linux-kernel - Re: [PATCH v7 1/3] edac: Add support for Amazon's Annapurna Labs L1 EDAC

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Message-ID: <0bd30915-71ca-cba2-f273-f7a1ff6d5a8d@amazon.com>
Date:   Mon, 20 Jan 2020 16:41:51 +0200
From:   "Hawa, Hanna" <hhhawa@...zon.com>
To:     James Morse <james.morse@....com>, <Sudeep.Holla@....com>
CC:     <bp@...en8.de>, <mchehab@...nel.org>, <mark.rutland@....com>,
        <robh+dt@...nel.org>, <frowand.list@...il.com>,
        <davem@...emloft.net>, <gregkh@...uxfoundation.org>,
        <linus.walleij@...aro.org>, <daniel@...earbox.net>,
        <paulmck@...ux.ibm.com>, <linux-kernel@...r.kernel.org>,
        <linux-edac@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <dwmw@...zon.co.uk>, <benh@...zon.com>, <ronenk@...zon.com>,
        <talel@...zon.com>, <jonnyc@...zon.com>, <hanochu@...zon.com>
Subject: Re: [PATCH v7 1/3] edac: Add support for Amazon's Annapurna Labs L1
 EDAC



On 1/15/2020 8:49 PM, James Morse wrote:
> Hi Hanna,
> 
> (This was still on my list. I've not seen a newer version, its not in next, and it still
> applies, so:)

Thank you.

> 
> On 15/10/2019 13:09, Hanna Hawa wrote:
>> Adds support for Amazon's Annapurna Labs L1 EDAC driver to detect and
>> report L1 errors.
> 
>> diff --git a/drivers/edac/al_l1_edac.c b/drivers/edac/al_l1_edac.c
>> new file mode 100644
>> index 000000000000..e363a80b4d13
>> --- /dev/null
>> +++ b/drivers/edac/al_l1_edac.c
>> @@ -0,0 +1,190 @@
> 
>> +#include <asm/sysreg.h>
>> +#include <linux/bitfield.h>
>> +#include <linux/of.h>
>> +#include <linux/smp.h>
> 
> You need <linux/platform_device.h> for platform_device_register_simple().

Will be added in next PS.

> 
> [...]
> 
>> +static void al_l1_edac_cpumerrsr_read_status(void *arg)
>> +{
> 
>> +	for (i = 0; i < repeat; i++) {
>> +		if (fatal)
>> +			edac_device_handle_ue(edac_dev, 0, 0, msg);
>> +		else
>> +			edac_device_handle_ce(edac_dev, 0, 0, msg);
>> +	}
> 
> What serialises these? You kick this off from on_each_cpu(), what stops two CPUs calling
> this at the same time? 'edac_dev->counters.ce_count += count;' will go wrong in this case.
> 
> I think you need a spinlock around the edac_device_* calls that take edac_dev so that only
> one occurs at a time.

Agree with you, will add spinlock in next PS.

> 
> 
>> +}
>> +
>> +static void al_l1_edac_check(struct edac_device_ctl_info *edac_dev)
>> +{
>> +	on_each_cpu(al_l1_edac_cpumerrsr_read_status, edac_dev, 1);
>> +}
>> +
>> +static int al_l1_edac_probe(struct platform_device *pdev)
>> +{
>> +	struct edac_device_ctl_info *edac_dev;
>> +	struct device *dev = &pdev->dev;
>> +	int ret;
>> +
>> +	edac_dev = edac_device_alloc_ctl_info(0, DRV_NAME, 1, "L", 1, 1, NULL,
>> +					      0, edac_device_alloc_index());
>> +	if (!edac_dev)
>> +		return -ENOMEM;
>> +
>> +	edac_dev->edac_check = al_l1_edac_check;
>> +	edac_dev->dev = dev;
>> +	edac_dev->mod_name = DRV_NAME;
>> +	edac_dev->dev_name = dev_name(dev);
>> +	edac_dev->ctl_name = "L1_cache";
>> +	platform_set_drvdata(pdev, edac_dev);
>> +
>> +	ret = edac_device_add_device(edac_dev);
>> +	if (ret)
>> +		goto err;
>> +
>> +	return 0;
>> +err:
> 
> (this goto has one user, meaning you can remove it by restructuring the code)

Will be fixed in next PS.

> 
> 
>> +	dev_err(dev, "Failed to add L1 edac device (%d)\n", ret);
>> +	edac_device_free_ctl_info(edac_dev);
>> +
>> +	return ret;
>> +}
>> +
> 
>> +static const struct of_device_id al_l1_edac_of_match[] = {
>> +	{ .compatible = "al,alpine-v2" },
>> +	{ .compatible = "amazon,alpine-v3" },
>> +	{}
>> +};
> 
> Unusually these are machine compatibles. It may be worth a comment that these are the
> platforms which are known to have Cortex-A57/A72 configured with this support, and access
> to the registers enabled by firmware.

Will be added.

> 
> 
>> +MODULE_DEVICE_TABLE(of, al_l1_edac_of_match);
> 
> [..]
> 
>> +static int __init al_l1_init(void)
>> +{
>> +	struct device_node *root = of_find_node_by_path("/");
>> +	int ret;
> 
> root could be NULL here.

Will be fixed.

> 
> 
>> +	if (!of_match_node(al_l1_edac_of_match, root))
>> +		return 0;
>> +
>> +	ret = platform_driver_register(&al_l1_edac_driver);
>> +	if (ret) {
>> +		pr_err("Failed to register %s (%d)\n", DRV_NAME, ret);
>> +		return ret;
>> +	}
>> +
>> +	edac_l1_device = platform_device_register_simple(DRV_NAME, -1, NULL, 0);
>> +	if (IS_ERR(edac_l1_device)) {
>> +		pr_err("Failed to register EDAC AL L1 platform device\n");
>> +		return PTR_ERR(edac_l1_device);
>> +	}
>> +
>> +	return 0;
>> +}
> 
> With the edac_device_handle_ce() race fixed:
> Reviewed-by: James Morse <james.morse@....com>

Thanks,
Hanna

> 
> 
> Thanks,
> 
> James
>