Date:   Thu, 19 Sep 2019 11:36:06 +0300
From:   "Shenhar, Talel" <talel@...zon.com>
To:     James Morse <james.morse@....com>
CC:     <robh+dt@...nel.org>, <mark.rutland@....com>, <bp@...en8.de>,
        <mchehab@...nel.org>, <davem@...emloft.net>,
        <gregkh@...uxfoundation.org>, <nicolas.ferre@...rochip.com>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-edac@...r.kernel.org>, <dwmw@...zon.co.uk>,
        <benh@...nel.crashing.org>, <hhhawa@...zon.com>,
        <ronenk@...zon.com>, <jonnyc@...zon.com>, <hanochu@...zon.com>,
        <amirkl@...zon.com>, <barakw@...zon.com>
Subject: Re: [PATCH v2 2/2] EDAC: al-mc-edac: Introduce Amazon's Annapurna
 Labs Memory Controller EDAC

Thanks for the review.


On 9/18/2019 8:47 PM, James Morse wrote:
> Hi Talel,
>
> On 15/09/2019 07:43, Talel Shenhar wrote:
>> The Amazon's Annapurna Labs Memory Controller EDAC supports ECC capability
>> for error detection and correction (Single bit error correction, Double
>> detection). This driver introduces EDAC driver for that capability.
> Is there any documentation for this memory controller?
Unfortunately, we don't have public documentation for it.
>
>
>> diff --git a/drivers/edac/al_mc_edac.c b/drivers/edac/al_mc_edac.c
>> new file mode 100644
>> index 0000000..f9763d4
>> --- /dev/null
>> +++ b/drivers/edac/al_mc_edac.c
>> @@ -0,0 +1,382 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
>> + */
>> +#include <linux/bitfield.h>
> #include <linux/bitops.h> for hweight_long()

shall be part of v3.

btw: do you use some tool to catch those missing includes?

>
>> +#include <linux/edac.h>
>> +#include <linux/of_irq.h>
> #include <linux/platform_device.h> for platform_get_resource()
shall be part of v3.
>
>> +#include "edac_module.h"
>> +/* Registers Values */
>> +#define AL_MC_MSTR_DEV_CFG_X4	0
>> +#define AL_MC_MSTR_DEV_CFG_X8	1
>> +#define AL_MC_MSTR_DEV_CFG_X16	2
>> +#define AL_MC_MSTR_DEV_CFG_X32	3
>> +#define AL_MC_MSTR_RANKS_MAX 4
> Is this a fixed property of the memory controller, or is it a limit imposed from somewhere
> else. (Does it need to come from the DT?)

Yes. this is a fixed behavior hence not part of dt.

>
>
>> +#define AL_MC_MSTR_DATA_BUS_WIDTH_X64	0
>> +
>> +#define DRV_NAME "al_mc_edac"
>> +#define AL_MC_EDAC_MSG_MAX 256
>> +#define AL_MC_EDAC_MSG(message, buffer_size, type,			\
>> +		       rank, row, bg, bank, column, syn0, syn1, syn2)	\
>> +	snprintf(message, buffer_size,					\
>> +		 "%s rank=0x%x row=0x%x bg=0x%x bank=0x%x col=0x%x "	\
>> +		 "syn0: 0x%x syn1: 0x%x syn2: 0x%x",			\
>> +		 type == HW_EVENT_ERR_UNCORRECTED ? "UE" : "CE",	\
>> +		 rank, row, bg, bank, column, syn0, syn1, syn2)
>> +
>> +struct al_mc_edac {
>> +	void __iomem *mmio_base;
>> +	int irq_ce;
>> +	int irq_ue;
>> +};
>> +
>> +static int al_mc_edac_handle_ce(struct mem_ctl_info *mci)
>> +{
>> +	struct al_mc_edac *al_mc = mci->pvt_info;
>> +	u32 eccerrcnt;
>> +	u16 ce_count;
>> +	u32 ecccaddr0;
>> +	u32 ecccaddr1;
>> +	u32 ecccsyn0;
>> +	u32 ecccsyn1;
>> +	u32 ecccsyn2;
>> +	u8 rank;
>> +	u32 row;
>> +	u8 bg;
>> +	u8 bank;
>> +	u16 column;
>> +	char msg[AL_MC_EDAC_MSG_MAX];
> (Some of these could go on the same line, same with UE below)
Shall be part of v3
> +
> +	edac_mc_handle_error(HW_EVENT_ERR_CORRECTED, mci,
> +			     ce_count, 0, 0, 0, 0, 0, -1, mci->ctl_name, msg);
> You used active_ranks as the layer size in al_mc_edac_probe(). Can't you supply the rank here?
>
> (If its not useful, why is it setup like this in al_mc_edac_probe()?)

Seems it can be removed from probe.

Shall be part of v3.

>
>
> +	u8 bank;
> +	u16 column;
> +	char msg[AL_MC_EDAC_MSG_MAX];
> +
> +	eccerrcnt = readl_relaxed(al_mc->mmio_base + AL_MC_ECC_ERR_COUNT);
> +	ue_count = FIELD_GET(AL_MC_ECC_ERR_COUNT_UE, eccerrcnt);
> +	if (!ue_count)
> +		return 0;
> +
> +	eccuaddr0 = readl_relaxed(al_mc->mmio_base + AL_MC_ECC_UE_ADDR0);
> +	eccuaddr1 = readl_relaxed(al_mc->mmio_base + AL_MC_ECC_UE_ADDR1);
> +	eccusyn0 = readl_relaxed(al_mc->mmio_base + AL_MC_ECC_UE_SYND0);
> +	eccusyn1 = readl_relaxed(al_mc->mmio_base + AL_MC_ECC_UE_SYND1);
> +	eccusyn2 = readl_relaxed(al_mc->mmio_base + AL_MC_ECC_UE_SYND2);
> +
> +	writel(AL_MC_ECC_CLEAR_UE_COUNT | AL_MC_ECC_CLEAR_UE_ERR,
> +	       al_mc->mmio_base + AL_MC_ECC_CLEAR);
> +
> +	dev_dbg(mci->pdev, "eccuaddr0=0x%08x eccuaddr1=0x%08x\n",
> +		eccuaddr0, eccuaddr1);
> +
> +	rank = FIELD_GET(AL_MC_ECC_UE_ADDR0_RANK, eccuaddr0);
> +	row = FIELD_GET(AL_MC_ECC_UE_ADDR0_ROW, eccuaddr0);
> +
> +	bg = FIELD_GET(AL_MC_ECC_UE_ADDR1_BG, eccuaddr1);
> +	bank = FIELD_GET(AL_MC_ECC_UE_ADDR1_BANK, eccuaddr1);
> +	column = FIELD_GET(AL_MC_ECC_UE_ADDR1_COLUMN, eccuaddr1);
> +
> +	AL_MC_EDAC_MSG(msg, sizeof(msg), HW_EVENT_ERR_UNCORRECTED,
> +		       rank, row, bg, bank, column,
> +		       eccusyn0, eccusyn1, eccusyn2);
> +
> +	edac_mc_handle_error(HW_EVENT_ERR_UNCORRECTED, mci,
> +			     ue_count, 0, 0, 0, 0, 0, -1, mci->ctl_name, msg);
>
> What happens when this code runs at the same time as the corrected error handler calling
> edac_mc_handler_error() with this same mci?
>
> This could happen on a second CPU, or on one cpu if the corrected handler is polled.
>
> edac_mc_handle_error() memset's the edac_raw_error_desc in mci, so it can't be called in
> parallel, or twice on the same cpu.
>
> I think you need an irqsave spinlock around the calls to edac_mc_handle_error().

shall add locks in v3.

>
>> +
>> +static irqreturn_t al_mc_edac_irq_handler_ue(int irq, void *info)
>> +{
>> +	struct platform_device *pdev = info;
>> +	struct mem_ctl_info *mci = platform_get_drvdata(pdev);
>> +	int ue_count;
>> +
>> +	ue_count = al_mc_edac_handle_ue(mci);
>> +	if (ue_count)
>> +		return IRQ_HANDLED;
>> +	else
>> +		return IRQ_NONE;
>> +}
> As you don't use ue_count, wouldn't this be clearer:
>
> | if (al_mc_edac_handle_ue(mci))
> | 	return IRQ_HANDLED;
> | return IRQ_NONE;
>
> ?
ack, shall add to v3
>
>> +static int al_mc_edac_probe(struct platform_device *pdev)
>> +{
>> +	struct resource *resource;
>> +	void __iomem *mmio_base;
>> +	unsigned int active_ranks;
>> +	struct edac_mc_layer layers[1];
>> +	struct mem_ctl_info *mci;
>> +	struct al_mc_edac *al_mc;
>> +	int ret;
>> +
>> +	resource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> platform_get_resource() can fail, returning NULL.
ack, shall add to v3
>
>
> +
> +	if (al_mc->irq_ue > 0) {
> +		ret = devm_request_irq(&pdev->dev,
> +				       al_mc->irq_ue,
> +				       al_mc_edac_irq_handler_ue,
>> +				       0,
> As you know when your device has triggered the interrupt from the error counter, could
> these be IRQF_SHARED?
ack, shall add to v3
>
>> +static int al_mc_edac_remove(struct platform_device *pdev)
>> +{
>> +	struct mem_ctl_info *mci = platform_get_drvdata(pdev);
>> +
>> +	edac_mc_del_mc(&pdev->dev);
>> +	edac_mc_free(mci);
> What stops your interrupt firing here? You've free'd the memory it uses.
>
> I think you need to devm_free_irq() the interrupts before you free the memory.
ack, shall add to v3
>
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_AUTHOR("Talel Shenhar");
>> +MODULE_DESCRIPTION("Amazon's Annapurna Lab's Memory Controller EDAC Driver");
> (Kconfig says this is 'bool', so it can't be built as a module, having these is a bit odd)

ack, shall add to v3

while at it, shall consider changing to trisate so it can really be 
build as a module as well.

>
>
>
> Thanks,
>
> James

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