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From:   Peng Fan <peng.fan@nxp.com>
To:     TingHan Shen <tinghan.shen@mediatek.com>,
        Mathieu Poirier <mathieu.poirier@linaro.org>
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Subject: RE: [PATCH v2 4/9] remoteproc: mediatek: Support probing for the 2nd
 core of dual-core SCP
Thread-Topic: [PATCH v2 4/9] remoteproc: mediatek: Support probing for the 2nd
 core of dual-core SCP
Thread-Index: AQHYu9+KPWXRQoq9AE6UEWxurIDkea3VcYyAgAyedWWAAFgEAIAEObIAgAYdNdA=
Date:   Fri, 23 Sep 2022 07:12:57 +0000
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> Subject: Re: [PATCH v2 4/9] remoteproc: mediatek: Support probing for the
> 2nd core of dual-core SCP
>=20
> On Fri, 2022-09-16 at 11:15 -0600, Mathieu Poirier wrote:
> > On Fri, 16 Sept 2022 at 06:00, TingHan Shen
> <tinghan.shen@mediatek.com> wrote:
> > >
> > > On Thu, 2022-09-08 at 14:58 -0600, Mathieu Poirier wrote:
> > > > On Thu, 8 Sept 2022 at 05:21, Tinghan Shen
> > > > <tinghan.shen@mediatek.com>
> > > > wrote:
> > > >
> > > > > Hi Mathieu,
> > > > >
> > > > > > > The mtk_scp.c driver only supports the single core SCP and
> > > > > > > the 1st core of a dual-core SCP. This patch extends it for th=
e 2nd
> core.
> > > > > > >
> > > > > > > MT8195 SCP is a dual-core MCU. Both cores are housed in the
> > > > > > > same
> > > > >
> > > > > subsys.
> > > > > >
> > > > > > s/subsys/subsystem
> > > > > >
> > > > > > > They have the same viewpoint of registers and memory.
> > > > > > >
> > > > > > > Core 1 of the SCP features its own set of core configuration
> > > > > > > registers, interrupt controller, timers, and DMAs. The rest
> > > > > > > of the peripherals in this subsystem are shared by core 0 and
> core 1.
> > > > > > >
> > > > > > > As for memory, core 1 has its own cache memory. the SCP SRAM
> > > > > > > is shared
> > > > > >
> > > > > > /the/The
> > > > > >
> > > > > > > by core 0 and core 1.
> > > > > > >
> > > > > > > Signed-off-by: Tinghan Shen <tinghan.shen@mediatek.com>
> > > > > > > ---
> > > > > > >  drivers/remoteproc/mtk_scp.c | 22 ++++++++++++++++++++--
> > > > > > >  1 file changed, 20 insertions(+), 2 deletions(-)
> > > > > > >
> > > > > > > diff --git a/drivers/remoteproc/mtk_scp.c
> > > > >
> > > > > b/drivers/remoteproc/mtk_scp.c
> > > > > > > index 3510c6d0bbc8..91b4aefde4ac 100644
> > > > > > > --- a/drivers/remoteproc/mtk_scp.c
> > > > > > > +++ b/drivers/remoteproc/mtk_scp.c
> > > > > > > @@ -23,6 +23,10 @@
> > > > > > >  #define MAX_CODE_SIZE 0x500000  #define
> > > > > > > SECTION_NAME_IPI_BUFFER ".ipi_buffer"
> > > > > > >
> > > > > > > +#define SCP_CORE_0 0
> > > > > > > +#define SCP_CORE_1 1
> > > > > > > +#define SCP_CORE_SINGLE 0xF
> > > > > > > +
> > > > > > >  /**
> > > > > > >   * scp_get() - get a reference to SCP.
> > > > > > >   *
> > > > > > > @@ -836,6 +840,7 @@ static int scp_probe(struct
> platform_device *pdev)
> > > > > > >     struct resource *res;
> > > > > > >     const char *fw_name =3D "scp.img";
> > > > > > >     int ret, i;
> > > > > > > +   u32 core_id =3D SCP_CORE_SINGLE;
> > > > > > >
> > > > > > >     ret =3D rproc_of_parse_firmware(dev, 0, &fw_name);
> > > > > > >     if (ret < 0 && ret !=3D -EINVAL) @@ -851,8 +856,16 @@
> > > > > > > static int scp_probe(struct platform_device *pdev)
> > > > > > >     scp->data =3D of_device_get_match_data(dev);
> > > > > > >     platform_set_drvdata(pdev, scp);
> > > > > > >
> > > > > > > +   ret =3D of_property_read_u32_index(dev->of_node,
> > > > >
> > > > > "mediatek,scp-core", 1, &core_id);
> > > > > > > +   if (ret =3D=3D 0)
> > > > > > > +           dev_info(dev, "Boot SCP dual core %u\n",
> > > > > > > + core_id);
> > > > > >
> > > > > > Why is the DT property "mediatek,scp-core" needed at all?
> > > > > > Since the
> > > > >
> > > > > compatible
> > > > > > "mediatek,mt8195-scp-dual" has already been defined previously
> > > > > > in this
> > > > >
> > > > > patchset,
> > > > > > initialising the second core, if present, is a matter of
> > > > > > looking at the compatile string.
> > > > >
> > > > > This idea of identify cores by the compatible looks workable.
> > > > > I'll update this series at next version.
> > > > > Thanks!
> > > > >
> > > > > >
> > > > > > > +
> > > > > > >     res =3D platform_get_resource_byname(pdev,
> IORESOURCE_MEM, "sram");
> > > > > > > -   scp->sram_base =3D devm_ioremap_resource(dev, res);
> > > > > > > +   if (core_id =3D=3D SCP_CORE_1)
> > > > > > > +           scp->sram_base =3D devm_ioremap(dev, res->start,
> > > > >
> > > > > resource_size(res));
> > > > > > > +   else
> > > > > > > +           scp->sram_base =3D devm_ioremap_resource(dev,
> > > > > > > + res);
> > > > > > > +
> > > > > >
> > > > > > This looks very broken...  For this to work you would need to
> > > > > > have two DT entries with the "mediatek,mt8195-scp-dual"
> > > > > > compatible properly, one with "mediatek,scp-core =3D <&scp_dual=
1
> > > > > > 0>;" and another one with
> > > > >
> > > > > "mediatek,scp-core =3D <&scp_dual0 1>;".
> > > > > >
> > > > > > Which is also very broken...  Here you have a binding whose
> > > > > > first
> > > > >
> > > > > argument is a
> > > > > > reference to the core sibling while the second argument is a
> > > > >
> > > > > characteristic of
> > > > > > the current core, which is highly confusing.
> > > > > >
> > > > > > I suggest what when you see the compatible binding
> > > > >
> > > > > "mediatek,mt8195-scp", a
> > > > > > single core is initialized.  If you see
> > > > > > "mediatek,mt8195-scp-dual", both
> > > > >
> > > > > cores
> > > > > > are initialized as part of the _same_ probe.
> > > > > >
> > > > > > If the above analysis is not correct it means I misinterpreted
> > > > > > your work and if so, a serious amount of comments is needed
> > > > > > _and_ a very
> > > > >
> > > > > detailed
> > > > > > example in "mtk,scp.yaml" that leaves no room for interpretatio=
n.
> > > > > >
> > > > > > I will stop reviewing this patchset until you have clarified
> > > > > > how this
> > > > >
> > > > > works.
> > > > > >
> > > > > > Thanks,
> > > > > > Mathieu
> > > > >
> > > > > There's one problem of initializng the CORE1 using the same probe
> flow.
> > > > > The register space of CORE0 and CORE1 are overlapped in the devic=
e
> node.
> > > > > Both cores need to use the 'cfg' registers defined in scp yaml.
> > > > > The devm_ioremap_resource catches address overlapping and
> > > > > returns error when probing CORE1 driver.
> > > > >
> > > >
> > > > That is exactly why I suggest to initialise both cores within the s=
ame
> > > > probe() function.
> > > >
> > >
> > > Hi Mathieu,
> > >
> > > I'm thinking about how to initialise in the same probe() function.
> > > I'm wondering if this implies that using one scp driver to initialize=
 2 cores?
> > > If it is, I assume the dts descriptions for both cores should be cont=
ained
> in one node.
> > >
> > > When there's one node for both cores, it looks like that there is a
> problem of
> > > using dma_allocate_coherent(). Each core has its own reserved memory
> region.
> > > When there's only one device for both cores, it's not able to identif=
y the
> memory region
> > > by the device parameter of dma_allocate_coherent().
> > >
> > > Is it acceptable to consider manually allocating core 1 device in the
> probe() when probing core 0?
> >
> > Look at what Suman did for TI's K3 R5[1] and DSP[2] platforms.
> > Reviewing the bindings for both platforms will also give you a good
> > idea of how things work.
> >
> > [1].
> https://eur01.safelinks.protection.outlook.com/?url=3Dhttps%3A%2F%2Furlde
> fense.com%2Fv3%2F__https%3A%2F%2Felixir.bootlin.com%2Flinux%2Fv6.0-
> rc5%2Fsource%2Fdrivers%2Fremoteproc%2Fti_k3_r5_remoteproc.c*L1683_
> _%3BIw!!CTRNKA9wMg0ARbw!zVcjdLSfKYGO5YQMNGqq339mle8u0VdULX3
> 0z0XV4vo3vCb9Wy-
> w5ixOTmzbv1akubM%24&amp;data=3D05%7C01%7Cpeng.fan%40nxp.com%7
> C2cf76b2f15544cf3d06308da9a23f00a%7C686ea1d3bc2b4c6fa92cd99c5c301
> 635%7C0%7C0%7C637991776400238974%7CUnknown%7CTWFpbGZsb3d8e
> yJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D
> %7C3000%7C%7C%7C&amp;sdata=3Ddz0FlQQmKI4C67XCX%2BZ6%2Bin%2Btq
> 2DEWLb5YA%2FxGLOxHc%3D&amp;reserved=3D0
> > [2].
> https://eur01.safelinks.protection.outlook.com/?url=3Dhttps%3A%2F%2Furlde
> fense.com%2Fv3%2F__https%3A%2F%2Felixir.bootlin.com%2Flinux%2Fv6.0-
> rc5%2Fsource%2Fdrivers%2Fremoteproc%2Fti_k3_dsp_remoteproc.c*L673_
> _%3BIw!!CTRNKA9wMg0ARbw!zVcjdLSfKYGO5YQMNGqq339mle8u0VdULX3
> 0z0XV4vo3vCb9Wy-
> w5ixOTmzbfE2dtBg%24&amp;data=3D05%7C01%7Cpeng.fan%40nxp.com%7C
> 2cf76b2f15544cf3d06308da9a23f00a%7C686ea1d3bc2b4c6fa92cd99c5c3016
> 35%7C0%7C0%7C637991776400238974%7CUnknown%7CTWFpbGZsb3d8ey
> JWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D
> %7C3000%7C%7C%7C&amp;sdata=3DYn7MOo2uoDOVRW47O1yq8W3c%2BYg
> G5URr7RdLKsmpLrk%3D&amp;reserved=3D0
> >
>=20
> Hi Mathieu,
>=20
> My plan is changing the dts as following,
>=20
> scp core 0 {
> 	// Keep current properties untouched.
> 	compatible =3D "mediatek,mt8195-scp";
>=20
> 	// core 0 properties...
>=20
> 	// Add a new property for multi-core scp.
> 	// if not present, it's single core.
> 	// if present and core id =3D 0, it's the main core, otherwise the sub
> cores.
> 	mediatek,scp-core =3D <0>;
>=20
> 	// add sub cores as sub node.
> 	// sub nodes can find parent by OF API.
> 	scp core 1 {
> 		// use the same compatile name as core 0.
> 		compatible =3D "mediatek,mt8195-scp";
>=20
> 		// assign id > 0 to sub cores.
> 		mediatek,scp-core =3D <1>;
>=20
> 		// core 1 properties...
> 	};
> };

Not know the HW arch, but this looks a bit weird, scp core 1 is
a sub node of scp core 0.

>=20
>=20
> The driver probe/remove behavior will be modified as below,
>=20
> scp probe() {
> 	// common init...
>=20
> 	// check core id to have different memory mapping flow
> 	if (core id =3D=3D 0)
> 		// mapping cfg, sram and others
> 	else
> 		// mapping sram
> 		// reuse the cfg paddr/vaddr from core 0

Oh, I understand why you need ioremap_resource, so core0/1 share
same register address space?

Regards,
Peng.
>=20
> 	// common init...
>=20
> 	if (core id =3D=3D 0) {
> 		ret =3D of_platform_populate(...)
>=20
> 		// boot core 0 and sub cores
> 		rproc_add();
> 	} else {
> 		// add sub core as sub device to main core
> 		rproc_add_subdev()
>=20
> 		rproc->auto_boot =3D false;
> 		rpoc_add();
> 	}
> }
>=20
> scp_remove() {
>=20
> 	if (core id =3D=3D 0)
> 		of_platform_depopulate()
> 	else
> 		rproc_remove_subdev()
>=20
> 	// remove core
> }
>=20
>=20
>=20
> Best regards,
> TingHan
>=20
>=20
>=20