linux-kernel - Re: [PATCH 0/4] cxl: Add a firmware update mechanism and cxl

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Date:   Fri, 2 Jun 2023 17:48:37 +0000
From:   "Verma, Vishal L" <vishal.l.verma@...el.com>
To:     "dave@...olabs.net" <dave@...olabs.net>
CC:     "Jiang, Dave" <dave.jiang@...el.com>,
        "Schofield, Alison" <alison.schofield@...el.com>,
        "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Weight, Russell H" <russell.h.weight@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "bwidawsk@...nel.org" <bwidawsk@...nel.org>,
        "Weiny, Ira" <ira.weiny@...el.com>
Subject: Re: [PATCH 0/4] cxl: Add a firmware update mechanism and cxl_test
 emulation

On Mon, 2023-04-24 at 10:39 -0700, Davidlohr Bueso wrote:
> On Fri, 21 Apr 2023, Vishal Verma wrote:
> 
> > The poll interval for the Transfer FW command is arbitrarily set at 1
> > second, and a poll count of 300, giving us a total wait time of five
> > minutes before which each slice of the transfer times out. This seems
> > like a good mix of responsiveness and a total wait - the spec doesn't
> > have any guidance on any upper or lower bounds for this. This likely
> > does not need to be user-configurable, so for now it is just hard-coded
> > in the driver.
> 
> Nothing against this, just thinking that in general, but we should
> probably limit the poll interval to CXL_MAILBOX_TIMEOUT_MS. I'm not
> sure, however, what would be a proper value across all commands. Or
> would having this limit be per-cmd make more sense instead?
> 
Sorry I missed this comment earlier - are these actually related? The
mailbox timeout just waits for the doorbell, which in the case of a
background command would just indicate successful submission. The poll
interval is just how frequently we want to check the status of the
background command. I assume this could be set to something longer than
the mailbox ready timeout, especially if we know it will be a long
running command.