Re: [PATCH v8 2/5] soc: qcom: Add SoC sleep stats driver

[Maulik Shah]

Hi,

On 5/27/2021 5:15 AM, Stephen Boyd wrote:
> Quoting Maulik Shah (2021-05-21 04:26:08)
> > diff --git a/drivers/soc/qcom/soc_sleep_stats.c b/drivers/soc/qcom/soc_sleep_stats.c
> > new file mode 100644
> > index 0000000..a8396f9
> > --- /dev/null
> > +++ b/drivers/soc/qcom/soc_sleep_stats.c
> > @@ -0,0 +1,255 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (c) 2011-2021, The Linux Foundation. All rights reserved.
> > + */
> > +
> > +#include <linux/debugfs.h>
> > +#include <linux/device.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/seq_file.h>
> > +
> > +#include <linux/soc/qcom/smem.h>
> > +#include <clocksource/arm_arch_timer.h>
> > +
> > +#define STAT_TYPE_OFFSET       0x0
> > +#define COUNT_OFFSET           0x4
> > +#define LAST_ENTERED_AT_OFFSET 0x8
> > +#define LAST_EXITED_AT_OFFSET  0x10
> > +#define ACCUMULATED_OFFSET     0x18
> > +#define CLIENT_VOTES_OFFSET    0x1c
> > +
> > +struct subsystem_data {
> > +       const char *name;
> > +       u32 smem_item;
> > +       u32 pid;
> > +};
> > +
> > +static const struct subsystem_data subsystems[] = {
> > +       { "modem", 605, 1 },
> > +       { "wpss", 605, 13 },
> > +       { "adsp", 606, 2 },
> > +       { "cdsp", 607, 5 },
> > +       { "slpi", 608, 3 },
> > +       { "gpu", 609, 0 },
> > +       { "display", 610, 0 },
> > +       { "adsp_island", 613, 2 },
> > +       { "slpi_island", 613, 3 },
> > +};
> > +
> > +struct stats_config {
> > +       size_t offset_addr;
> > +       size_t num_records;
> > +       bool appended_stats_avail;
> > +};
> > +
> > +struct stats_data {
> > +       bool appended_stats_avail;
> > +       void __iomem *base;
> > +};
> > +
> > +struct sleep_stats {
> > +       u32 stat_type;
> > +       u32 count;
> > +       u64 last_entered_at;
> > +       u64 last_exited_at;
> > +       u64 accumulated;
> Is this coming from memory directly? So we need a bunch of __le32 and
> __le64 markings and then the endian swaps?
Its stored in AOP (RPMH)/ RPM msgram for SoC sleep stats and individual 
subsystem stats stored in SMEM.
> > +};
> > +
> > +struct appended_stats {
> > +       u32 client_votes;
> > +       u32 reserved[3];
> This one too? It's stored in smem?
Its only stored in RPM msgram. RPMH and SMEM do not have it.
> > +};
> > +
> > +static void qcom_print_stats(struct seq_file *s, const struct sleep_stats *stat)
> > +{
> > +       u64 accumulated = stat->accumulated;
> > +       /*
> > +        * If a subsystem is in sleep when reading the sleep stats adjust
> > +        * the accumulated sleep duration to show actual sleep time.
> > +        */
> > +       if (stat->last_entered_at > stat->last_exited_at)
> > +               accumulated += arch_timer_read_counter() - stat->last_entered_at;
> Doesn't this read the virtual count? Which could be very different than
> the physical count that the subsystems see and then write into smem? I
> suppose we need some sort of "physical count" reading API to match up
> the timestamps that are there but that is sort of hard given that the
> physical count isn't always intended to be read by the kernel. Maybe we
> should split off an MMIO architected timer to be used by this code that
> uses the same clocksource that the other subsystems are using?
The timer used is same across all subsystems. Beside it try to give more 
accurate information by modifying
total sleep length if subsytem is staying in sleep.
> > +
> > +       seq_printf(s, "Count: %u\n", stat->count);
> > +       seq_printf(s, "Last Entered At: %llu\n", stat->last_entered_at);
> > +       seq_printf(s, "Last Exited At: %llu\n", stat->last_exited_at);
> > +       seq_printf(s, "Accumulated Duration: %llu\n", accumulated);
> > +}
> > +
> > +static int qcom_subsystem_sleep_stats_show(struct seq_file *s, void *unused)
> > +{
> > +       struct subsystem_data *subsystem = s->private;
> > +       struct sleep_stats *stat;
> > +
> > +       /* Items are allocated lazily, so lookup pointer each time */
> > +       stat = qcom_smem_get(subsystem->pid, subsystem->smem_item, NULL);
> > +       if (IS_ERR(stat))
> > +               return PTR_ERR(stat);
> Can this return EPROBE_DEFER to userspace? That would be pretty weird.
> Maybe we should convert the return value to -EIO regardless of the error.
Ok. Updated in v9 to return -EIO.
> > +
> > +       qcom_print_stats(s, stat);
> > +
> > +       return 0;
> > +}
> > +
> > +static int qcom_soc_sleep_stats_show(struct seq_file *s, void *unused)
> > +{
> > +       struct stats_data *d = s->private;
> > +       void __iomem *reg = d->base;
> > +       struct sleep_stats stat;
> > +
> > +       memcpy_fromio(&stat, reg, sizeof(stat));
> > +       qcom_print_stats(s, &stat);
> > +
> > +       if (d->appended_stats_avail) {
> > +               struct appended_stats votes;
> > +
> > +               memcpy_fromio(&votes, reg + CLIENT_VOTES_OFFSET, sizeof(votes));
> > +               seq_printf(s, "Client Votes: %#x\n", votes.client_votes);
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +DEFINE_SHOW_ATTRIBUTE(qcom_soc_sleep_stats);
> > +DEFINE_SHOW_ATTRIBUTE(qcom_subsystem_sleep_stats);
> > +
> > +static void qcom_create_soc_sleep_stat_files(struct dentry *root, void __iomem *reg,
> > +                                            struct stats_data *d, u32 num_records)
> > +{
> > +       char stat_type[sizeof(u32) + 1] = {0};
> > +       u32 offset = 0, type;
> > +       int i, j;
> > +
> > +       for (i = 0; i < num_records; i++) {
> > +               d[i].base = reg + offset;
> > +
> > +               /*
> > +                * Read the low power mode name and create debugfs file for it.
> What do we do if there are two same named low power modes? Maybe they
> should be directories instead with pretty name and values inside of
> them.

This is agreed between AOP and Linux kernel so we would not have two or 
more same named low power modes.

This applies to many things like the structure defination which also be 
agreed and AOP/subsytems populates same

structure in MSGRAM / SMEM respectively which kernel can read in same 
format.

> > +                * The names read could be of below,
> > +                * (may change depending on low power mode supported).
> > +                * For rpmh-sleep-stats: "aosd", "cxsd" and "ddr".
> > +                * For rpm-sleep-stats: "vmin" and "vlow".
> > +                */
> > +               type = readl(d[i].base);
> > +               for (j = 0; j < sizeof(u32); j++) {
> > +                       stat_type[j] = type & 0xff;
> > +                       type = type >> 8;
> > +               }
> > +               strim(stat_type);
> > +               debugfs_create_file(stat_type, 0400, root, &d[i],
> > +                                   &qcom_soc_sleep_stats_fops);
> > +
> > +               offset += sizeof(struct sleep_stats);
> > +               if (d[i].appended_stats_avail)
> > +                       offset += sizeof(struct appended_stats);
> > +       }
> > +}
> > +
> > +static void qcom_create_subsystem_stat_files(struct dentry *root)
> > +{
> > +       struct sleep_stats *stat;
> const? The pointer isn't used though so is this even relevant?
Changed to const.
> > +       int i;
> > +
> > +       for (i = 0; i < ARRAY_SIZE(subsystems); i++) {
> > +               stat = qcom_smem_get(subsystems[i].pid, subsystems[i].smem_item, NULL);
> > +               if (IS_ERR(stat))
> > +                       continue;
> > +
> > +               debugfs_create_file(subsystems[i].name, 0400, root, (void *)&subsystems[i],
> Do we need to cast to void pointer? Is it unused? If it's unused then
> pass NULL?
It is used. It needs cast too since subsystems array is already a const, 
without cast will compiler will complain discarding const.
> > +                                   &qcom_subsystem_sleep_stats_fops);
> > +       }
> > +}
> > +
> > +static int qcom_soc_sleep_stats_probe(struct platform_device *pdev)
> > +{
> > +       struct resource *res;
> > +       void __iomem *reg;
> > +       void __iomem *offset_addr;
> > +       phys_addr_t stats_base;
> > +       resource_size_t stats_size;
> > +       struct dentry *root;
> > +       const struct stats_config *config;
> > +       struct stats_data *d;
> > +       int i;
> > +
> > +       config = device_get_match_data(&pdev->dev);
> > +       if (!config)
> > +               return -ENODEV;
> > +
> > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +       if (!res)
> > +               return PTR_ERR(res);
> > +
> > +       offset_addr = ioremap(res->start + config->offset_addr, sizeof(u32));
> Why can't we devm_platform_get_and_ioremap_resource()?
Ok, updated in v9.
> > +       if (IS_ERR(offset_addr))
> > +               return PTR_ERR(offset_addr);
> > +
> > +       stats_base = res->start | readl_relaxed(offset_addr);
> > +       stats_size = resource_size(res);
> > +       iounmap(offset_addr);
> Oh because of unmap? Can we add a resource for stats_base/size to the
> system? I'd really like to see what address that is at.
Ok it was developed like this since AOP can populate the stat at 
different address and it gives this address when reading the value at 
offset.
> I think it is
> actually within the same region of this "pointer" that is assigned in
> DT, but I honestly don't know why we wouldn't just hardcode the address
> in DT to begin with instead of doing this map, find the real address,
> and then map that. Is this really changing that often?

yes its in the same region. it generally don't change for single target 
but prone to change for other targets.

I have hardcoded that address it self in DT to start with and removed 
the offset part from driver.

>   Probably it
> changes a few times during development but then it settles down and we
> can just hardcode it in DT? At least please make a resource and reserve
> it so we know that the region isn't being used by other kernel drivers.
>
> > +
> > +       reg = devm_ioremap(&pdev->dev, stats_base, stats_size);
> > +       if (!reg)
> > +               return -ENOMEM;
> > +
> > +       d = devm_kcalloc(&pdev->dev, config->num_records,
> > +                        sizeof(*d), GFP_KERNEL);
> > +       if (!d)
> > +               return -ENOMEM;
> > +
> > +       for (i = 0; i < config->num_records; i++)
> > +               d[i].appended_stats_avail = config->appended_stats_avail;
> > +
> > +       root = debugfs_create_dir("qcom_sleep_stats", NULL);
> > +
> > +       qcom_create_subsystem_stat_files(root);
> > +       qcom_create_soc_sleep_stat_files(root, reg, d, config->num_records);
> > +
> > +       platform_set_drvdata(pdev, root);
> > +
> > +       return 0;
> > +}
> > +
> > +static int qcom_soc_sleep_stats_remove(struct platform_device *pdev)
> > +{
> > +       struct dentry *root = platform_get_drvdata(pdev);
> > +
> > +       debugfs_remove_recursive(root);
> > +
> > +       return 0;
> > +}
> > +
> > +static const struct stats_config rpm_data = {
> > +       .offset_addr = 0x14,
> > +       .num_records = 2,
> > +       .appended_stats_avail = true,
> > +};
> > +
> > +static const struct stats_config rpmh_data = {
> > +       .offset_addr = 0x4,
> > +       .num_records = 3,
> > +       .appended_stats_avail = false,
> > +};
> > +
> > +static const struct of_device_id qcom_soc_sleep_stats_table[] = {
> > +       { .compatible = "qcom,rpm-sleep-stats", .data = &rpm_data },
> > +       { .compatible = "qcom,rpmh-sleep-stats", .data = &rpmh_data },
> > +       { }
> > +};
> > +
> > +static struct platform_driver soc_sleep_stats_driver = {
> A driver seems pretty heavyweight for a thing that sticks stuff into
> debugfs. It's not "driving" anything.

Removed the driver from the end.

Thanks,
Maulik

> > +       .probe = qcom_soc_sleep_stats_probe,
> > +       .remove = qcom_soc_sleep_stats_remove,
> > +       .driver = {
> > +               .name = "soc_sleep_stats",
> > +               .of_match_table = qcom_soc_sleep_stats_table,
> > +       },
> > +};
> > +module_platform_driver(soc_sleep_stats_driver);
> > +
> > +MODULE_DESCRIPTION("Qualcomm Technologies, Inc. (QTI) SoC Sleep Stats driver");
> > +MODULE_LICENSE("GPL v2");
> > +MODULE_SOFTDEP("pre: smem");

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