linux-kernel - Re: PCIe MSI address is not written at pci_enable_msi

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Date:	Tue, 12 Jul 2016 16:56:42 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	Arnd Bergmann <arnd@...db.de>, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: PCIe MSI address is not written at pci_enable_msi_range call

On 11/07/16 10:33, Bharat Kumar Gogada wrote:
> Hi Marc,
> 
> Thanks for the reply.
> 
> From PCIe Spec:
> MSI Enable Bit:
> If 1 and the MSI-X Enable bit in the MSI-X Message
> Control register (see Section 6.8.2.3) is 0, the
> function is permitted to use MSI to request service
> and is prohibited from using its INTx# pin.
> 
> From Endpoint perspective, MSI Enable = 1 indicates MSI can be used which means MSI address and data fields are available/programmed.
> 
> In our SoC whenever MSI Enable goes from 0 --> 1 the hardware latches onto MSI address and MSI data values.
> 
> With current MSI implementation in kernel, our SoC is latching on to incorrect address and data values, as address/data
> are updated much later than MSI Enable bit.

As a side question, how does setting the affinity work on this end-point
if this involves changing the address programmed in the MSI registers?
Do you expect the enabled bit to be toggled to around the write?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...