linux-kernel - Re: [PATCH] ipmi: kcs: Poll OBF briefly to reduce OBE latency

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Message-Id: <08c20621-e75d-4a72-82e6-b1980304e20a@app.fastmail.com>
Date:   Thu, 06 Oct 2022 09:42:57 +1030
From:   "Andrew Jeffery" <andrew@...id.au>
To:     openipmi-developer@...ts.sourceforge.net,
        "Corey Minyard" <minyard@....org>
Cc:     linux-aspeed@...ts.ozlabs.org, openbmc@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ipmi: kcs: Poll OBF briefly to reduce OBE latency

Hi Corey,

On Sat, 13 Aug 2022, at 00:17, Andrew Jeffery wrote:
> The ASPEED KCS devices don't provide a BMC-side interrupt for the host
> reading the output data register (ODR). The act of the host reading ODR
> clears the output buffer full (OBF) flag in the status register (STR),
> informing the BMC it can transmit a subsequent byte.
>
> On the BMC side the KCS client must enable the OBE event *and* perform a
> subsequent read of STR anyway to avoid races - the polling provides a
> window for the host to read ODR if data was freshly written while
> minimising BMC-side latency.

Just wondering whether you're happy to pick this one up? I haven't seen 
it hit the IPMI tree yet.

Cheers,

Andrew