linux-kernel - Re: [PATCH] arm: Enlarge IO_SPACE

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Date:   Tue, 11 May 2021 04:32:34 +0200
From:   Ansuel Smith <ansuelsmth@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Russell King <linux@...linux.org.uk>,
        Jonathan Corbet <corbet@....net>,
        Ard Biesheuvel <ardb@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Abbott Liu <liuwenliang@...wei.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm: Enlarge IO_SPACE_LIMIT needed for some SoC

On Tue, May 11, 2021 at 03:24:29AM +0100, Matthew Wilcox wrote:
> On Tue, May 11, 2021 at 04:16:54AM +0200, Ansuel Smith wrote:
> > Ipq8064 SoC requires larger IO_SPACE_LIMIT on second and third pci port.
> 
> Do you really?  I mean, yes, theoretically, I understand it, the
> hardware supports 64kB of I/O port space per root port.  But I/O
> port space is rather deprecated these days.  My laptop has precisely
> two devices with I/O ports, one with 64 bytes and the other with 32
> bytes.  Would you really suffer by allocating 16kB of I/O port
> space to each root port?

We were talking about this in the other wrong patch. I also think this
much space looks wrong. The current ipq806x dts have this space so it's
actually broken from a long time. The only reason pci worked before was
because the pci driver didn't actually check if the settings were right.
New kernel introduced more checks and this problem showed up. (to be
more precise, the pci port are commonly used by the ath10k wifi and the
second ath10k wifi fails to init because of this problem)
If you can give me any hint on how to check if the space can be reduced
I would be very happy to investigate it.
In the driver I notice that the max buffer is set to 2k, could be this a
hint?