Re: [PATCH 1/3] soc: sifive: Add SiFive private L2 cache support

[Eric Lin]

Hi Ben,

On Fri, Jun 16, 2023 at 4:30 PM Ben Dooks <ben.dooks@xxxxxxxxxxxxxxx> wrote:
>
> On 16/06/2023 07:32, Eric Lin wrote:
> > This adds SiFive private L2 cache driver which will show
> > cache config information when booting and add cpu hotplug
> > callback functions.
> >
> > Signed-off-by: Eric Lin <eric.lin@xxxxxxxxxx>
> > Signed-off-by: Nick Hu <nick.hu@xxxxxxxxxx>
> > Reviewed-by: Zong Li <zong.li@xxxxxxxxxx>
> > ---
> >   drivers/soc/sifive/Kconfig            |   8 +
> >   drivers/soc/sifive/Makefile           |   1 +
> >   drivers/soc/sifive/sifive_pl2.h       |  25 ++++
> >   drivers/soc/sifive/sifive_pl2_cache.c | 202 ++++++++++++++++++++++++++
> >   include/linux/cpuhotplug.h            |   1 +
> >   5 files changed, 237 insertions(+)
> >   create mode 100644 drivers/soc/sifive/sifive_pl2.h
> >   create mode 100644 drivers/soc/sifive/sifive_pl2_cache.c
> >
> > diff --git a/drivers/soc/sifive/Kconfig b/drivers/soc/sifive/Kconfig
> > index e86870be34c9..573564295058 100644
> > --- a/drivers/soc/sifive/Kconfig
> > +++ b/drivers/soc/sifive/Kconfig
> > @@ -7,4 +7,12 @@ config SIFIVE_CCACHE
> >       help
> >         Support for the composable cache controller on SiFive platforms.
> >
> > +config SIFIVE_PL2
> > +     bool "Sifive private L2 Cache controller"
> > +     help
> > +       Support for the private L2 cache controller on SiFive platforms.
> > +       The SiFive Private L2 Cache Controller is per hart and communicates
> > +       with both the upstream L1 caches and downstream L3 cache or memory,
> > +       enabling a high-performance cache subsystem.
> > +
> >   endif
> > diff --git a/drivers/soc/sifive/Makefile b/drivers/soc/sifive/Makefile
> > index 1f5dc339bf82..707493e1c691 100644
> > --- a/drivers/soc/sifive/Makefile
> > +++ b/drivers/soc/sifive/Makefile
> > @@ -1,3 +1,4 @@
> >   # SPDX-License-Identifier: GPL-2.0
> >
> >   obj-$(CONFIG_SIFIVE_CCACHE) += sifive_ccache.o
> > +obj-$(CONFIG_SIFIVE_PL2)     += sifive_pl2_cache.o
> > diff --git a/drivers/soc/sifive/sifive_pl2.h b/drivers/soc/sifive/sifive_pl2.h
> > new file mode 100644
> > index 000000000000..57aa1019d5ed
> > --- /dev/null
> > +++ b/drivers/soc/sifive/sifive_pl2.h
> > @@ -0,0 +1,25 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (C) 2023 SiFive, Inc.
> > + *
> > + */
> > +
> > +#ifndef _SIFIVE_PL2_H
> > +#define _SIFIVE_PL2_H
> > +
> > +#define SIFIVE_PL2_CONFIG1_OFFSET    0x1000
> > +#define SIFIVE_PL2_CONFIG0_OFFSET    0x1008
> > +#define SIFIVE_PL2_PMCLIENT_OFFSET   0x2800
> > +
> > +struct sifive_pl2_state {
> > +     void __iomem *pl2_base;
> > +     u32 config1;
> > +     u32 config0;
> > +     u64 pmclientfilter;
> > +};
> > +
> > +int sifive_pl2_pmu_init(void);
> > +int sifive_pl2_pmu_probe(struct device_node *pl2_node,
> > +                      void __iomem *pl2_base, int cpu);
> > +
> > +#endif /*_SIFIVE_PL2_H */
> > diff --git a/drivers/soc/sifive/sifive_pl2_cache.c b/drivers/soc/sifive/sifive_pl2_cache.c
> > new file mode 100644
> > index 000000000000..aeb51d576af9
> > --- /dev/null
> > +++ b/drivers/soc/sifive/sifive_pl2_cache.c
> > @@ -0,0 +1,202 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * SiFive private L2 cache controller Driver
> > + *
> > + * Copyright (C) 2018-2023 SiFive, Inc.
> > + */
> > +
> > +#define pr_fmt(fmt) "pL2CACHE: " fmt
> > +
> > +#include <linux/of.h>
> > +#include <linux/of_device.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/io.h>
> > +#include <linux/cpu_pm.h>
> > +#include <linux/cpuhotplug.h>
> > +#include "sifive_pl2.h"
> > +
> > +static DEFINE_PER_CPU(struct sifive_pl2_state, sifive_pl2_state);
> > +
> > +static void sifive_pl2_state_save(struct sifive_pl2_state *pl2_state)
> > +{
> > +     void __iomem *pl2_base = pl2_state->pl2_base;
> > +
> > +     if (!pl2_base)
> > +             return;
>
> is this test realy needed?
>

Yes,
The function cpuhp_setup_state() is called before sifive_pl2_cache_dev_probe().
When registering the CPU hotplug state, the kernel will issue the pl2
CPU hotplug callback.
However, the pl2_base is not yet being ioremap in sifive_pl2_cache_dev_probe().
Therefore, it is necessary to check pl2_base first to avoid such a scenario.

> > +
> > +     pl2_state->config1 = readl(pl2_base + SIFIVE_PL2_CONFIG1_OFFSET);
> > +     pl2_state->config0 = readl(pl2_base + SIFIVE_PL2_CONFIG0_OFFSET);
> > +     pl2_state->pmclientfilter = readq(pl2_base + SIFIVE_PL2_PMCLIENT_OFFSET);
> > +}
> > +
> > +static void sifive_pl2_state_restore(struct sifive_pl2_state *pl2_state)
> > +{
> > +     void __iomem *pl2_base = pl2_state->pl2_base;
> > +
> > +     if (!pl2_base)
> > +             return;
> > +
> > +     writel(pl2_state->config1, pl2_base + SIFIVE_PL2_CONFIG1_OFFSET);
> > +     writel(pl2_state->config0, pl2_base + SIFIVE_PL2_CONFIG0_OFFSET);
> > +     writeq(pl2_state->pmclientfilter, pl2_base + SIFIVE_PL2_PMCLIENT_OFFSET);
> > +}
> > +
> > +/*
> > + * CPU Hotplug call back function
> > + */
> > +static int sifive_pl2_online_cpu(unsigned int cpu)
> > +{
> > +     struct sifive_pl2_state *pl2_state = this_cpu_ptr(&sifive_pl2_state);
> > +
> > +     sifive_pl2_state_restore(pl2_state);
> > +
> > +     return 0;
> > +}
> > +
> > +static int sifive_pl2_offline_cpu(unsigned int cpu)
> > +{
> > +     struct sifive_pl2_state *pl2_state = this_cpu_ptr(&sifive_pl2_state);
> > +
> > +     /* Save the pl2 state */
> > +     sifive_pl2_state_save(pl2_state);
> > +
> > +     return 0;
> > +}
> > +
> > +/*
> > + *  PM notifer for suspend to ram
> > + */
> > +#ifdef CONFIG_CPU_PM
> > +static int sifive_pl2_pm_notify(struct notifier_block *b, unsigned long cmd,
> > +                             void *v)
> > +{
> > +     struct sifive_pl2_state *pl2_state = this_cpu_ptr(&sifive_pl2_state);
> > +
> > +     switch (cmd) {
> > +     case CPU_PM_ENTER:
> > +             /* Save the pl2 state */
> > +             sifive_pl2_state_save(pl2_state);
> > +             break;
> > +     case CPU_PM_ENTER_FAILED:
> > +     case CPU_PM_EXIT:
> > +             sifive_pl2_state_restore(pl2_state);
> > +             break;
> > +     default:
> > +             break;
> > +     }
> > +
> > +     return NOTIFY_OK;
> > +}
> > +
> > +static struct notifier_block sifive_pl2_pm_notifier_block = {
> > +     .notifier_call = sifive_pl2_pm_notify,
> > +};
> > +
> > +static inline void sifive_pl2_pm_init(void)
> > +{
> > +     cpu_pm_register_notifier(&sifive_pl2_pm_notifier_block);
> > +}
> > +
> > +#else
> > +static inline void sifive_pl2_pm_init(void) { }
> > +#endif /* CONFIG_CPU_PM */
> > +
> > +static const struct of_device_id sifive_pl2_cache_of_ids[] = {
> > +     { .compatible = "sifive,pL2Cache0" },
> > +     { .compatible = "sifive,pL2Cache1" },
>
> why the single cap here? I think that looks ugly.
>

OK, I'll fix it in v2.

> > +     { /* sentinel value */ }
> > +};
> > +
> > +static void pl2_config_read(void __iomem *pl2_base, int cpu)
> > +{
> > +     u32 regval, bank, way, set, cacheline;
> > +
> > +     regval = readl(pl2_base);
> > +     bank = regval & 0xff;
> > +     pr_info("in the CPU: %d\n", cpu);
> > +     pr_info("No. of Banks in the cache: %d\n", bank);
> > +     way = (regval & 0xff00) >> 8;
> > +     pr_info("No. of ways per bank: %d\n", way);
> > +     set = (regval & 0xff0000) >> 16;
> > +     pr_info("Total sets: %llu\n", (uint64_t)1 << set);
> > +     cacheline = (regval & 0xff000000) >> 24;
> > +     pr_info("Bytes per cache block: %llu\n", (uint64_t)1 << cacheline);
> > +     pr_info("Size: %d\n", way << (set + cacheline));
>
>
> please either remove this or make it a single line, this is just going
> to spam the log with any system with more than one cpu core.
>

OK, I will make this log more simple in v2.
Thanks for the review.

Best Regards,
Eric Lin.

> > +}
> > +
> > +static int sifive_pl2_cache_dev_probe(struct platform_device *pdev)
> > +{
> > +     struct resource *res;
> > +     int cpu, ret = -EINVAL;
> > +     struct device_node *cpu_node, *pl2_node;
> > +     struct sifive_pl2_state *pl2_state = NULL;
> > +     void __iomem *pl2_base;
> > +
> > +     /* Traverse all cpu nodes to find the one mapping to its pl2 node. */
> > +     for_each_cpu(cpu, cpu_possible_mask) {
> > +             cpu_node = of_cpu_device_node_get(cpu);
> > +             pl2_node = of_parse_phandle(cpu_node, "next-level-cache", 0);
> > +
> > +             /* Found it! */
> > +             if (dev_of_node(&pdev->dev) == pl2_node) {
> > +                     /* Use cpu to get its percpu data sifive_pl2_state. */
> > +                     pl2_state = per_cpu_ptr(&sifive_pl2_state, cpu);
> > +                     break;
> > +             }
> > +     }
> > +
> > +     if (!pl2_state) {
> > +             pr_err("Not found the corresponding cpu_node in dts.\n");
> > +             goto early_err;
> > +     }
> > +
> > +     /* Set base address of select and counter registers. */
> > +     pl2_base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
> > +     if (IS_ERR(pl2_base)) {
> > +             ret = PTR_ERR(pl2_base);
> > +             goto early_err;
> > +     }
> > +
> > +     /* Print pL2 configs. */
> > +     pl2_config_read(pl2_base, cpu);
> > +     pl2_state->pl2_base = pl2_base;
> > +
> > +     return 0;
> > +
> > +early_err:
> > +     return ret;
> > +}
> > +
> > +static struct platform_driver sifive_pl2_cache_driver = {
> > +     .driver = {
> > +                .name = "SiFive-pL2-cache",
> > +                .of_match_table = sifive_pl2_cache_of_ids,
> > +                },
> > +     .probe = sifive_pl2_cache_dev_probe,
> > +};
> > +
> > +static int __init sifive_pl2_cache_init(void)
> > +{
> > +     int ret;
> > +
> > +     ret = cpuhp_setup_state(CPUHP_AP_RISCV_SIFIVE_PL2_ONLINE,
> > +                             "soc/sifive/pl2:online",
> > +                                   sifive_pl2_online_cpu,
> > +                                   sifive_pl2_offline_cpu);
> > +     if (ret < 0) {
> > +             pr_err("Failed to register CPU hotplug notifier %d\n", ret);
> > +             return ret;
> > +     }
> > +
> > +     ret = platform_driver_register(&sifive_pl2_cache_driver);
> > +     if (ret) {
> > +             pr_err("Failed to register sifive_pl2_cache_driver: %d\n", ret);
> > +             return ret;
> > +     }
> > +
> > +     sifive_pl2_pm_init();
> > +
> > +     return ret;
> > +}
> > +
> > +device_initcall(sifive_pl2_cache_init);
> > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> > index 0f1001dca0e0..35cd5ba0030b 100644
> > --- a/include/linux/cpuhotplug.h
> > +++ b/include/linux/cpuhotplug.h
> > @@ -207,6 +207,7 @@ enum cpuhp_state {
> >       CPUHP_AP_IRQ_AFFINITY_ONLINE,
> >       CPUHP_AP_BLK_MQ_ONLINE,
> >       CPUHP_AP_ARM_MVEBU_SYNC_CLOCKS,
> > +     CPUHP_AP_RISCV_SIFIVE_PL2_ONLINE,
> >       CPUHP_AP_X86_INTEL_EPB_ONLINE,
> >       CPUHP_AP_PERF_ONLINE,
> >       CPUHP_AP_PERF_X86_ONLINE,
>
> --
> Ben Dooks                               http://www.codethink.co.uk/
> Senior Engineer                         Codethink - Providing Genius
>
> https://www.codethink.co.uk/privacy.html
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