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From:   Rajan Vaja <RAJANV@xilinx.com>
To:     Sudeep Holla <sudeep.holla@arm.com>, Jolly Shah <JOLLYS@xilinx.com>
CC:     "ard.biesheuvel@linaro.org" <ard.biesheuvel@linaro.org>,
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        Tejas Patel <TEJASP@xilinx.com>
Subject: RE: [PATCH 0/2] arch: arm64: xilinx: Make zynqmp_firmware driver
 optional
Thread-Topic: [PATCH 0/2] arch: arm64: xilinx: Make zynqmp_firmware driver
 optional
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Date:   Mon, 13 Jan 2020 06:46:52 +0000
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Hi Sudeep,

Thanks for the reviewing patch.

> -----Original Message-----
> From: Sudeep Holla <sudeep.holla@arm.com>
> Sent: 10 January 2020 05:24 PM
> To: Jolly Shah <JOLLYS@xilinx.com>
> Cc: ard.biesheuvel@linaro.org; mingo@kernel.org; gregkh@linuxfoundation.o=
rg;
> matt@codeblueprint.co.uk; hkallweit1@gmail.com; keescook@chromium.org;
> dmitry.torokhov@gmail.com; Michal Simek <michals@xilinx.com>; Rajan Vaja
> <RAJANV@xilinx.com>; linux-arm-kernel@lists.infradead.org; linux-
> kernel@vger.kernel.org; Sudeep Holla <sudeep.holla@arm.com>; Tejas Patel
> <TEJASP@xilinx.com>
> Subject: Re: [PATCH 0/2] arch: arm64: xilinx: Make zynqmp_firmware driver
> optional
>=20
> EXTERNAL EMAIL
>=20
> On Thu, Jan 09, 2020 at 11:06:02AM -0800, Jolly Shah wrote:
> > From: Tejas Patel <tejas.patel@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.
> >
>=20
> 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  t=
here 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.

Thanks,
Rajan
> --
> Regards,
> Sudeep