Re: [PATCH v5 2/3] EDAC/cadence: Add Cadence DDR EDAC driver

[Borislav Petkov <bp@alien8.de>]

On Mon, Oct 05, 2026 at 02:49:23PM +0200, Paul Louvel wrote:
> diff --git a/drivers/edac/Makefile b/drivers/edac/Makefile
> index a37534300ab9..0d66a072b15c 100644
> --- a/drivers/edac/Makefile
> +++ b/drivers/edac/Makefile
> @@ -82,6 +82,7 @@ obj-$(CONFIG_EDAC_SYNOPSYS)		+= synopsys_edac.o
>  obj-$(CONFIG_EDAC_XGENE)		+= xgene_edac.o
>  obj-$(CONFIG_EDAC_TI)			+= ti_edac.o
>  obj-$(CONFIG_EDAC_QCOM)			+= qcom_edac.o
> +obj-$(CONFIG_EDAC_CADENCE)		+= cadence_edac.o

This goes at the end of that file.

>  obj-$(CONFIG_EDAC_ASPEED)		+= aspeed_edac.o
>  obj-$(CONFIG_EDAC_BLUEFIELD)		+= bluefield_edac.o
>  obj-$(CONFIG_EDAC_DMC520)		+= dmc520_edac.o
> diff --git a/drivers/edac/cadence_edac.c b/drivers/edac/cadence_edac.c
> new file mode 100644
> index 000000000000..26b9a7facd57
> --- /dev/null
> +++ b/drivers/edac/cadence_edac.c
> @@ -0,0 +1,399 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright 2015 Renesas Electronics Europe Ltd.
> + * Copyright 2026 Bootlin
> + *
> + * Based on highbank EDAC driver:
> + *
> + * Copyright 2011-2012 Calxeda, Inc.
> + */
> +
> +#include <linux/bits.h>
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/edac.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/mm.h>
> +#include <linux/of_address.h>
> +#include <linux/string.h>
> +#include <linux/spinlock.h>
> +#include <linux/platform_device.h>

How many of those includes are *actually* needed?

> +#include "edac_mc.h"
> +#include "edac_module.h"
> +
> +#define DRV_NAME "cdns_edac"

"cadence_edac" is a perfectly fine name.

> +#define REG_BYTE_SZ 4
> +#define DDR_CTL(n) ((n) * REG_BYTE_SZ)
> +
> +#define CDNS_DDR_DDR_STAT DDR_CTL(0)

Align all defines vertically like this:

#define REG_BYTE_SZ		4
#define DDR_CTL(n)		((n) * REG_BYTE_SZ)

#define CDNS_DDR_DDR_STAT	DDR_CTL(0)
...

> +#define CDNS_DDR_DDR_STAT_DRAM_CLASS GENMASK_U32(11, 8)
> +#define CDNS_DDR_DDR_STAT_DRAM_DDR2 BIT(2)
> +#define CDNS_DDR_DDR_STAT_GET_DRAM_CLASS(reg) FIELD_GET(CDNS_DDR_DDR_STAT_DRAM_CLASS, reg)

Also, I would shorten those long mouthfuls so that the code remains relatively
readable. The "DDR_DDR" thing above is the first I'd whack. And so on.

> +#define CDNS_DDR_ECC_STAT DDR_CTL(36)
> +#define CDNS_DDR_ECC_STAT_ENABLED BIT(16)
> +#define CDNS_DDR_ECC_STAT_IS_ENABLED(reg) FIELD_GET(CDNS_DDR_ECC_STAT_ENABLED, reg)
> +#define CDNS_DDR_ECC_STAT_FWC BIT(24)
> +
> +#define CDNS_DDR_ECC_XOR DDR_CTL(37)
> +#define CDNS_DDR_ECC_XOR_CHECK_BITS GENMASK_U32(13, 0)
> +
> +#define CDNS_DDR_BUS_CTRL DDR_CTL(54)
> +#define CDNS_DDR_BUS_CTRL_REDUC BIT(1)
> +
> +/* DDR Controller Error Registers */
> +
> +#define CDNS_DDR_ECC_U_ERR_ADDR DDR_CTL(38)
> +#define CDNS_DDR_ECC_U_ERR_STAT DDR_CTL(39)
> +
> +#define CDNS_DDR_ECC_C_ERR_ADDR DDR_CTL(41)
> +#define CDNS_DDR_ECC_C_ERR_STAT DDR_CTL(42)
> +
> +#define CDNS_DDR_ECC_ERR_STAT_GET_SYNDROME(reg) FIELD_GET(GENMASK(6, 0), reg)
> +
> +#define CDNS_DDR_PORT_CMD_ERR_ADDR DDR_CTL(61)
> +#define CDNS_DDR_PORT_CMD_ERR_TYPE DDR_CTL(62)
> +#define CDNS_DDR_PORT_CMD_ERR_TYPE_GET(reg) FIELD_GET(GENMASK_U32(10, 8), reg)
> +
> +/* DDR Controller Interrupt Registers */
> +
> +#define CDNS_DDR_ECC_INT_STAT DDR_CTL(56)
> +#define CDNS_DDR_ECC_INT_STAT_CE BIT(3)
> +#define CDNS_DDR_ECC_INT_STAT_MULTIPLE_CE BIT(4)
> +#define CDNS_DDR_ECC_INT_STAT_UE BIT(5)
> +#define CDNS_DDR_ECC_INT_STAT_MULTIPLE_UE BIT(6)
> +#define CDNS_DDR_ECC_INT_STAT_PORT_CMD_CHAN BIT(7)
> +
> +#define CDNS_DDR_ECC_INT_ACK DDR_CTL(57)
> +#define CDNS_DDR_ECC_INT_ACK_MASK GENMASK_U32(21, 0)
> +
> +#define CDNS_DDR_ECC_INT_CTRL DDR_CTL(58)
> +#define CDNS_DDR_ECC_INT_CTRL_MASK GENMASK_U32(21, 0)
> +#define CDNS_DDR_ECC_INT_CTRL_MASK_ALL BIT(22)
> +#define CDNS_DDR_ECC_INT_CTRL_UNMASK(i) ((~(i)) & CDNS_DDR_ECC_INT_CTRL_MASK)
> +
> +struct cdns_mc_priv {

For all privately used struct names and static functions, drop the "cdns_"
namespace prefix - it is not necessary.

> +	int irq;
> +	void __iomem *io_base;
> +	struct dentry *debugfs;
> +	spinlock_t lock;
> +	u16 xor_check_bits;
> +};
> +
> +static irqreturn_t cdns_mc_err_handler(int irq, void *dev_id)
> +{
> +	struct mem_ctl_info *mci = dev_id;
> +	struct cdns_mc_priv *priv = mci->pvt_info;
> +	u32 addr, status, err_addr, syndrome, reg;
> +	char other_details_str[32];
> +	u8 type;
> +
> +	/* Read the interrupt status register */

The fact that you have to put an obvious comment above the read of a register
basically says that your register naming is not optimal enough. If you name it
properly, you don't need a comment.

> +	status = readl(priv->io_base + CDNS_DDR_ECC_INT_STAT);
> +	if (!status)
> +		return IRQ_NONE;
> +
> +	/*
> +	 * We can't know how many CE / UE occurred since last ACK in case of

Please use passive voice: no "we" or "I", etc, and describe things in an
imperative mood.

> +	 * multiple errors. Just report it.
> +	 */
> +
> +	if ((status & CDNS_DDR_ECC_INT_STAT_UE) || (status & CDNS_DDR_ECC_INT_STAT_MULTIPLE_UE)) {

This is what I mean with too long lines. That one and others like it needs
shortening.

Also this test can be merged into a single one by ORing the flags.

> +		reg = readl(priv->io_base + CDNS_DDR_ECC_U_ERR_STAT);
> +		syndrome = CDNS_DDR_ECC_ERR_STAT_GET_SYNDROME(reg);
> +
> +		err_addr = readl(priv->io_base + CDNS_DDR_ECC_U_ERR_ADDR);
> +
> +		edac_mc_handle_error(HW_EVENT_ERR_UNCORRECTED, mci, 1, err_addr >> PAGE_SHIFT,
> +				     err_addr & ~PAGE_MASK, syndrome, 0, 0, -1, mci->ctl_name, "");
> +	}

ditto for that one below:

> +	if ((status & CDNS_DDR_ECC_INT_STAT_CE) || (status & CDNS_DDR_ECC_INT_STAT_MULTIPLE_CE)) {
> +		reg = readl(priv->io_base + CDNS_DDR_ECC_C_ERR_STAT);
> +		syndrome = CDNS_DDR_ECC_ERR_STAT_GET_SYNDROME(reg);
> +
> +		err_addr = readl(priv->io_base + CDNS_DDR_ECC_C_ERR_ADDR);
> +
> +		edac_mc_handle_error(HW_EVENT_ERR_CORRECTED, mci, 1, err_addr >> PAGE_SHIFT,
> +				     err_addr & ~PAGE_MASK, syndrome, 0, 0, -1, mci->ctl_name, "");
> +	}
> +
> +	if (status & CDNS_DDR_ECC_INT_STAT_PORT_CMD_CHAN) {

What kind of an error is that one so that you have to call
edac_mc_handle_error() for it separately?

> +		addr = readl(priv->io_base + CDNS_DDR_PORT_CMD_ERR_ADDR);
> +		reg = readl(priv->io_base + CDNS_DDR_PORT_CMD_ERR_TYPE);
> +		type = CDNS_DDR_PORT_CMD_ERR_TYPE_GET(reg);
> +
> +		snprintf(other_details_str, sizeof(other_details_str), "type 0x%02x", type);
> +
> +		edac_mc_handle_error(HW_EVENT_ERR_INFO, mci, 1, addr >> PAGE_SHIFT,
> +				     addr & ~PAGE_MASK, 0, 0, 0, -1, mci->ctl_name,
> +				     other_details_str);
> +	}
> +
> +	/* clear the error, clears the interrupt */

No need for obvious comments. Audit your whole driver pls.

> +	writel(status & CDNS_DDR_ECC_INT_ACK_MASK, priv->io_base + CDNS_DDR_ECC_INT_ACK);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int cdns_get_mem_sz(resource_size_t *mem_sz)

Do not use an I/O function param but return the correct size or an error and
have call site handle that.

Looking how that function is called only once, simply merge it into the call
site.

> +{
> +	struct device_node *np;
> +	struct resource res;
> +	int ret;
> +
> +	np = of_find_node_by_name(NULL, "memory");
> +	if (!np)
> +		return -ENODEV;
> +
> +	ret = of_address_to_resource(np, 0, &res);
> +
> +	of_node_put(np);
> +
> +	if (ret)
> +		return ret;
> +
> +	*mem_sz = resource_size(&res);
> +
> +	return 0;
> +}

> +
> +#ifdef CONFIG_EDAC_DEBUG
> +
> +static void cdns_rmw(struct cdns_mc_priv *priv, u32 reg, u32 mask, u32 val)
> +{
> +	u32 regval;
> +
> +	regval = readl(priv->io_base + reg);
> +	regval &= ~mask;
> +	regval |= (val << __bf_shf(mask)) & mask;
> +	writel(regval, priv->io_base + reg);
> +}
> +
> +static ssize_t cdns_force_ecc_error(struct file *file, const char __user *data, size_t count,
> +				    loff_t *ppos)
> +{
> +	struct device *dev = file->private_data;
> +	struct mem_ctl_info *mci = to_mci(dev);
> +	struct cdns_mc_priv *priv = mci->pvt_info;
> +
> +	spin_lock(&priv->lock);
> +
> +	cdns_rmw(priv, CDNS_DDR_ECC_XOR, CDNS_DDR_ECC_XOR_CHECK_BITS, priv->xor_check_bits);
> +	cdns_rmw(priv, CDNS_DDR_ECC_STAT, CDNS_DDR_ECC_STAT_FWC, 1);
> +
> +	spin_unlock(&priv->lock);
> +
> +	return count;
> +}
> +
> +static const struct file_operations cdns_ecc_error_fops = {
> +	.open = simple_open,
> +	.write = cdns_force_ecc_error,
> +	.llseek = generic_file_llseek,
> +};

#else
static ssize_t cdns_force_ecc_error(struct file *file, const char __user *data, size_t count, loff_t *ppos)
{
	return 0
}
#endif

and get rid of the ifdeffery below.

> +static void cdns_setup_debugfs(struct mem_ctl_info *mci)
> +{
> +	struct cdns_mc_priv *priv = mci->pvt_info;
> +
> +	priv->debugfs = edac_debugfs_create_dir(DRV_NAME);
> +	if (!priv->debugfs) {
> +		dev_dbg(mci->pdev, "failed to create debugfs dir\n");
> +		return;
> +	}
> +
> +	edac_debugfs_create_x16("bits", 0644, priv->debugfs, &priv->xor_check_bits);
> +	edac_debugfs_create_file("inject", 0200, priv->debugfs, &mci->dev, &cdns_ecc_error_fops);
> +}
> +
> +#endif

...

> +
> +	/*
> +	 * Unmask ECC recoverable and unrecoverable interrupts, and port
> +	 * command errors.
> +	 */
> +	writel(CDNS_DDR_ECC_INT_CTRL_UNMASK(
> +		       CDNS_DDR_ECC_INT_STAT_CE | CDNS_DDR_ECC_INT_STAT_MULTIPLE_CE |
> +		       CDNS_DDR_ECC_INT_STAT_UE | CDNS_DDR_ECC_INT_STAT_MULTIPLE_UE |
> +		       CDNS_DDR_ECC_INT_STAT_PORT_CMD_CHAN),

Yah, unreadable mess that. Shorten pls.

> +	       io_base + CDNS_DDR_ECC_INT_CTRL);
> +
> +	return 0;
> +}

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette