On 01.12.14 23:53, Stuart Yoder wrote:
>
>
>> -----Original Message-----
>> From: Alexander Graf [mailto:ag...@suse.de]
>> Sent: Thursday, November 27, 2014 10:14 AM
>> To: Rivera Jose-B46482; gre...@linuxfoundation.org; a...@arndb.de;
>> linux-kernel@vger.kernel.org
>> Cc: Yoder Stuart-B08248; Phillips Kim-R1AAHA; Wood Scott-B07421; Hamciuc
>> Bogdan-BHAMCIU1; Marginean
>> Alexandru-R89243; Thorpe Geoff-R01361; Sharma Bhupesh-B45370; Erez
>> Nir-RM30794; Schmitt Richard-B43082
>> Subject: Re: [PATCH 1/3 v4] drivers/bus: Added Freescale Management Complex
>> APIs
>>
>>
>>
>> On 13.11.14 18:54, J. German Rivera wrote:
>>> APIs to access the Management Complex (MC) hardware
>>> module of Freescale LS2 SoCs. This patch includes
>>> APIs to check the MC firmware version and to manipulate
>>> DPRC objects in the MC.
>>>
>>> Signed-off-by: J. German Rivera <german.riv...@freescale.com>
>>> Signed-off-by: Stuart Yoder <stuart.yo...@freescale.com>
>>
>> [...]
>>
>>> +/**
>>> + * Creates an MC I/O object
>>> + *
>>> + * @dev: device to be associated with the MC I/O object
>>> + * @mc_portal_phys_addr: physical address of the MC portal to use
>>> + * @mc_portal_size: size in bytes of the MC portal
>>> + * @flags: flags for the new MC I/O object
>>> + * @new_mc_io: Area to return pointer to newly created MC I/O object
>>> + *
>>> + * Returns '0' on Success; Error code otherwise.
>>> + */
>>> +int __must_check fsl_create_mc_io(struct device *dev,
>>> + phys_addr_t mc_portal_phys_addr,
>>> + uint32_t mc_portal_size,
>>> + uint32_t flags, struct fsl_mc_io **new_mc_io)
>>> +{
>>> + struct fsl_mc_io *mc_io;
>>> + void __iomem *mc_portal_virt_addr;
>>> + struct resource *res;
>>> +
>>> + mc_io = devm_kzalloc(dev, sizeof(*mc_io), GFP_KERNEL);
>>> + if (mc_io == NULL)
>>> + return -ENOMEM;
>>> +
>>> + mc_io->dev = dev;
>>> + mc_io->flags = flags;
>>> + mc_io->portal_phys_addr = mc_portal_phys_addr;
>>> + mc_io->portal_size = mc_portal_size;
>>> + res = devm_request_mem_region(dev,
>>> + mc_portal_phys_addr,
>>> + mc_portal_size,
>>> + "mc_portal");
>>> + if (res == NULL) {
>>> + dev_err(dev,
>>> + "devm_request_mem_region failed for MC portal %#llx\n",
>>> + mc_portal_phys_addr);
>>> + return -EBUSY;
>>> + }
>>> +
>>> + mc_portal_virt_addr = devm_ioremap_nocache(dev,
>>> + mc_portal_phys_addr,
>>> + mc_portal_size);
>>
>> While I can't complain about the device itself, I will note that I think
>> it's a pretty bad design decision to expose actual host physical
>> addresses in the protocol.
>
> I tend to agree. I'll look into creating a proposed change to the
> architecture
> to have the MC communicate a physical offset of some kind.
>
>> Basically this means that you won't be able to pass a full MC complex
>> into a guest, even if you could virtualize IRQ and DMA access unless you
>> map it at the exact same location as the host's MC complex.
>
> Right. But is that really an issue in practice?
Well, it obviously depends on what you're trying to do. For everything
that's envisioned today I don't think it's a problem, but I like to
stick to the "know as little as you have to know" rule when it comes to
communication protocols.
>> Could we at least add a "ranges" property to the MC device description
>> and check whether the physical addresses we get are within that range -
>> if nothing else, at least as sanity check? Then maybe add some calls in
>> the next version that act on that range rather than actual host physical
>> addresses?
>
> So you mean something like:
>
> fsl_mc: fsl-mc@80c000000 {
> compatible = "fsl,qoriq-mc";
> #stream-id-cells = <2>;
> reg = <0x00000008 0x0c000000 0 0x40>, /* MC portal base */
> <0x00000000 0x08340000 0 0x40000>; /* MC control reg */
> ranges = <0x8 0x0 0x8 0x0 0x20000000>;
> lpi-parent = <&its>;
> };
>
> The physical addresses returned by the MC fall into a 512MB "portal"
> region at 0x8_0000_0000 in the physical address map. For now map it 1:1, but
> in the
> future it could become:
> ranges = <0x0 0x0 0x8 0x0 0x20000000>;
>
> ...if I can get the hardware architecture changed.
Yup, I think that makes things a lot less error prone - you don't
randomly access any pointer the device tells you to access :).
Alex
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