lkml.org 
[lkml]   [2018]   [Mar]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [PATCH v5 3/4] drivers: firmware: xilinx: Add sysfs interface
Date
Hi Sudeep,


> -----Original Message-----
> From: Sudeep Holla [mailto:sudeep.holla@arm.com]
> Sent: Thursday, March 01, 2018 6:44 AM
> To: Jolly Shah <JOLLYS@xilinx.com>
> Cc: ard.biesheuvel@linaro.org; mingo@kernel.org;
> gregkh@linuxfoundation.org; matt@codeblueprint.co.uk;
> hkallweit1@gmail.com; keescook@chromium.org;
> dmitry.torokhov@gmail.com; michal.simek@xilinx.com; robh+dt@kernel.org;
> mark.rutland@arm.com; Sudeep Holla <sudeep.holla@arm.com>; Rajan Vaja
> <RAJANV@xilinx.com>; linux-arm-kernel@lists.infradead.org; linux-
> kernel@vger.kernel.org; devicetree@vger.kernel.org; Jolly Shah
> <JOLLYS@xilinx.com>
> Subject: Re: [PATCH v5 3/4] drivers: firmware: xilinx: Add sysfs interface
>
>
>
> On 20/02/18 19:21, Jolly Shah wrote:
> > Add Firmware-ggs sysfs interface which provides read/write interface
> > to global storage registers.
> >
> > Signed-off-by: Jolly Shah <jollys@xilinx.com>
> > Signed-off-by: Rajan Vaja <rajanv@xilinx.com>
> > ---
> > .../ABI/stable/sysfs-driver-zynqmp-firmware | 50 ++++
> > drivers/firmware/xilinx/zynqmp/Makefile | 2 +-
> > drivers/firmware/xilinx/zynqmp/firmware-ggs.c | 297
> +++++++++++++++++++++
> > drivers/firmware/xilinx/zynqmp/firmware.c | 13 +
> > include/linux/firmware/xilinx/zynqmp/firmware.h | 2 +
> > 5 files changed, 363 insertions(+), 1 deletion(-) create mode 100644
> > Documentation/ABI/stable/sysfs-driver-zynqmp-firmware
> > create mode 100644 drivers/firmware/xilinx/zynqmp/firmware-ggs.c
> >
> > diff --git a/Documentation/ABI/stable/sysfs-driver-zynqmp-firmware
> > b/Documentation/ABI/stable/sysfs-driver-zynqmp-firmware
> > new file mode 100644
> > index 0000000..b04727a
> > --- /dev/null
> > +++ b/Documentation/ABI/stable/sysfs-driver-zynqmp-firmware
> > @@ -0,0 +1,50 @@
> > +What: /sys/devices/platform/zynqmp-firmware/ggs> +Date:
> January 2018
> > +KernelVersion: 4.15.0
> > +Contact: "Jolly Shah" <jollys@xilinx.com>
> > +Description:
> > + Read/Write PMU global general storage register value,
> > + GLOBAL_GEN_STORAGE{0:3}.
> > + Global general storage register that can be used
> > + by system to pass information between masters.
> > +
>
> What kind of information ? Is there any semantics for that ?
> Why does EEMI lack APIs for that if it's critical, giving access to such information
> to userspace may not be good idea.
>

These are for general use. Information being passed can be application specific.
Sysfs call underneath maps to EEMI ioctl call to read/write these registers.

> > + The register is reset during system or power-on
> > + resets. Three registers are used by the FSBL and
> > + other Xilinx software products: GLOBAL_GEN_STORAGE{4:6}.
> > +
>
> FSBL ?
>
> For what is it used ?

There are total 8 such registers. 4 are reserved for customer application. Other 4 are being used by Xilinx sw products like FSBL.
FSBL is using it to pass handoff information to other master.

>
> > + Usage:
> > + # cat /sys/.../zynqmp-firmware/ggs0
> > + # echo <mask> <value> > /sys/.../zynqmp-firmware/ggs0
> > +
> > + Example:
> > + # cat /sys/.../zynqmp-firmware/ggs0
> > + # echo 0xFFFFFFFF 0x1234ABCD > /sys/.../zynqmp-
> firmware/ggs0
> > +
> > +Users: Xilinx
> > +
> > +What: /sys/devices/platform/zynqmp-firmware/pggs*
> > +Date: January 2018
> > +KernelVersion: 4.15.0
> > +Contact: "Jolly Shah" <jollys@xilinx.com>
> > +Description:
> > + Read/Write PMU persistent global general storage register
> > + value, PERS_GLOB_GEN_STORAGE{0:3}.
> > + Persistent global general storage register that
> > + can be used by system to pass information between
> > + masters.
> > +
>
> Ditto
>
> > + This register is only reset by the power-on reset
> > + and maintains its value through a system reset.
> > + Four registers are used by the FSBL and other Xilinx
> > + software products: PERS_GLOB_GEN_STORAGE{4:7}.
> > + Register is reset only by a POR reset.
> > +
>
> Ditto
>
> --
> Regards,
> Sudeep
\
 
 \ /
  Last update: 2018-03-07 23:04    [W:0.091 / U:5.492 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site