[1/2] common: fdt: Add a function for reserving memory without kernel linear mapping

The intent is to reserve memory _and_ prevent it from being included
in the kernel's linear map. For thos reason it is also necessary to include the
'no-map' property for this reserved-mem node.

>From Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt:

no-map (optional) - empty property
    - Indicates the operating system must not create a virtual mapping
      of the region as part of its standard mapping of system memory,
      nor permit speculative access to it under any circumstances other
      than under the control of the device driver using the region.

Signed-off-by: Michael Trimarchi <michael at amarulasolutions.com>
---
Changes: RFC->v1
	- Add a better commit message
---
 common/fdt_support.c  | 40 ++++++++++++++++++++++++++++++++++++++++
 include/fdt_support.h | 11 +++++++++++
 2 files changed, 51 insertions(+)

Hi Michael,

On Mon, 24 Feb 2020 at 22:10, Michael Trimarchi
<michael at amarulasolutions.com> wrote:
>
> The intent is to reserve memory _and_ prevent it from being included
> in the kernel's linear map. For thos reason it is also necessary to include the
> 'no-map' property for this reserved-mem node.
>
> From Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt:
>
> no-map (optional) - empty property
>     - Indicates the operating system must not create a virtual mapping
>       of the region as part of its standard mapping of system memory,
>       nor permit speculative access to it under any circumstances other
>       than under the control of the device driver using the region.
>
> Signed-off-by: Michael Trimarchi <michael at amarulasolutions.com>
> ---
> Changes: RFC->v1
>         - Add a better commit message
> ---
>  common/fdt_support.c  | 40 ++++++++++++++++++++++++++++++++++++++++
>  include/fdt_support.h | 11 +++++++++++
>  2 files changed, 51 insertions(+)
>
> diff --git a/common/fdt_support.c b/common/fdt_support.c
> index 02cf5c6241..a3662f4358 100644
> --- a/common/fdt_support.c
> +++ b/common/fdt_support.c
> @@ -410,6 +410,46 @@ static int fdt_pack_reg(const void *fdt, void *buf, u64 *address, u64 *size,
>         return p - (char *)buf;
>  }
>
> +int fdt_fixup_reserved_memory(void *blob, const char *area, u64 start[], u64 size[])
> +{
> +       int offs, len;
> +       const char *subpath;
> +       const char *path = "/reserved-memory";
> +       fdt32_t address_cells = cpu_to_fdt32(fdt_address_cells(blob, 0));
> +       fdt32_t size_cells = cpu_to_fdt32(fdt_size_cells(blob, 0));
> +       u8 temp[16]; /* Up to 64-bit address + 64-bit size */
> +
> +       offs = fdt_path_offset(blob, path);
> +       if (offs < 0) {
> +               debug("Node %s not found\n", path);
> +               path = "/";
> +               subpath = "reserved-memory";
> +               offs = fdt_path_offset(blob, path);

Error check

> +               offs = fdt_add_subnode(blob, offs, subpath);
> +               if (offs < 0) {
> +                       printf("Could not create %s%s node.\n", path, subpath);
> +                       return -1;
> +               }
> +               path = "/reserved-memory";
> +               offs = fdt_path_offset(blob, path);
> +
> +               fdt_setprop(blob, offs, "#address-cells", &address_cells, sizeof(address_cells));
> +               fdt_setprop(blob, offs, "#size-cells", &size_cells, sizeof(size_cells));
> +               fdt_setprop(blob, offs, "ranges", NULL, 0);

Need error-checking on these three

> +       }
> +
> +       offs = fdt_add_subnode(blob, offs, area ? : "private");

Is this in a binding file somewhere?

> +       if (offs < 0) {
> +               printf("Could not create %s%s node.\n", path, subpath);
> +               return -1;

return offs

> +       }
> +
> +       fdt_setprop(blob, offs, "no-map", NULL, 0);

and this?

Also needs error check

> +       len = fdt_pack_reg(blob, temp, start, size, 1);
> +       fdt_setprop(blob, offs, "reg", temp, len);

blank line before return

> +       return 0;
> +}
> +
>  #if CONFIG_NR_DRAM_BANKS > 4
>  #define MEMORY_BANKS_MAX CONFIG_NR_DRAM_BANKS
>  #else
> diff --git a/include/fdt_support.h b/include/fdt_support.h
> index ba14acd7f6..7c8a280f53 100644
> --- a/include/fdt_support.h
> +++ b/include/fdt_support.h
> @@ -93,6 +93,17 @@ void do_fixup_by_compat_u32(void *fdt, const char *compat,
>   */
>  int fdt_fixup_memory(void *blob, u64 start, u64 size);
>
> +/**
> + * Setup the memory reserved node in the DT. Creates one if none was existing before.
> + *
> + * @param blob         FDT blob to update
> + * @param area         Reserved area name
> + * @param start                Begin of DRAM mapping in physical memory
> + * @param size         Size of the single memory bank
> + * @return 0 if ok, or -1 or -FDT_ERR_... on error

Really we should return an FDT_ERR always. -1 is not a good idea and
in fact is an FDT_ERR

> + */
> +int fdt_fixup_reserved_memory(void *blob, const char *area, u64 start[], u64 size[]);
> +
>  /**
>   * Fill the DT memory node with multiple memory banks.
>   * Creates the node if none was existing before.
> --
> 2.17.1
>

Regards,
Simon

Hi

On Wed, Feb 26, 2020 at 4:33 PM Simon Glass <sjg at chromium.org> wrote:
>
> Hi Michael,
>
> On Mon, 24 Feb 2020 at 22:10, Michael Trimarchi
> <michael at amarulasolutions.com> wrote:
> >
> > The intent is to reserve memory _and_ prevent it from being included
> > in the kernel's linear map. For thos reason it is also necessary to include the
> > 'no-map' property for this reserved-mem node.
> >
> > From Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt:
> >
> > no-map (optional) - empty property
> >     - Indicates the operating system must not create a virtual mapping
> >       of the region as part of its standard mapping of system memory,
> >       nor permit speculative access to it under any circumstances other
> >       than under the control of the device driver using the region.
> >
> > Signed-off-by: Michael Trimarchi <michael at amarulasolutions.com>
> > ---
> > Changes: RFC->v1
> >         - Add a better commit message
> > ---
> >  common/fdt_support.c  | 40 ++++++++++++++++++++++++++++++++++++++++
> >  include/fdt_support.h | 11 +++++++++++
> >  2 files changed, 51 insertions(+)
> >
> > diff --git a/common/fdt_support.c b/common/fdt_support.c
> > index 02cf5c6241..a3662f4358 100644
> > --- a/common/fdt_support.c
> > +++ b/common/fdt_support.c
> > @@ -410,6 +410,46 @@ static int fdt_pack_reg(const void *fdt, void *buf, u64 *address, u64 *size,
> >         return p - (char *)buf;
> >  }
> >
> > +int fdt_fixup_reserved_memory(void *blob, const char *area, u64 start[], u64 size[])
> > +{
> > +       int offs, len;
> > +       const char *subpath;
> > +       const char *path = "/reserved-memory";
> > +       fdt32_t address_cells = cpu_to_fdt32(fdt_address_cells(blob, 0));
> > +       fdt32_t size_cells = cpu_to_fdt32(fdt_size_cells(blob, 0));
> > +       u8 temp[16]; /* Up to 64-bit address + 64-bit size */
> > +
> > +       offs = fdt_path_offset(blob, path);
> > +       if (offs < 0) {
> > +               debug("Node %s not found\n", path);
> > +               path = "/";
> > +               subpath = "reserved-memory";
> > +               offs = fdt_path_offset(blob, path);
>
> Error check
>

Ok

> > +               offs = fdt_add_subnode(blob, offs, subpath);
> > +               if (offs < 0) {
> > +                       printf("Could not create %s%s node.\n", path, subpath);
> > +                       return -1;
> > +               }
> > +               path = "/reserved-memory";
> > +               offs = fdt_path_offset(blob, path);
> > +
> > +               fdt_setprop(blob, offs, "#address-cells", &address_cells, sizeof(address_cells));
> > +               fdt_setprop(blob, offs, "#size-cells", &size_cells, sizeof(size_cells));
> > +               fdt_setprop(blob, offs, "ranges", NULL, 0);
>
> Need error-checking on these three
>

ok

> > +       }
> > +
> > +       offs = fdt_add_subnode(blob, offs, area ? : "private");
>
> Is this in a binding file somewhere?
>

The reserved memory is needed to avoid the linux kernel to use it and
to get a persistent framebuffer. On some SoC I have implemented the
reuse on the memory on their graphics driver. I need to check how this
is
documented in Linux. The name of the reserved memory it's not mandatory.

> > +       if (offs < 0) {
> > +               printf("Could not create %s%s node.\n", path, subpath);
> > +               return -1;
>
> return offs
>

ok

> > +       }
> > +
> > +       fdt_setprop(blob, offs, "no-map", NULL, 0);
>
> and this?
>
ok

> Also needs error check
>
> > +       len = fdt_pack_reg(blob, temp, start, size, 1);
> > +       fdt_setprop(blob, offs, "reg", temp, len);
>
> blank line before return
>

done

> > +       return 0;
> > +}
> > +
> >  #if CONFIG_NR_DRAM_BANKS > 4
> >  #define MEMORY_BANKS_MAX CONFIG_NR_DRAM_BANKS
> >  #else
> > diff --git a/include/fdt_support.h b/include/fdt_support.h
> > index ba14acd7f6..7c8a280f53 100644
> > --- a/include/fdt_support.h
> > +++ b/include/fdt_support.h
> > @@ -93,6 +93,17 @@ void do_fixup_by_compat_u32(void *fdt, const char *compat,
> >   */
> >  int fdt_fixup_memory(void *blob, u64 start, u64 size);
> >
> > +/**
> > + * Setup the memory reserved node in the DT. Creates one if none was existing before.
> > + *
> > + * @param blob         FDT blob to update
> > + * @param area         Reserved area name
> > + * @param start                Begin of DRAM mapping in physical memory
> > + * @param size         Size of the single memory bank
> > + * @return 0 if ok, or -1 or -FDT_ERR_... on error
>
> Really we should return an FDT_ERR always. -1 is not a good idea and
> in fact is an FDT_ERR
>

Now with the change FDT_ERR only is returned.

> > + */
> > +int fdt_fixup_reserved_memory(void *blob, const char *area, u64 start[], u64 size[]);
> > +
> >  /**
> >   * Fill the DT memory node with multiple memory banks.
> >   * Creates the node if none was existing before.
> > --
> > 2.17.1
> >
>
> Regards,
> Simon

I will post a new one

Michael

HI Tommaso,

Thank you to have time on this

Michael

On Tue, Feb 25, 2020 at 6:10 AM Michael Trimarchi
<michael@amarulasolutions.com> wrote:
>
> The intent is to reserve memory _and_ prevent it from being included
> in the kernel's linear map. For thos reason it is also necessary to include the
> 'no-map' property for this reserved-mem node.
>
> From Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt:
>
> no-map (optional) - empty property
>     - Indicates the operating system must not create a virtual mapping
>       of the region as part of its standard mapping of system memory,
>       nor permit speculative access to it under any circumstances other
>       than under the control of the device driver using the region.
>
> Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
> ---
> Changes: RFC->v1
>         - Add a better commit message
> ---
>  common/fdt_support.c  | 40 ++++++++++++++++++++++++++++++++++++++++
>  include/fdt_support.h | 11 +++++++++++
>  2 files changed, 51 insertions(+)
>
> diff --git a/common/fdt_support.c b/common/fdt_support.c
> index 02cf5c6241..a3662f4358 100644
> --- a/common/fdt_support.c
> +++ b/common/fdt_support.c
> @@ -410,6 +410,46 @@ static int fdt_pack_reg(const void *fdt, void *buf, u64 *address, u64 *size,
>         return p - (char *)buf;
>  }
>
> +int fdt_fixup_reserved_memory(void *blob, const char *area, u64 start[], u64 size[])
> +{
> +       int offs, len;
> +       const char *subpath;
> +       const char *path = "/reserved-memory";
> +       fdt32_t address_cells = cpu_to_fdt32(fdt_address_cells(blob, 0));
> +       fdt32_t size_cells = cpu_to_fdt32(fdt_size_cells(blob, 0));
> +       u8 temp[16]; /* Up to 64-bit address + 64-bit size */
> +
> +       offs = fdt_path_offset(blob, path);
> +       if (offs < 0) {
> +               debug("Node %s not found\n", path);
> +               path = "/";
> +               subpath = "reserved-memory";
> +               offs = fdt_path_offset(blob, path);
> +               offs = fdt_add_subnode(blob, offs, subpath);
> +               if (offs < 0) {
> +                       printf("Could not create %s%s node.\n", path, subpath);
> +                       return -1;
> +               }
> +               path = "/reserved-memory";
> +               offs = fdt_path_offset(blob, path);
> +
> +               fdt_setprop(blob, offs, "#address-cells", &address_cells, sizeof(address_cells));
> +               fdt_setprop(blob, offs, "#size-cells", &size_cells, sizeof(size_cells));
> +               fdt_setprop(blob, offs, "ranges", NULL, 0);
> +       }
> +
> +       offs = fdt_add_subnode(blob, offs, area ? : "private");
> +       if (offs < 0) {
> +               printf("Could not create %s%s node.\n", path, subpath);
> +               return -1;
> +       }
> +
> +       fdt_setprop(blob, offs, "no-map", NULL, 0);
> +       len = fdt_pack_reg(blob, temp, start, size, 1);
> +       fdt_setprop(blob, offs, "reg", temp, len);
> +       return 0;
> +}
> +
>  #if CONFIG_NR_DRAM_BANKS > 4
>  #define MEMORY_BANKS_MAX CONFIG_NR_DRAM_BANKS
>  #else
> diff --git a/include/fdt_support.h b/include/fdt_support.h
> index ba14acd7f6..7c8a280f53 100644
> --- a/include/fdt_support.h
> +++ b/include/fdt_support.h
> @@ -93,6 +93,17 @@ void do_fixup_by_compat_u32(void *fdt, const char *compat,
>   */
>  int fdt_fixup_memory(void *blob, u64 start, u64 size);
>
> +/**
> + * Setup the memory reserved node in the DT. Creates one if none was existing before.
> + *
> + * @param blob         FDT blob to update
> + * @param area         Reserved area name
> + * @param start                Begin of DRAM mapping in physical memory
> + * @param size         Size of the single memory bank
> + * @return 0 if ok, or -1 or -FDT_ERR_... on error
> + */
> +int fdt_fixup_reserved_memory(void *blob, const char *area, u64 start[], u64 size[]);
> +
>  /**
>   * Fill the DT memory node with multiple memory banks.
>   * Creates the node if none was existing before.
> --
> 2.17.1
>