[PATCH v7 04/12] lib: utils/cache: Add fdt cmo helpers

[Anup Patel]

On Mon, Oct 20, 2025 at 11:56 AM Nick Hu <nick.hu at sifive.com> wrote:
>
> Add the helpers to build up the cache hierarchy via FDT and provide some
> cmo functions for the user who want to flush the entire cache.
>
> Signed-off-by: Nick Hu <nick.hu at sifive.com>
> Reviewed-by: Samuel Holland <samuel.holland at sifive.com>
> Reviewed-by: Anup Patel <anup at brainfault.org>
> ---
>  include/sbi_utils/cache/fdt_cmo_helper.h |  40 +++++++++++
>  lib/utils/cache/fdt_cmo_helper.c         | 112 +++++++++++++++++++++++++++++++
>  lib/utils/cache/objects.mk               |   1 +
>  platform/generic/platform.c              |   3 +-
>  4 files changed, 155 insertions(+), 1 deletion(-)
>
> diff --git a/include/sbi_utils/cache/fdt_cmo_helper.h b/include/sbi_utils/cache/fdt_cmo_helper.h
> new file mode 100644
> index 0000000000000000000000000000000000000000..a6a28db9ede2722d8261d2e077eeb7710cff0893
> --- /dev/null
> +++ b/include/sbi_utils/cache/fdt_cmo_helper.h
> @@ -0,0 +1,40 @@
> +/*
> + * SPDX-License-Identifier: BSD-2-Clause
> + *
> + * Copyright (c) 2025 SiFive Inc.
> + */
> +
> +#ifndef __FDT_CMO_HELPER_H__
> +#define __FDT_CMO_HELPER_H__
> +
> +#ifdef CONFIG_FDT_CACHE
> +/**
> + * Flush the private first level cache of the current hart
> + *
> + * @return 0 on success, or a negative error code on failure
> + */
> +int fdt_cmo_private_flc_flush_all(void);
> +
> +/**
> + * Flush the last level cache of the current hart
> + *
> + * @return 0 on success, or a negative error code on failure
> + */
> +int fdt_cmo_llc_flush_all(void);
> +
> +/**
> + * Initialize the cache devices for each hart
> + *
> + * @param fdt devicetree blob
> + * @param cold_boot cold init or warm init
> + *
> + * @return 0 on success, or a negative error code on failure
> + */
> +int fdt_cmo_init(bool cold_boot);
> +
> +#else
> +
> +static inline int fdt_cmo_init(bool cold_boot) { return 0; }
> +
> +#endif /* CONFIG_FDT_CACHE */
> +#endif /* __FDT_CMO_HELPER_H__ */
> diff --git a/lib/utils/cache/fdt_cmo_helper.c b/lib/utils/cache/fdt_cmo_helper.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..6d2e853dd735735092c57db2398f97a64de3ab5e
> --- /dev/null
> +++ b/lib/utils/cache/fdt_cmo_helper.c
> @@ -0,0 +1,112 @@
> +/*
> + * SPDX-License-Identifier: BSD-2-Clause
> + *
> + * Copyright (c) 2025 SiFive Inc.
> + */
> +
> +#include <libfdt.h>
> +#include <sbi/sbi_error.h>
> +#include <sbi/sbi_scratch.h>
> +#include <sbi_utils/cache/fdt_cache.h>
> +#include <sbi_utils/cache/fdt_cmo_helper.h>
> +#include <sbi_utils/fdt/fdt_helper.h>
> +
> +static unsigned long flc_offset;
> +
> +#define get_hart_flc(_s) \
> +       sbi_scratch_read_type(_s, struct cache_device *, flc_offset)
> +#define set_hart_flc(_s, _p) \
> +       sbi_scratch_write_type(_s, struct cache_device *, flc_offset, _p)
> +
> +int fdt_cmo_private_flc_flush_all(void)
> +{
> +       struct cache_device *flc = get_hart_flc(sbi_scratch_thishart_ptr());
> +
> +       if (!flc || !flc->cpu_private)
> +               return SBI_ENODEV;
> +
> +       return cache_flush_all(flc);
> +}
> +
> +int fdt_cmo_llc_flush_all(void)
> +{
> +       struct cache_device *llc = get_hart_flc(sbi_scratch_thishart_ptr());
> +
> +       if (!llc)
> +               return SBI_ENODEV;
> +
> +       while (llc->next)
> +               llc = llc->next;
> +
> +       return cache_flush_all(llc);
> +}
> +
> +static int fdt_cmo_cold_init(const void *fdt)
> +{
> +       struct sbi_scratch *scratch;
> +       struct cache_device *dev;
> +       int cpu_offset, cpus_offset, rc;
> +       u32 hartid;
> +
> +       cpus_offset = fdt_path_offset(fdt, "/cpus");
> +       if (cpus_offset < 0)
> +               return SBI_EINVAL;
> +
> +       fdt_for_each_subnode(cpu_offset, fdt, cpus_offset) {
> +               rc = fdt_parse_hart_id(fdt, cpu_offset, &hartid);
> +               if (rc)
> +                       continue;
> +
> +               scratch = sbi_hartid_to_scratch(hartid);
> +               if (!scratch)
> +                       continue;
> +
> +               rc = fdt_next_cache_get(fdt, cpu_offset, &dev);
> +               if (rc)
> +                       return rc;

The "next-level-cache" property might be absent in CPU DT nodes
so fdt_next_cache_get() must return SBI_ENOENT when it is
absent.

Also, over here we must handle "rc == SBI_ENOENT" as special
case as follows:

diff --git a/lib/utils/cache/fdt_cmo_helper.c b/lib/utils/cache/fdt_cmo_helper.c
index 6d2e853d..d87bab76 100644
--- a/lib/utils/cache/fdt_cmo_helper.c
+++ b/lib/utils/cache/fdt_cmo_helper.c
@@ -62,8 +62,10 @@ static int fdt_cmo_cold_init(const void *fdt)
                        continue;

                rc = fdt_next_cache_get(fdt, cpu_offset, &dev);
-               if (rc)
+               if (rc && rc != SBI_ENOENT)
                        return rc;
+               if (rc == SBI_ENOENT)
+                       dev = NULL;

                set_hart_flc(scratch, dev);
        }

I will take care of the above at the time of merging this series.

Regards,
Anup