Re: [PATCH 1/7] irqchip/gic-v3: Add a DMA Non-Coherent flag

[Marc Zyngier]

On Tue, 14 Mar 2023 13:25:28 +0000,
Lucas Tanure <lucas.tanure@xxxxxxxxxxxxx> wrote:
> 
> On 10-03-2023 12:04, Robin Murphy wrote:
> > On 2023-03-10 11:41, Peter Geis wrote:
> >> On Fri, Mar 10, 2023 at 3:05 AM Lucas Tanure
> >> <lucas.tanure@xxxxxxxxxxxxx> wrote:
> >>> 
> >>> The GIC600 integration in RK356x, used in rk3588, doesn't support
> >>> any of the shareability or cacheability attributes, and requires
> >>> both values to be set to 0b00 for all the ITS and Redistributor
> >>> tables.
> >>> 
> >>> This is loosely based on prior work from XiaoDong Huang and
> >>> Peter Geis fixing this issue specifically for Rockchip 356x.
> >> 
> >> Good Morning,
> >> 
> >> Since the gic is using dma, would it be reasonable to have all memory
> >> allocations be requested with the GFP_DMA flag? Otherwise this doesn't
> >> fully solve the problem for rk356x, where only the lower 4GB range is
> >> DMA capable, but this tends to get allocated in the upper 4GB on 8GB
> >> boards.
> > 
> > Not really, because there's no fixed definition of what GFP_DMA
> > actually means, and it may mean nothing (same for GFP_DMA32, which
> > may or may not be meaningful depending on kernel config and platform
> > topology). Drivers should really use the DMA API allocation
> > functions if they care about what they get, which comes back round
> > to the notion from years ago of converting the ITS driver to a
> > regular platform driver, so it can benefit from regular DT concepts
> > like "dma-ranges" automatically.
> > 
> > Thanks,
> > Robin.
> > 
> I am looking how to do that conversion to platform driver.
> But about the communication between irq-gic-v3-its and irq-gic-v3.
> Should irq-gic-v3-its be a MFD child of irq-gic-v3?

MFD? I'd rather suggest an VME bus driver. ;-)

Seriously, this is an interrupt controller. Nothing else. It should
probe the parent irqdomain, and stack onto that. No parent? Probe
deferral.

> Or use the component bind/unbind framework?

I don't understand what you mean here.

	M.

-- 
Without deviation from the norm, progress is not possible.