[PATCH 0/2] arch: arm64: xilinx: Make zynqmp_firmware driver optional

Rajan Vaja RAJANV at xilinx.com
Sun Jan 12 22:46:52 PST 2020

Hi Sudeep,

Thanks for the reviewing patch.

> -----Original Message-----
> From: Sudeep Holla <sudeep.holla at arm.com>
> Sent: 10 January 2020 05:24 PM
> To: Jolly Shah <JOLLYS at xilinx.com>
> Cc: ard.biesheuvel at linaro.org; mingo at kernel.org; gregkh at linuxfoundation.org;
> matt at codeblueprint.co.uk; hkallweit1 at gmail.com; keescook at chromium.org;
> dmitry.torokhov at gmail.com; Michal Simek <michals at xilinx.com>; Rajan Vaja
> <RAJANV at xilinx.com>; linux-arm-kernel at lists.infradead.org; linux-
> kernel at vger.kernel.org; Sudeep Holla <sudeep.holla at arm.com>; Tejas Patel
> <TEJASP at xilinx.com>
> Subject: Re: [PATCH 0/2] arch: arm64: xilinx: Make zynqmp_firmware driver
> optional
> On Thu, Jan 09, 2020 at 11:06:02AM -0800, Jolly Shah wrote:
> > From: Tejas Patel <tejas.patel at xilinx.com>
> >
> > Zynqmp firmware driver requires firmware to be present in system.
> > Zynqmp firmware driver will crash if firmware is not present in system.
> > For example single arch QEMU, may not have firmware, with such setup
> > Linux booting fails.
> >
> > So make zynqmp_firmware driver as optional to disable it if user don't
> > have firmware in system.
> >
> Why can't it be detected runtime ? How do you handle single binary if you
> make this compile time option ?
[Rajan] There is PMU register which indicates if firmware is present or not, but in case of single arch QEMU that register will not be available so  there is no way to detect if firmware is present or not from Linux.
Linux firmware crashes while arm_smccc_smc() call for firmware, but before this call there is no way  to identify if firmware is present or not. So we are just giving user an option if they want to use it on single arch
Platform they can disable firmware driver.

> --
> Regards,
> Sudeep

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