linux-kernel - Re: [EXT] Re: [PATCH RFC net-next 03/19] net: mvpp2: add CM3 SRAM memory map

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Message-ID: <X/s80rM1HBFrkHyl@lunn.ch>
Date:   Sun, 10 Jan 2021 18:43:46 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Stefan Chulski <stefanc@...vell.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "thomas.petazzoni@...tlin.com" <thomas.petazzoni@...tlin.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Nadav Haklai <nadavh@...vell.com>,
        Yan Markman <ymarkman@...vell.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "mw@...ihalf.com" <mw@...ihalf.com>,
        "rmk+kernel@...linux.org.uk" <rmk+kernel@...linux.org.uk>,
        "atenart@...nel.org" <atenart@...nel.org>
Subject: Re: [EXT] Re: [PATCH RFC net-next  03/19] net: mvpp2: add CM3 SRAM
 memory map

> > Should there be -EPROBE_DEFER handling in here somewhere? The SRAM is a
> > device, so it might not of been probed yet?
> 

> No, firmware probed during bootloader boot and we can use SRAM. SRAM
> memory can be safely used.

A previous patch added:

+               CP11X_LABEL(cm3_sram): cm3@...000 {
+                       compatible = "mmio-sram";
+                       reg = <0x220000 0x800>;
+                       #address-cells = <1>;
+                       #size-cells = <1>;
+                       ranges = <0 0x220000 0x800>;
+               };
+

So it looks like the SRAM is a device, in the linux driver model. And
there is a driver for this, driver/misc/sram.c. How do you know this
device has been probed before the Ethernet driver?

       Andrew