct bt1_apb *apb = data;

	u32 addr = 0;



	regmap_read(apb->regs, APB_EHB_ADDR, &addr);



	dev_crit_ratelimited(apb->dev,

		"APB-bus fault %d: Slave access timeout at 0x%08x\n",

		atomic_inc_return(&apb->count),

		addr);



	/*

	 * Print backtrace on each CPU. This might be pointless if the fault

	 * has happened on the same CPU as the IRQ handler is executed or

	 * the other core proceeded further execution despite the error.

	 * But if it's not, by looking at the trace we would get straight to

	 * the cause of the problem.

	 */

	trigger_all_cpu_backtrace();



	regmap_update_bits(apb->regs, APB_EHB_ISR, APB_EHB_ISR_PENDING, 0);



	return IRQ_HANDLED;

}



static void bt1_apb_clear_data(void *data)

{

	struct bt1_apb *apb = data;

	struct platform_device *pdev = to_platform_device(apb->dev);



	platform_set_drvdata(pdev, NULL);

}



static struct bt1_apb *bt1_apb_create_data(struct platform_device *pdev)

{

	struct device *dev = &pdev->dev;

	struct bt1_apb *apb;

	int ret;



	apb = devm_kzalloc(dev, sizeof(*apb), GFP_KERNEL);

	if (!apb)

		return ERR_PTR(-ENOMEM);



	ret = devm_add_action(dev, bt1_apb_clear_data, apb);

	if (ret) {

		dev_err(dev, "Can't add APB EHB data clear action\n");

		return ERR_PTR(ret);

	}



	apb->dev = dev;

	atomic_set(&apb->count, 0);

	platform_set_drvdata(pdev, apb);



	return apb;

}



static int bt1_apb_request_regs(struct bt1_apb *apb)

{

	struct platform_device *pdev = to_platform_device(apb->dev);

	void __iomem *regs;



	regs = devm_platform_ioremap_resource_byname(pdev, "ehb");

	if (IS_ERR(regs)) {

		dev_err(apb->dev, "Couldn't map APB EHB registers\n");

		return PTR_ERR(regs);

	}



	apb->regs = devm_regmap_init_mmio(apb->dev, regs, &bt1_apb_regmap_cfg);

	if (IS_ERR(apb->regs)) {

		dev_err(apb->dev, "Couldn't create APB EHB regmap\n");

		return PTR_ERR(apb->regs);

	}



	apb->res = devm_platform_ioremap_resource_byname(pdev, "nodev");

	if (IS_ERR(apb->res)) {

		dev_err(apb->dev, "Couldn't map reserved region\n");

		return PTR_ERR(apb->res);

	}



	return 0;

}



static int bt1_apb_request_rst(struct bt1_apb *apb)

{

	int ret;



	apb->prst = devm_reset_control_get_optional_exclusive(apb->dev, "prst");

	if (IS_ERR(apb->prst)) {

		dev_warn(apb->dev, "Couldn't get reset control line\n");

		return PTR_ERR(apb->prst);

	}



	ret = reset_control_deassert(apb->prst);

	if (ret)

		dev_err(apb->dev, "Failed to deassert the reset line\n");



	return ret;

}



static void bt1_apb_disable_clk(void *data)

{

	struct bt1_apb *apb = data;



	clk_disable_unprepare(apb->pclk);

}



static int bt1_apb_request_clk(struct bt1_apb *apb)

{

	int ret;



	apb->pclk = devm_clk_get(apb->dev, "pclk");

	if (IS_ERR(apb->pclk)) {

		dev_err(apb->dev, "Couldn't get APB clock descriptor\n");

		return PTR_ERR(apb->pclk);

	}



	ret = clk_prepare_enable(apb->pclk);

	if (ret) {

		dev_err(apb->dev, "Couldn't enable the APB clock\n");

		return ret;

	}



	ret = devm_add_action_or_reset(apb->dev, bt1_apb_disable_clk, apb);

	if (ret) {

		dev_err(apb->dev, "Can't add APB EHB clocks disable action\n");

		return ret;

	}



	apb->rate = clk_get_rate(apb->pclk);

	if (!apb->rate) {

		dev_err(apb->dev, "Invalid clock rate\n");

		return -EINVAL;

	}



	return 0;

}



static void bt1_apb_clear_irq(void *data)

{

	struct bt1_apb *apb = data;



	regmap_update_bits(apb->regs, APB_EHB_ISR, APB_EHB_ISR_MASK, 0);

}



static int bt1_apb_request_irq(struct bt1_apb *apb)

{

	struct platform_device *pdev = to_platform_device(apb->dev);

	int ret;



	apb->irq = platform_get_irq(pdev, 0);

	if (apb->irq < 0)

		return apb->irq;



	ret = devm_request_irq(apb->dev, apb->irq, bt1_apb_isr, IRQF_SHARED,

			       "bt1-apb", apb);

	if (ret) {

		dev_err(apb->dev, "Couldn't request APB EHB IRQ\n");

		return ret;

	}



	ret = devm_add_action(apb->dev, bt1_apb_clear_irq, apb);

	if (ret) {

		dev_err(apb->dev, "Can't add APB EHB IRQs clear action\n");

		return ret;

	}



	/* Unmask IRQ and clear it' pending flag. */

	regmap_update_bits(apb->regs, APB_EHB_ISR,

			   APB_EHB_ISR_PENDING | APB_EHB_ISR_MASK,

			   APB_EHB_ISR_MASK);



	return 0;

}



static ssize_t count_show(struct device *dev, struct device_attribute *attr,

			  char *buf)

{

	struct bt1_apb *apb = dev_get_drvdata(dev);



	return scnprintf(buf, PAGE_SIZE, "%d\n", atomic_read(&apb->count));

}

static DEVICE_ATTR_RO(count);



static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,

			    char *buf)

{

	struct bt1_apb *apb = dev_get_drvdata(dev);

	unsigned long timeout;

	int ret;

	u32 n;



	ret = regmap_read(apb->regs, APB_EHB_TIMEOUT, &n);

	if (ret)

		return ret;



	timeout = bt1_apb_n_to_timeout_us(apb, n);



	return scnprintf(buf, PAGE_SIZE, "%lu\n", timeout);

}



static ssize_t timeout_store(struct device *dev,

			     struct device_attribute *attr,

			     const char *buf, size_t count)

{

	struct bt1_apb *apb = dev_get_drvdata(dev);

	unsigned long timeout;

	int ret;

	u32 n;



	if (kstrtoul(buf, 0, &timeout) < 0)

		return -EINVAL;



	n = bt1_apb_timeout_to_n_us(apb, timeout);

	n = clamp(n, APB_EHB_TIMEOUT_MIN, APB_EHB_TIMEOUT_MAX);



	ret = regmap_write(apb->regs, APB_EHB_TIMEOUT, n);



	return ret ?: count;

}

static DEVICE_ATTR_RW(timeout);



static ssize_t inject_error_show(struct device *dev, struct device_attribute *attr,

			     char *buf)

{

	return scnprintf(buf, PAGE_SIZE, "Error injection: nodev irq\n");

}



static ssize_t inject_error_store(struct device *dev,

			      struct device_attribute *attr,

			      const char *data, size_t count)

{

	struct bt1_apb *apb = dev_get_drvdata(dev);



	/*

	 * Either dummy read from the unmapped address in the APB IO area

	 * or manually set the IRQ status.

	 */

	if (!strncmp(data, "nodev", 5))

		readl(apb->res);

	else if (!strncmp(data, "irq", 3))

		regmap_update_bits(apb->regs, APB_EHB_ISR, APB_EHB_ISR_PENDING,

				   APB_EHB_ISR_PENDING);

	else

		return -EINVAL;



	return count;

}

static DEVICE_ATTR_RW(inject_error);



static struct attribute *bt1_apb_sysfs_attrs[] = {

	&dev_attr_count.attr,

	&dev_attr_timeout.attr,

	&dev_attr_inject_error.attr,

	NULL

};

ATTRIBUTE_GROUPS(bt1_apb_sysfs);



static void bt1_apb_remove_sysfs(void *data)

{

	struct bt1_apb *apb = data;



	device_remove_groups(apb->dev, bt1_apb_sysfs_groups);

}



static int bt1_apb_init_sysfs(struct bt1_apb *apb)

{

	int ret;



	ret = device_add_groups(apb->dev, bt1_apb_sysfs_groups);

	if (ret) {

		dev_err(apb->dev, "Failed to create EHB APB sysfs nodes\n");

		return ret;

	}



	ret = devm_add_action_or_reset(apb->dev, bt1_apb_remove_sysfs, apb);

	if (ret)

		dev_err(apb->dev, "Can't add APB EHB sysfs remove action\n");



	return ret;

}



static int bt1_apb_probe(struct platform_device *pdev)

{

	struct bt1_apb *apb;

	int ret;



	apb = bt1_apb_create_data(pdev);

	if (IS_ERR(apb))

		return PTR_ERR(apb);



	ret = bt1_apb_request_regs(apb);

	if (ret)

		return ret;



	ret = bt1_apb_request_rst(apb);

	if (ret)

		return ret;



	ret = bt1_apb_request_clk(apb);

	if (ret)

		return ret;



	ret = bt1_apb_request_irq(apb);

	if (ret)

		return ret;



	ret = bt1_apb_init_sysfs(apb);

	if (ret)

		return ret;



	return 0;

}



static const struct of_device_id bt1_apb_of_match[] = {

	{ .compatible = "baikal,bt1-apb" },

	{ }

};

MODULE_DEVICE_TABLE(of, bt1_apb_of_match);



static struct platform_driver bt1_apb_driver = {

	.probe = bt1_apb_probe,

	.driver = {

		.name = "bt1-apb",

		.of_match_table = bt1_apb_of_match

	}

};

module_platform_driver(bt1_apb_driver);



MODULE_AUTHOR("Serge Semin <Sergey.Semin@baikalelectronics.ru>");

MODULE_DESCRIPTION("Baikal-T1 APB-bus driver");

MODULE_LICENSE("GPL v2");

CRA Git | Maintained and supported by SUSTech CRA and CCSE