linux-kernel - Re: [PATCH] firmware: wake all waiters

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Message-ID: <20170626191009.0c11eed0@cakuba.netronome.com>
Date:   Mon, 26 Jun 2017 19:10:09 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     Ming Lei <ming.lei@...hat.com>, yi1.li@...ux.intel.com,
        takahiro.akashi@...aro.org, nbroeking@...com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        mfuzzey@...keon.com, ebiederm@...ssion.com,
        dmitry.torokhov@...il.com, wagi@...om.org, dwmw2@...radead.org,
        jewalt@...innovations.com, rafal@...ecki.pl,
        arend.vanspriel@...adcom.com, rjw@...ysocki.net, atull@...nel.org,
        moritz.fischer@...us.com, pmladek@...e.com,
        johannes.berg@...el.com, emmanuel.grumbach@...el.com,
        luciano.coelho@...el.com, luto@...nel.org,
        torvalds@...ux-foundation.org, keescook@...omium.org,
        dhowells@...hat.com, pjones@...hat.com, hdegoede@...hat.com,
        alan@...ux.intel.com, tytso@....edu, paul.gortmaker@...driver.com,
        mtosatti@...hat.com, mawilcox@...rosoft.com,
        stephen.boyd@...aro.org, markivx@...eaurora.org,
        linux-kernel@...r.kernel.org, oss-drivers@...ronome.com
Subject: Re: [PATCH] firmware: wake all waiters

On Mon, 26 Jun 2017 23:20:36 +0200, Luis R. Rodriguez wrote:
> > In that case we will make them all use the same struct firmware_buf.
> > When wake up happens make sure it's propagated to all of them.
> > 
> > Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>  
> 
> There's a slew of bugs lurking here though!
> 
> As noted the reported Intel driver issues still need other fixes, one was the
> fw_state_done() on the direct filesystem lookup mechanism [1], and that may be
> a regression since direct filesystem loading was added, and even secondary
> requests would seem to just wait forever (MAX_SCHEDULE_TIMEOUT); the combination
> of both fixes should fix your reported issue.
> 
> Do you intend on submitting those changes as well ? There's still *other* bugs
> with this feature though... Knowing if you will follow up with further fixes
> will be appreciated.

No, I don't have any more fixes in my tree right now :)  What I'm
looking towards implementing is actually a ability for NICs to load
default FW but then enable users to load different FW on their request. 

The problem is that advanced NICs are quite programmable [1] and
depending on use case one may want to load different firmware files.
It's slightly close to the FPGA use case, only with FPGA people don't
expect much plug and play, and with NICs the default mode after boot
must be "look as much as a standard NIC as possible".  Then loading
"advanced"/hand crafted firmware can turn more interesting features on.

The FW loading we have now in drivers/net/ethernet/netronome/nfp is
requesting default FW and returning -EPROBE_DEFER if not found.  Now I
need to find a way to allow users to "push" whatever advanced FW they
have into the NIC after/during boot.

Current firmware subsystem doesn't seem to cater to this use case to
well.  I have to look at the FPGA-related code.  The three main
problems to solve are:
 - how to stay bound and retry the direct default FW load until rootfs
   is mounted (equivalent to when -EPROBE_DEFER would give up);
 - how to expose permanent FW loading sysfs interface which won't
   disappear after the first -1/1 is written to .../loading;
 - how to make sure different cards, which request the same file name
   can be served different default firmwares...


Thanks for the improved commit message!

[1] HW links:
https://www.hotchips.org/wp-content/uploads/hc_archives/hc25/HC25.60-Networking-epub/HC25.27.620-22nm-Flow-Proc-Stark-Netronome.pdf
https://www.netronome.com/media/pdfs/NFP_Programming_Model_h6vxM7Y.pdf
http://open-nfp.org/resources/