Re: [PATCH 2/2] drivers: edac: Add EDAC support for Kryo CPU caches

Sai Prakash Ranjan
2020-01-13T05:44:46Z

Hi Boris,

Thanks for the review comments.

On 2019-12-30 17:20, Borislav Petkov wrote:
> On Thu, Dec 05, 2019 at 09:53:18AM +0000, Sai Prakash Ranjan wrote:
>> Kryo{3,4}XX CPU cores implement RAS extensions to support
>> Error Correcting Code(ECC). Currently all Kryo{3,4}XX CPU
>> cores (gold/silver a.k.a big/LITTLE) support ECC via RAS.
>
> via RAS what? ARM64_RAS_EXTN?
>
> In any case, this needs James to look at and especially if there's some
> ARM-generic functionality in there which should be shared, of course.
>

Yes it is ARM64_RAS_EXTN and I have been hoping if James can provide the
feedback,
it has been some time now since I posted this out.

>> This adds an interrupt based driver for those CPUs and
>
> s/This adds/Add/
>

Will correct.

>> +
>> +config EDAC_QCOM_KRYO_POLL
>> + depends on EDAC_QCOM_KRYO
>> + bool "Poll on Kryo ECC registers"
>> + help
>> + This option chooses whether or not you want to poll on the Kryo
>> ECC
>> + registers. When this is enabled, the polling rate can be set as a
>> + module parameter. By default, it will call the polling function
>> every
>> + second.
>
> Why is this a separate option and why should people use that?
>
> Can the polling/irq be switched automatically?
>

No it cannot be switched automatically. It is used in case some SoCs do
not support an irq based mechanism for EDAC.
But I am contradicting myself because I am telling that atleast one
interrupt should be specified in bindings,
so it is best if I drop this polling option for now.

>> +
>> config EDAC_ASPEED
>> tristate "Aspeed AST 2500 SoC"
>> depends on MACH_ASPEED_G5
>> diff --git a/drivers/edac/Makefile b/drivers/edac/Makefile
>> index d77200c9680b..29edcfa6ec0e 100644
>> --- a/drivers/edac/Makefile
>> +++ b/drivers/edac/Makefile
>> @@ -85,5 +85,6 @@ 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_QCOM_KRYO) += qcom_kryo_edac.o
>
> What is the difference between this new driver and the qcom_edac one?
> Can
> functionality be shared?
>
> Should this new one be called simply kryo_edac instead?
>

qcom_edac driver is for QCOM system cache(last level cache), it should
be renamed to qcom_llcc_edac.c.
This new driver is for QCOM Kryo CPU core caches(L1,L2,L3).

Functionality cannot be shared as these two are different IP blocks and
best kept separate.

>> +
>> +#define DRV_NAME "qcom_kryo_edac"
>> +
>> +/*
>> + * ARM Cortex-A55, Cortex-A75, Cortex-A76 TRM Chapter B3.3
>
> Chapter? Where? URL?
>

I chose this because these TRMs are openly available and if you search
for these above terms like
"Cortex-A76 TRM Chapter B3.3" in google, then the first search result
will be the TRM pdf, otherwise
I would have to specify the long URL for the pdf and we do not know how
long that URL link will be active.

>> +
>> +static const struct error_type err_type[] = {
>> + { edac_device_handle_ce, "Kryo L1 Corrected Error" },
>> + { edac_device_handle_ue, "Kryo L1 Uncorrected Error" },
>> + { edac_device_handle_ue, "Kryo L1 Deferred Error" },
>> + { edac_device_handle_ce, "Kryo L2 Corrected Error" },
>> + { edac_device_handle_ue, "Kryo L2 Uncorrected Error" },
>> + { edac_device_handle_ue, "Kryo L2 Deferred Error" },
>> + { edac_device_handle_ce, "L3 Corrected Error" },
>> + { edac_device_handle_ue, "L3 Uncorrected Error" },
>> + { edac_device_handle_ue, "L3 Deferred Error" },
>> +};
>> +
>
> All that is not really needed - you can put the whole error type
> detection and dumping in kryo_check_err_type() in nicely readable
> switch-case statement. No need for the function pointers and special
> structs.
>

How is this not easily readable? If I put this in kryo_check_err_type,
then
there will be nested switch which I think is not so great in terms of
readability
since it will not fit in one screen and is just more lines of code.

>> +static struct edac_device_ctl_info __percpu *edac_dev;
>> +static struct edac_device_ctl_info *drv_edev_ctl;
>> +
>> +static const char *get_error_msg(u64 errxstatus)
>> +{
>> + const struct error_record *rec;
>> + u32 errxstatus_serr;
>> +
>> + errxstatus_serr = FIELD_GET(KRYO_ERRXSTATUS_SERR, errxstatus);
>> +
>> + for (rec = serror_record; rec->error_code; rec++) {
>> + if (errxstatus_serr == rec->error_code)
>> + return rec->error_msg;
>> + }
>> +
>> + return NULL;
>> +}
>> +
>> +static void dump_syndrome_reg(int error_type, int level,
>> + u64 errxstatus, u64 errxmisc,
>> + struct edac_device_ctl_info *edev_ctl)
>> +{
>> + char msg[KRYO_EDAC_MSG_MAX];
>> + const char *error_msg;
>> + int cpu;
>> +
>> + cpu = raw_smp_processor_id();
>
> Why raw_?
>

Because we will be calling smp_processor_id in preemptible context and
if we enable CONFIG_DEBUG_PREEMPT,
we would get a nice backtrace.

[ 3.747468] BUG: using smp_processor_id() in preemptible [00000000]
code: swapper/0/1
[ 3.755527] caller is qcom_kryo_edac_probe+0x138/0x2b8
[ 3.760819] CPU: 2 PID: 1 Comm: swapper/0 Tainted: G S
5.4.0-rc7-next-20191113-00009-g8666855d6a5b-dirty #107
[ 3.772323] Hardware name: Qualcomm Technologies, Inc. SM8150 MTP
(DT)
[ 3.779030] Call trace:
[ 3.781556] dump_backtrace+0x0/0x158
[ 3.785331] show_stack+0x14/0x20
[ 3.788741] dump_stack+0xb0/0xf4
[ 3.792164] debug_smp_processor_id+0xd8/0xe0
[ 3.796639] qcom_kryo_edac_probe+0x138/0x2b8
[ 3.801116] platform_drv_probe+0x50/0xa8
[ 3.805236] really_probe+0x108/0x360
[ 3.808999] driver_probe_device+0x58/0x100
[ 3.813304] device_driver_attach+0x6c/0x78
[ 3.817606] __driver_attach+0xb0/0xf0
[ 3.821459] bus_for_each_dev+0x68/0xc8
[ 3.825407] driver_attach+0x20/0x28
[ 3.829083] bus_add_driver+0x160/0x1f0
[ 3.833030] driver_register+0x60/0x110
[ 3.836976] __platform_driver_register+0x40/0x48
[ 3.841813] qcom_kryo_edac_driver_init+0x18/0x20
[ 3.846645] do_one_initcall+0x58/0x1a0
[ 3.850596] kernel_init_freeable+0x19c/0x240
[ 3.855075] kernel_init+0x10/0x108
[ 3.858665] ret_from_fork+0x10/0x1c

>> +static int kryo_l1_l2_setup_irq(struct platform_device *pdev,
>> + struct edac_device_ctl_info *edev_ctl)
>> +{
>> + int cpu, errirq, faultirq, ret;
>> +
>> + edac_dev = devm_alloc_percpu(&pdev->dev, *edac_dev);
>> + if (!edac_dev)
>> + return -ENOMEM;
>> +
>> + for_each_possible_cpu(cpu) {
>> + preempt_disable();
>> + per_cpu(edac_dev, cpu) = edev_ctl;
>> + preempt_enable();
>> + }
>
> That sillyness doesn't belong here, if at all.
>

Sorry but I do not understand the sillyness here. Could you please
explain?

> ...
>
>> +static void kryo_poll_cache_error(struct edac_device_ctl_info
>> *edev_ctl)
>> +{
>> + if (!edev_ctl)
>> + edev_ctl = drv_edev_ctl;
>
> That's silly.
>

Actually its not silly. In case, polling is enabled and on PM exit
edev_ctl could be NULL.

>> +
>> + on_each_cpu(kryo_check_l1_l2_ecc, edev_ctl, 1);
>> + kryo_check_l3_scu_ecc(edev_ctl);
>> +}
>
> ...
>
>> +static int qcom_kryo_edac_probe(struct platform_device *pdev)
>> +{
>> + struct edac_device_ctl_info *edev_ctl;
>> + struct device *dev = &pdev->dev;
>> + int ret;
>> +
>> + qcom_kryo_edac_setup();
>
> This function needs to have a return value saying whether it did setup
> the hw properly or not and the probe function needs to return here if
> not.

Ok will add a return check.

Thanks,
Sai