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From: Jeremy Kerr <firstname.lastname@example.org>
To: ChiaWei Wang <email@example.com>,
Cc: Morris Mao <firstname.lastname@example.org>,
Ryan Chen <email@example.com>
Subject: Re: [PATCH v4 3/4] soc: aspeed: Add eSPI driver
Date: Thu, 09 Sep 2021 09:52:43 +0800 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
> Yes, there is security concern using HW mode.
> Our designer is considering to remove the HW mode support in the next
> generation of Aspeed SoCs.
> So far we haven't encountered a scenario demanding HW mode.
Great to hear :) can we unconditionally set ESPI000 in the driver
> > With than in mind, if we're disabling hardware mode - what does the
> > direction control setting effect when we're in software mode
> > (ESPICTRL == 1)? Does it even matter?
> Yes, the direction matters even in SW mode.
> When the direction is 'master-to-slave' and the GPIO value is updated
> by the Host through PUT_VW, a VW interrupt is trigger to notify BMC.
> For the 'slave-to-master' GPIO, a alert is generated to notify the
> Host to issue GET_VW for the GPIO value updated by the BMC by
OK, but the datasheet mentions that ESPICFG804 is only applicable when
ESPI000 = 0, or is that not the case?
But based on what you've said: yes, it sounds like the generic gpiodev
parts won't be useful for this.
> > Separate from this: I'm also proposing that we represent the system
> > event VWs
> > as gpiodevs as well.
> > > A raw packet, primitive interface should have better flexibility
> > > to
> > > manage MCTP packets over the OOB channel.
> > OK, let me phrase this differently: can the OOB channel be used for
> > anything other than SMBus messaging? Is it useful to provide an
> > interface that isn't a standard SMBus/i2c device?
> Yes, the PCH spec. also defines two additional packet format for an
> eSPI slave to retrieve PCH Temperature Data and RTC time.
> It should be trivial to prepare a byte buffer in that format and send
> it through the raw packet interface.
> > If you need custom uapi definitions for this driver, that might be
> > okay, but it's going to be more work for you (to define an interface
> > that can be supported long-term), rather than using standard
> > infrastructure that already exists.
> Thus I suggested that we can refer to the IPMI KCS BMC driver, which
> supports the selection of different user interfaces, RAW or IPMI.
Yep, but the KCS "raw" register set is standardised as part of the IPMI
spec too, which helps to define a stable user API. We don't have that in
Overall though, if you want to start with the "low-level" API, then
introduce "enhanced" functionality - like an actual SMBus driver -
alongside that, then that sounds like an OK approach.
> If IOCTL is considered to be not user friendly or magic code
> polluting, file-based read/write on the miscdevice node is also an
It's not really my decision to make, but a read/write event interface
would seem to be more consistent to me. Is there an obvious event format
that would be common across all channels, perhaps? We'd probably also
need a poll too - to make use of incoming events, like master-to-slave
VW changes, perhaps?
next prev parent reply other threads:[~2021-09-09 1:52 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-01 3:30 [PATCH v4 0/4] arm: aspeed: Add eSPI support Chia-Wei Wang
2021-09-01 3:30 ` [PATCH v4 1/4] dt-bindings: aspeed: Add eSPI controller Chia-Wei Wang
2021-09-01 3:30 ` [PATCH v4 2/4] MAINTAINER: Add ASPEED eSPI driver entry Chia-Wei Wang
2021-09-01 3:30 ` [PATCH v4 3/4] soc: aspeed: Add eSPI driver Chia-Wei Wang
2021-09-02 3:29 ` Jeremy Kerr
2021-09-02 6:44 ` ChiaWei Wang
2021-09-02 7:04 ` Jeremy Kerr
2021-09-06 1:19 ` ChiaWei Wang
2021-09-06 3:16 ` Jeremy Kerr
2021-09-08 9:16 ` ChiaWei Wang
2021-09-09 1:52 ` Jeremy Kerr [this message]
2021-09-10 3:23 ` ChiaWei Wang
2021-09-01 3:30 ` [PATCH v4 4/4] ARM: dts: aspeed: Add eSPI node Chia-Wei Wang
2021-11-10 11:21 ` Andrei Kartashev
2021-11-11 1:55 ` ChiaWei Wang
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