Re: [PATCH v2] drm/amdgpu: add dce6 drm_panic support

[Jocelyn Falempe]

On 25/09/2024 10:33, Jocelyn Falempe wrote:
> On 24/09/2024 16:02, Alex Deucher wrote:
> > On Fri, Sep 20, 2024 at 11:36 AM Jocelyn Falempe <jfalempe@xxxxxxxxxx> 
> > wrote:
> > > On 17/09/2024 15:21, Alex Deucher wrote:
> > > > On Mon, Aug 12, 2024 at 2:10 AM Lu Yao <yaolu@xxxxxxxxxx> wrote:
> > > > > Add support for the drm_panic module, which displays a pretty user
> > > > > friendly message on the screen when a Linux kernel panic occurs.
> > > > >
> > > > > Signed-off-by: Lu Yao <yaolu@xxxxxxxxxx>
> > > >
> > > > Patch looks good to me.  Any chance you want to convert the other
> > > > non-DC dce files (dce_v8_0.c, dce_v10_0.c, dce_v11_0.c) while you are
> > > > at it?
> > >
> > > I've made a similar patch in amdgpu_dm_plane.c, and it works on a Radeon
> > > pro w6400.
> > > But it only works when I'm in a VT terminal (so the framebuffer is
> > > linear and CPU accessible).
> > > When under Gnome/Wayland, the flag AMDGPU_GEM_CREATE_NO_CPU_ACCESS is
> > > set, so that means I can't vmap it ?
> >
> > It just means that the application does not need CPU access.  Whether
> > or not the CPU can access the buffer or not depends on the size of the
> > PCI BAR.  E.g., if the driver or bios has resized the PCI BAR, then
> > the CPU can access the entire BAR, but if not you are generally
> > limited to the first 256M of framebuffer.
>
> I tried to use ttm_bo_kmap() anyway, it returns a valid virtual address, 
> but writing to it has no effect on the display.
> > > Also I don't know if there is a similar way to disable
> > > tiling/compression on this hardware.
> >
> > UNP_GRPH_CONTROL on chips with DCE display hardware and
> > DCSURF_ADDR_CONFIG and DCSURF_TILING_CONFIG on DCN display hardware.

I've now a working Prototype on a Radeon pro W6400.

Here is what I do to disable tiling:

REG_UPDATE(DCHUBP_REQ_SIZE_CONFIG, SWATH_HEIGHT, 0);
REG_UPDATE(DCSURF_TILING_CONFIG, SW_MODE, DC_SW_LINEAR);

REG_UPDATE_6(DCSURF_SURFACE_CONTROL,
		PRIMARY_SURFACE_DCC_EN, 0,
		PRIMARY_SURFACE_DCC_IND_BLK, 0,
		PRIMARY_SURFACE_DCC_IND_BLK_C, 0,
		SECONDARY_SURFACE_DCC_EN, 0,
		SECONDARY_SURFACE_DCC_IND_BLK, 0,
		SECONDARY_SURFACE_DCC_IND_BLK_C, 0);

I also need to call this, to refresh the display:

hubp->funcs->hubp_program_surface_flip_and_addr(hubp, 
&dc_plane_state->address, dc_plane_state->flip_immediate);

And I use a modified version of amdgpu_ttm_access_memory() to write to 
the framebuffer.

I will send a patch when I've time to make a clean version.

Best regards,

--

Jocelyn