Hi Arnd,
On 2014年09月09日 11:58, Arnd Bergmann wrote:
On Tuesday 09 September 2014 19:16:01 Lian Minghuan-B31939 wrote:
On 2014年09月09日 10:50, Arnd Bergmann wrote:
On Tuesday 09 September 2014 18:46:59 Lian Minghuan-B31939 wrote:
On 2014年09月09日 09:56, Arnd Bergmann wrote:
On Tuesday 09 September 2014 17:25:57 Lian Minghuan-B31939 wrote:
[Minghuan] I discussed with my colleague. They worry about performance
degradation if using regmap API,
because there are some fast device use scfg. We tend to use a simple way
to map andread/write scfg directly.
I see. In this case, I would probably create a separate msi controller
driver that owns the "fsl,ls1021a-scfg" device, and is referenced
through the "msi-parent" property in the pcie controller.
You can use of_pci_find_msi_chip_by_node() to get the msi_chip
instance and then connect that to your pci host. This will also
take care of the case where you may want to use the main GICv3
on a future SoC.
[Minghuan] There is something wrong with LS1021A MSI hardware that it
only supports one interrupt not 32 interrupts. Now, I do not want to
create a separate msi controller driver just for incorrect hardware.
I may provide complete MSI driver for the new hardware when it is ready.
Would you just leave out MSI support for the LS1021A PCIe variant?
I guess that's fine because all device drivers should also support
legacy interrupts and there is no performance gain in MSI in this
case.
[Minghuan] I have added MSI support for LS1021A PCIe just reserved 31
interrupts as used.
I don't understand your logic then. If LS1021A has an incorrect MSI
implementation, and you may want to reuse the PCIe driver with a
future chip that either includes a correct MSI implementation, or
with one that uses the GICv3 instead, isn't that even more reason
to split out the MSI support into a separate driver?
That way you can at least separate the normal code path from the
broken one and don't need any special run-time or compile-conditionals
beyond calling of_pci_find_msi_chip_by_node().
[Minghuan] The new MSI hardware implementation is not ready, I do not
know how to describe its dts node
and how to implement its driver. When it is ready, I will implement the
driver and add a workaround
for the current incorrect MSI. The current MSI driver is based on
pci-designware.
Arnd
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