linux-kernel - Re: [PATCH v4 2/2] Loongarch: EDAC driver for loongson memory controller

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Message-ID: <20240913101137.GHZuQP2WzlkvJ5gG2F@fat_crate.local>
Date: Fri, 13 Sep 2024 12:11:37 +0200
From: Borislav Petkov <bp@...en8.de>
To: Zhao Qunqin <zhaoqunqin@...ngson.cn>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	chenhuacai@...nel.org, linux-edac@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...0n.name, tony.luck@...el.com, james.morse@....com,
	mchehab@...nel.org, rric@...nel.org, loongarch@...ts.linux.dev
Subject: Re: [PATCH v4 2/2] Loongarch: EDAC driver for loongson memory
 controller

On Mon, Sep 09, 2024 at 11:21:24AM +0800, Zhao Qunqin wrote:
> Subject: Re: [PATCH v4 2/2] Loongarch: EDAC driver for loongson memory controller

			EDAC/loongson: Add EDAC driver ...

> Reports single bit errors (CE) only.
> 
> Signed-off-by: Zhao Qunqin <zhaoqunqin@...ngson.cn>
> ---

...

> diff --git a/drivers/edac/loongson_edac.c b/drivers/edac/loongson_edac.c
> new file mode 100644
> index 000000000..b89d6e0e7
> --- /dev/null
> +++ b/drivers/edac/loongson_edac.c
> @@ -0,0 +1,182 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2024 Loongson Technology Corporation Limited.
> + */
> +
> +#include <linux/edac.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/platform_device.h>
> +
> +#include "edac_module.h"
> +
> +enum ecc_index {
> +	ECC_SET = 0,
> +	ECC_RESERVED,
> +	ECC_COUNT,
> +	ECC_CS_COUNT,
> +	ECC_CODE,
> +	ECC_ADDR,
> +	ECC_DATA0,
> +	ECC_DATA1,
> +	ECC_DATA2,
> +	ECC_DATA3,
> +};
> +
> +struct loongson_edac_pvt {
> +	u64 *ecc_base;
> +	int last_ce_count;
> +};
> +
> +static void loongson_update_ce_count(struct mem_ctl_info *mci,

Drop the loongson_ prefix from all static functions.

Also, align function arguments on the opening brace.

> +					int chan,
> +					int new)
> +{
> +	int add;
> +	struct loongson_edac_pvt *pvt = mci->pvt_info;

The EDAC tree preferred ordering of variable declarations at the
beginning of a function is reverse fir tree order::

	struct long_struct_name *descriptive_name;
	unsigned long foo, bar;
	unsigned int tmp;
	int ret;

The above is faster to parse than the reverse ordering::

	int ret;
	unsigned int tmp;
	unsigned long foo, bar;
	struct long_struct_name *descriptive_name;

And even more so than random ordering::

	unsigned long foo, bar;
	int ret;
	struct long_struct_name *descriptive_name;
	unsigned int tmp;

> +
> +	add = new - pvt->last_ce_count;
> +
> +	/* Store the new value */

Drop all those obvious comments.

> +	pvt->last_ce_count = new;
> +
> +	/* device resume or any other exceptions*/

No clue what that means.

Also,  the check goes right under the assignment.

> +	if (add < 0)
> +		return;
> +
> +	/*updated the edac core */

Useless comment.

> +	if (add != 0) {

	if (!add)
		return;

and now you can save yourself an indentation level:

	edac_mc_...(

> +		edac_mc_handle_error(HW_EVENT_ERR_CORRECTED, mci, add,
> +					0, 0, 0,
> +					chan, 0, -1, "error", "");
> +		edac_mc_printk(mci, KERN_INFO, "add: %d", add);
> +	}
> +}
> +
> +static int loongson_read_ecc(struct mem_ctl_info *mci)
> +{
> +	u64 ecc;
> +	int cs = 0;
> +	struct loongson_edac_pvt *pvt = mci->pvt_info;
> +
> +	if (!pvt->ecc_base)
> +		return pvt->last_ce_count;
> +
> +	ecc = pvt->ecc_base[ECC_CS_COUNT];
> +	cs += ecc & 0xff;		// cs0
> +	cs += (ecc >> 8) & 0xff;	// cs1
> +	cs += (ecc >> 16) & 0xff;	// cs2
> +	cs += (ecc >> 24) & 0xff;	// cs3

No side comments pls - put them over the line.

> +
> +	return cs;
> +}
> +
> +static void loongson_edac_check(struct mem_ctl_info *mci)
> +{
> +	loongson_update_ce_count(mci, 0, loongson_read_ecc(mci));

Drop this silly wrapper.

> +}
> +
> +static int get_dimm_config(struct mem_ctl_info *mci)
> +{
> +	u32 size, npages;
> +	struct dimm_info *dimm;
> +
> +	/* size not used */
> +	size = -1;
> +	npages = MiB_TO_PAGES(size);
> +
> +	dimm = edac_get_dimm(mci, 0, 0, 0);
> +	dimm->nr_pages = npages;
> +	snprintf(dimm->label, sizeof(dimm->label),
> +			"MC#%uChannel#%u_DIMM#%u",
> +			mci->mc_idx, 0, 0);

Align arguments on the opening brace.

> +	dimm->grain = 8;
> +
> +	return 0;
> +}

...


-- 
Regards/Gruss,
    Boris.

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