[PATCH v4 05/27] lmb: make LMB memory map persistent and global

[Sughosh Ganu]

On Tue, 29 Oct 2024 at 09:19, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
>
> On Tue, 29 Oct 2024 at 02:50, Janne Grunau <janne at jannau.net> wrote:
> >
> > On Mon, Aug 26, 2024 at 05:29:18PM +0530, Sughosh Ganu wrote:
> > > The current LMB API's for allocating and reserving memory use a
> > > per-caller based memory view. Memory allocated by a caller can then be
> > > overwritten by another caller. Make these allocations and reservations
> > > persistent using the alloced list data structure.
> > >
> > > Two alloced lists are declared -- one for the available(free) memory,
> > > and one for the used memory. Once full, the list can then be extended
> > > at runtime.
> > >
> > > Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> > > Signed-off-by: Simon Glass <sjg at chromium.org>
> > > [sjg: Optimise the logic to add a region in lmb_add_region_flags()]
> > > [sjg: Use a stack to store pointer of lmb struct when running lmb tests]
> > > ---
> > > Changes since V3:
> > > * Fix checkpatch warnings of spaces between function name and
> > >   open parantheses.
> > > * s/uint64_t/u64 as suggested by checkpatch.
> > > * Remove unneccessary parantheses in lmb.c as suggested by checkpatch.
> > > * Fix alignment in test/cmd/bdinfo.c as suggested by checkpatch.
> >
> > [...]
> >
> > >  drivers/iommu/apple_dart.c           |   8 +-
> >
> > [...]
> >
> > > diff --git a/drivers/iommu/apple_dart.c b/drivers/iommu/apple_dart.c
> > > index 9327dea1e3..611ac7cd6d 100644
> > > --- a/drivers/iommu/apple_dart.c
> > > +++ b/drivers/iommu/apple_dart.c
> > > @@ -70,7 +70,6 @@
> > >
> > >  struct apple_dart_priv {
> > >       void *base;
> > > -     struct lmb lmb;
> > >       u64 *l1, *l2;
> > >       int bypass, shift;
> > >
> > > @@ -124,7 +123,7 @@ static dma_addr_t apple_dart_map(struct udevice *dev, void *addr, size_t size)
> > >       off = (phys_addr_t)addr - paddr;
> > >       psize = ALIGN(size + off, DART_PAGE_SIZE);
> > >
> > > -     dva = lmb_alloc(&priv->lmb, psize, DART_PAGE_SIZE);
> > > +     dva = lmb_alloc(psize, DART_PAGE_SIZE);
> > >
> > >       idx = dva / DART_PAGE_SIZE;
> > >       for (i = 0; i < psize / DART_PAGE_SIZE; i++) {
> > > @@ -160,7 +159,7 @@ static void apple_dart_unmap(struct udevice *dev, dma_addr_t addr, size_t size)
> > >                          (unsigned long)&priv->l2[idx + i]);
> > >       priv->flush_tlb(priv);
> > >
> > > -     lmb_free(&priv->lmb, dva, psize);
> > > +     lmb_free(dva, psize);
> > >  }
> > >
> > >  static struct iommu_ops apple_dart_ops = {
> > > @@ -213,8 +212,7 @@ static int apple_dart_probe(struct udevice *dev)
> > >       priv->dvabase = DART_PAGE_SIZE;
> > >       priv->dvaend = SZ_4G - DART_PAGE_SIZE;
> > >
> > > -     lmb_init(&priv->lmb);
> > > -     lmb_add(&priv->lmb, priv->dvabase, priv->dvaend - priv->dvabase);
> > > +     lmb_add(priv->dvabase, priv->dvaend - priv->dvabase);
> >
> > no. This breaks everything. apple_dart is an iommu and used struct lmb
> > to manage the IO virtual address space. This has nothing to do
> > with system memory.
> > Depending on the allocation strategy this will cause all sorts of
> > problems since the IO and the physical memory address space does not
> > overlap on apple silicon devices. IOVA is for many devices only 32-bit
> > but physical memory starts at 0x10_0000_0000 or 0x100_0000_0000.
> > Every device has its own iommu / IOVA space so sharing the space between
> > all of them is another problem. I'd assume only theoretical due to the
> > limited driver support and memory use in u-boot.
> >
> > My current plan to fix this is to resurrect the old lmb code under a
> > different name.
>
> Firstly, apologies for breaking the driver. Looking at the code, it
> looks like the driver works with a dva address range in the first 4GB.
> I think what the driver expects is fairly straightforward, with a
> top-down allocation scheme. I have sent a patch [1] which replaces the
> LMB calls with a call to the allocation function. Can you please check
> if this works on the board? Looking at how the driver is obtaining the
> dva addresses, I think this logic should suffice. Thanks.
>
> -sughosh
>
> [1] - https://patchwork.ozlabs.org/project/uboot/patch/20241029033915.423211-1-sughosh.ganu@linaro.org/

This would not work as it does not consider freeing of the va
addresses. So there might be a need for a parallel lmb instance for
this.

-sughosh

>
>
> -sughosh
>
> >
> > Not sure about the same change in sandbox_iommu but I guess it could be
> > ok as there is no sandbox.
> >
> > Janne