Re: [PATCH 7/8] drm/loongson: Support to infer DC reversion from CPU's PRID value

[Sui Jingfeng]

Hi,

On 2023/10/30 07:19, Dmitry Baryshkov wrote:
> On Sun, 29 Oct 2023 at 21:46, Sui Jingfeng <suijingfeng@xxxxxxxxxxx> wrote:
> > Due to the fact that the same display IP core has been integrated into
> > different platform, there is a need to differentiate them on the runtime.
> > The DC in LS7A1000/LS2K1000 has the PCI vendor & device ID of 0x0014:0x7A06
> > The DC in LS7A2000/LS2K2000 has the PCI vendor & device ID of 0x0014:0x7A36
> >
> > Because the output ports and host platform of the DC IP varies, without a
> > revision information we can't achieve fine-grained controls. The canonical
> > approach to do such a thing is to read reversion register from the PCIe
> > device. But LS2K1000 SoC was taped out at 2017, it is rather old. Our BIOS
> > engineer don't assign a different revision ID to it, probably because of
> > ignorance.
> >
> > LS2K2000 SoC was newly taped on 2023, we strictly force the BIOS engineer
> > assign a different revision ID(0x10) to it. But the problem is that it is
> > too casual, there is no formal convention or public documented rule
> > established. For Loongson LS2K series SoC, the display controller IP is
> > taped togather with the CPU core. For Loongson LS7A series bridge chips,
> > the display controller IP is taped togather with the bridge chips itself.
> > Consider the fact the all Loongson CPU has a unique PRID, this patch choose
> > to infer DC reversion from CPU's PRID value.
> >
> >   - LS3A4000/LS3A5000 has 0xC0 as its processor ID.
> >   - LS2K2000 has 0xB0 as its processor ID.
> >   - LS2K2000LA has 0xA0 as its processor ID.
> >
> > The provided approach has no dependency on DT or ACPI, thus is preferfed.
> > Besides, this approach can be used to acquire more addtional HW features.
> > So the provided method has the potential to bring more benifits.
> >
> > Signed-off-by: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/loongson/lsdc_drv.h   |  2 ++
> >   drivers/gpu/drm/loongson/lsdc_probe.c | 35 +++++++++++++++++++++++++++
> >   drivers/gpu/drm/loongson/lsdc_probe.h |  2 ++
> >   3 files changed, 39 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/loongson/lsdc_drv.h b/drivers/gpu/drm/loongson/lsdc_drv.h
> > index 46ba9b88a30d..e1f4a2db2a0a 100644
> > --- a/drivers/gpu/drm/loongson/lsdc_drv.h
> > +++ b/drivers/gpu/drm/loongson/lsdc_drv.h
> > @@ -42,6 +42,8 @@
> >   enum loongson_chip_id {
> >          CHIP_LS7A1000 = 0,
> >          CHIP_LS7A2000 = 1,
> > +       CHIP_LS2K1000 = 2,
> > +       CHIP_LS2K2000 = 3,
> >          CHIP_LS_LAST,
> >   };
> >
> > diff --git a/drivers/gpu/drm/loongson/lsdc_probe.c b/drivers/gpu/drm/loongson/lsdc_probe.c
> > index 48ba69bb8a98..f49b642d8f65 100644
> > --- a/drivers/gpu/drm/loongson/lsdc_probe.c
> > +++ b/drivers/gpu/drm/loongson/lsdc_probe.c
> > @@ -54,3 +54,38 @@ unsigned int loongson_cpu_get_prid(u8 *imp, u8 *rev)
> >
> >          return prid;
> >   }
> > +
> > +enum loongson_chip_id loongson_chip_id_fixup(enum loongson_chip_id chip_id)
> > +{
> > +       u8 impl;
> > +
> > +       if (loongson_cpu_get_prid(&impl, NULL)) {
> > +               /*
> > +                * LS2K2000 only has the LoongArch edition.
> > +                */
> > +               if (chip_id == CHIP_LS7A2000) {
> > +                       if (impl == LOONGARCH_CPU_IMP_LS2K2000)
> > +                               return CHIP_LS2K2000;
> > +               }
> > +
> > +               /*
> > +                * LS2K1000 has the LoongArch edition(with two LA264 CPU core)
> > +                * and the Mips edition(with two mips64r2 CPU core), Only the
> > +                * instruction set of the CPU are changed, the peripheral
> > +                * devices are basically same.
> > +                */
> > +               if (chip_id == CHIP_LS7A1000) {
> > +#if defined(__loongarch__)
> > +                       if (impl == LOONGARCH_CPU_IMP_LS2K1000)
> > +                               return CHIP_LS2K1000;
> > +#endif
> > +
> > +#if defined(__mips__)
> > +                       if (impl == LOONGSON_CPU_MIPS_IMP_LS2K)
> > +                               return CHIP_LS2K1000;
> > +#endif
> Can you drop the ifdefs here? The code blocks do not seem to conflict
> with each other.

OK, no problem. Will be fixed at the next version.

> > +               }
> > +       }
> > +
> > +       return chip_id;
> > +}
> > diff --git a/drivers/gpu/drm/loongson/lsdc_probe.h b/drivers/gpu/drm/loongson/lsdc_probe.h
> > index 8bb6de2e3c64..8c630c5c90ce 100644
> > --- a/drivers/gpu/drm/loongson/lsdc_probe.h
> > +++ b/drivers/gpu/drm/loongson/lsdc_probe.h
> > @@ -9,4 +9,6 @@
> >   /* Helpers for chip detection */
> >   unsigned int loongson_cpu_get_prid(u8 *impl, u8 *rev);
> >
> > +enum loongson_chip_id loongson_chip_id_fixup(enum loongson_chip_id chip_id);
> > +
> >   #endif
> > --
> > 2.34.1