Subject: RE: [PATCH v4 07/25] ocxl: Add functions to map/unmap LPC memory

From: "Alastair D'Silva" <[email-masked]>
Date: Fri, 3 Apr 2020 14:50:36 +1100

> -----Original Message-----
> From: Dan Williams <[email-masked]>
> Sent: Wednesday, 1 April 2020 7:49 PM
> To: Alastair D'Silva <[email-masked]>
> Cc: Aneesh Kumar K . V <[email-masked]>; Oliver O'Halloran
> <[email-masked]>; Benjamin Herrenschmidt
> <[email-masked]>; Paul Mackerras <[email-masked]>; Michael
> Ellerman <[email-masked]>; Frederic Barrat <[email-masked]>;
> Andrew Donnellan <[email-masked]>; Arnd Bergmann
> <[email-masked]>; Greg Kroah-Hartman <[email-masked]>;
> Vishal Verma <[email-masked]>; Dave Jiang
> <[email-masked]>; Ira Weiny <[email-masked]>; Andrew Morton
> <[email-masked]>; Mauro Carvalho Chehab
> <[email-masked]>; David S. Miller <[email-masked]>;
> Rob Herring <[email-masked]>; Anton Blanchard <[email-masked]>;
> Krzysztof Kozlowski <[email-masked]>; Mahesh Salgaonkar
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> Kurz <[email-masked]>; Nicholas Piggin <[email-masked]>; Masahiro
> Yamada <[email-masked]>; Alexey Kardashevskiy
> <[email-masked]>; Linux Kernel Mailing List <[email-masked]>;
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> Subject: Re: [PATCH v4 07/25] ocxl: Add functions to map/unmap LPC
> memory
> 
> On Sun, Mar 29, 2020 at 10:23 PM Alastair D'Silva <[email-masked]>
> wrote:
> >
> > Add functions to map/unmap LPC memory
> >
> 
> "map memory" is an overloaded term. I'm guessing this patch has nothing to
> do with mapping memory in the MMU. Is it updating hardware resource
> decoders to start claiming address space that was allocated previously?
> 

It's similar to MMIO - these calls end up setting up a BAR which places the LPC
memory into a physical memory range addressable by the kernel.

> > Signed-off-by: Alastair D'Silva <[email-masked]>
> > Acked-by: Frederic Barrat <[email-masked]>
> > ---
> >  drivers/misc/ocxl/core.c          | 51 +++++++++++++++++++++++++++++++
> >  drivers/misc/ocxl/ocxl_internal.h |  3 ++
> >  include/misc/ocxl.h               | 21 +++++++++++++
> >  3 files changed, 75 insertions(+)
> >
> > diff --git a/drivers/misc/ocxl/core.c b/drivers/misc/ocxl/core.c index
> > 2531c6cf19a0..75ff14e3882a 100644
> > --- a/drivers/misc/ocxl/core.c
> > +++ b/drivers/misc/ocxl/core.c
> > @@ -210,6 +210,56 @@ static void unmap_mmio_areas(struct ocxl_afu
> *afu)
> >         release_fn_bar(afu->fn, afu->config.global_mmio_bar);  }
> >
> > +int ocxl_afu_map_lpc_mem(struct ocxl_afu *afu) {
> > +       struct pci_dev *dev = to_pci_dev(afu->fn->dev.parent);
> > +
> > +       if ((afu->config.lpc_mem_size + afu-
> >config.special_purpose_mem_size) == 0)
> > +               return 0;
> > +
> > +       afu->lpc_base_addr = ocxl_link_lpc_map(afu->fn->link, dev);
> > +       if (afu->lpc_base_addr == 0)
> > +               return -EINVAL;
> > +
> > +       if (afu->config.lpc_mem_size > 0) {
> > +               afu->lpc_res.start = afu->lpc_base_addr + afu-
> >config.lpc_mem_offset;
> > +               afu->lpc_res.end = afu->lpc_res.start + afu->config.lpc_mem_size
> - 1;
> > +       }
> > +
> > +       if (afu->config.special_purpose_mem_size > 0) {
> > +               afu->special_purpose_res.start = afu->lpc_base_addr +
> > +                                                afu->config.special_purpose_mem_offset;
> > +               afu->special_purpose_res.end = afu->special_purpose_res.start +
> > +                                              afu->config.special_purpose_mem_size - 1;
> > +       }
> > +
> > +       return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(ocxl_afu_map_lpc_mem);
> > +
> > +struct resource *ocxl_afu_lpc_mem(struct ocxl_afu *afu) {
> > +       return &afu->lpc_res;
> > +}
> > +EXPORT_SYMBOL_GPL(ocxl_afu_lpc_mem);
> > +
> > +static void unmap_lpc_mem(struct ocxl_afu *afu) {
> > +       struct pci_dev *dev = to_pci_dev(afu->fn->dev.parent);
> > +
> > +       if (afu->lpc_res.start || afu->special_purpose_res.start) {
> > +               void *link = afu->fn->link;
> > +
> > +               // only release the link when the the last consumer calls release
> > +               ocxl_link_lpc_release(link, dev);
> > +
> > +               afu->lpc_res.start = 0;
> > +               afu->lpc_res.end = 0;
> > +               afu->special_purpose_res.start = 0;
> > +               afu->special_purpose_res.end = 0;
> > +       }
> > +}
> > +
> >  static int configure_afu(struct ocxl_afu *afu, u8 afu_idx, struct
> > pci_dev *dev)  {
> >         int rc;
> > @@ -251,6 +301,7 @@ static int configure_afu(struct ocxl_afu *afu, u8
> > afu_idx, struct pci_dev *dev)
> >
> >  static void deconfigure_afu(struct ocxl_afu *afu)  {
> > +       unmap_lpc_mem(afu);
> >         unmap_mmio_areas(afu);
> >         reclaim_afu_pasid(afu);
> >         reclaim_afu_actag(afu);
> > diff --git a/drivers/misc/ocxl/ocxl_internal.h
> > b/drivers/misc/ocxl/ocxl_internal.h
> > index 2d7575225bd7..7b975a89db7b 100644
> > --- a/drivers/misc/ocxl/ocxl_internal.h
> > +++ b/drivers/misc/ocxl/ocxl_internal.h
> > @@ -52,6 +52,9 @@ struct ocxl_afu {
> >         void __iomem *global_mmio_ptr;
> >         u64 pp_mmio_start;
> >         void *private;
> > +       u64 lpc_base_addr; /* Covers both LPC & special purpose memory */
> > +       struct resource lpc_res;
> > +       struct resource special_purpose_res;
> >  };
> >
> >  enum ocxl_context_status {
> > diff --git a/include/misc/ocxl.h b/include/misc/ocxl.h index
> > 357ef1aadbc0..d8b0b4d46bfb 100644
> > --- a/include/misc/ocxl.h
> > +++ b/include/misc/ocxl.h
> > @@ -203,6 +203,27 @@ int ocxl_irq_set_handler(struct ocxl_context
> > *ctx, int irq_id,
> >
> >  // AFU Metadata
> >
> > +/**
> > + * ocxl_afu_map_lpc_mem() - Map the LPC system & special purpose
> > +memory for an AFU
> > + * Do not call this during device discovery, as there may me multiple
> 
> s/me/be/
> 
> 
> > + * devices on a link, and the memory is mapped for the whole link,
> > +not
> > + * just one device. It should only be called after all devices have
> > + * registered their memory on the link.
> > + *
> > + * @afu: The AFU that has the LPC memory to map
> > + *
> > + * Returns 0 on success, negative on failure  */ int
> > +ocxl_afu_map_lpc_mem(struct ocxl_afu *afu);
> > +
> > +/**
> > + * ocxl_afu_lpc_mem() - Get the physical address range of LPC memory
> > +for an AFU
> > + * @afu: The AFU associated with the LPC memory
> > + *
> > + * Returns a pointer to the resource struct for the physical address
> > +range  */ struct resource *ocxl_afu_lpc_mem(struct ocxl_afu *afu);
> > +
> >  /**
> >   * ocxl_afu_config() - Get a pointer to the config for an AFU
> >   * @afu: a pointer to the AFU to get the config for
> > --
> > 2.24.1
> >

-- 
Alastair D'Silva           mob: 0423 762 819
skype: alastair_dsilva     msn: [email-masked]
blog: http://alastair.d-silva.org    Twitter: @EvilDeece