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Subject: Re: [PATCH v3 07/27] ocxl: Add functions to map/unmap LPC memory
To:     "Alastair D'Silva" <alastair@au1.ibm.com>, alastair@d-silva.org
Cc:     "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        "Oliver O'Halloran" <oohall@gmail.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Frederic Barrat <fbarrat@linux.ibm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Rob Herring <robh@kernel.org>,
        Anton Blanchard <anton@ozlabs.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@linux.vnet.ibm.com>,
        =?UTF-8?Q?C=c3=a9dric_Le_Goater?= <clg@kaod.org>,
        Anju T Sudhakar <anju@linux.vnet.ibm.com>,
        Hari Bathini <hbathini@linux.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kurz <groug@kaod.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Alexey Kardashevskiy <aik@ozlabs.ru>,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-nvdimm@lists.01.org, linux-mm@kvack.org
References: <20200221032720.33893-1-alastair@au1.ibm.com>
 <20200221032720.33893-8-alastair@au1.ibm.com>
From:   Andrew Donnellan <ajd@linux.ibm.com>
Date:   Mon, 24 Feb 2020 17:02:32 +1100
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On 21/2/20 2:27 pm, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@d-silva.org>
> 
> Add functions to map/unmap LPC memory
> 
> Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
> ---
>   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;

I'd prefer the comparison here to be:

   afu->config.lpc_mem_size == 0 &&
     afu->config.special_purpose_mem_size == 0

so a reader doesn't have to think about what this means.

> +
> +	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;

Maybe not for this series - hmm, I wonder if we should print a warning 
somewhere (maybe in read_afu_lpc_memory_info()?) if we see the case 
where (lpc_mem_offset > 0 && lpc_mem_size == 0). Likewise for special 
purpose?

> +		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);

What's the point of this function? A layer of indirection just in case 
we need it in future?

> +
> +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 d0c8c4838f42..ce0cac1da416 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

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
> 

-- 
Andrew Donnellan              OzLabs, ADL Canberra
ajd@linux.ibm.com             IBM Australia Limited