RE: [PATCH v2 04/15] PCI: xilinx: Don't allocate extra memory for the MSI capture address

[Bharat Kumar Gogada]

Thanks Marc for the patch.
> Subject: [PATCH v2 04/15] PCI: xilinx: Don't allocate extra memory for the
> MSI capture address
> 
> A long cargo-culted behaviour of PCI drivers is to allocate memory to obtain
> an address that is fed to the controller as the MSI capture address (i.e. the
> MSI doorbell).
> 
> But there is no actual requirement for this address to be RAM.
> All it needs to be is a suitable aligned address that will
> *not* be DMA'd to.
> 
> Use the physical address of the 'port' data structure as the MSI capture
> address.
> 
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
>  drivers/pci/controller/pcie-xilinx.c | 18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)

...
> -	msg.address_hi = 0;
> -	msg.address_lo = msg_addr;
> +	msg.address_hi = upper_32_bits(msg_addr);
> +	msg.address_lo = lower_32_bits(msg_addr);

The XILINX_PCIE_REG_MSIBASE2 register expects 4KB aligned address.
The lower 12-bits are always set to 0 in this register. So we need to mask the address 
while programming address to EP.

#define XILINX_PCIE_MSI_ADDR_MASK       GENMASK(31, 12)
msg.address_lo = lower_32_bits(msg_addr) & XILINX_PCIE_MSI_ADDR_MASK;


>  	msg.data = irq;
>

Regards,
Bharat