RE: [EXTERNAL] Re: [meta-ti] [RFC|kirkstone] linux-ti-staging: add config preempt for am335x and am437x

["Balagopalakrishnan, Anand" <anandb@ti.com>]

Hi Denys,

This is only needed for v7 platforms like AM3 / AM4 and possibly AM57x also. CONFIG_PREEMPT is enabled by default on arm64 platforms like AM65x.

Praneeth will send a kernel patch for TI kernel. This meta-ti patch is meant to unblock anyone who wants to enable SGX drive in the meanwhile. 

Regards,
Anand

-----Original Message-----
From: Denys Dmytriyenko <denis@denix.org> 
Sent: Friday, September 15, 2023 1:25 AM
To: Balagopalakrishnan, Anand <anandb@ti.com>
Cc: meta-ti@lists.yoctoproject.org; Eatmon, Ryan <reatmon@ti.com>; Adivi, Sai Sree Kartheek <s-adivi@ti.com>; Gupta, Gyan <g-gupta@ti.com>; Khasim, Syed Mohammed <khasim@ti.com>; Pothukuchi, Vijay <vijayp@ti.com>; Bajjuri, Praneeth <praneeth@ti.com>
Subject: [EXTERNAL] Re: [meta-ti] [RFC|kirkstone] linux-ti-staging: add config preempt for am335x and am437x

On Thu, Sep 14, 2023 at 03:36:18PM -0400, Denys Dmytriyenko wrote:
> On Thu, Sep 14, 2023 at 10:40:26PM +0530, Anand Balagopalakrishnan via lists.yoctoproject.org wrote:
> > SGX needs a preemptible kernel. CONFIG_PREEMPT has always been 
> > enabled on TI Linux kernels upto K5.1.
> > 
> > This is enabled on AM65x by default but missed out AM335x and AM437x.
> > Add a kernel config fragment to enable config preempt.
> 
> Hi, Anand,
> 
> Is this only needed for am335x and am437x, as the subject suggests? If 
> so, why the code adds the config fragment to all platforms?
> 
> Second question - historically this has been enabled in the TI kernel itself. 
> Why not do it like that again, why add the fragment to the OE metadata 
> instead of keeping it in-tree? How the distro-agnostic approach would be handled?
> 
> 
> > Signed-off-by: Anand Balagopalakrishnan <anandb@ti.com>
> > ---
> >  .../linux/files/configs/config-preempt.cfg           | 12 ++++++++++++
> >  .../recipes-kernel/linux/linux-ti-staging_6.1.bb     |  1 +
> >  2 files changed, 13 insertions(+)
> >  create mode 100644 
> > meta-ti-bsp/recipes-kernel/linux/files/configs/config-preempt.cfg
> > 
> > diff --git 
> > a/meta-ti-bsp/recipes-kernel/linux/files/configs/config-preempt.cfg 
> > b/meta-ti-bsp/recipes-kernel/linux/files/configs/config-preempt.cfg
> > new file mode 100644
> > index 00000000..c1e5ad7d
> > --- /dev/null
> > +++ b/meta-ti-bsp/recipes-kernel/linux/files/configs/config-preempt.
> > +++ cfg
> 
> This is not the right location for the file. You want to add to the 
> linux-ti-staging-rt-6.1/ directory, since you are only using it from 
> the corresponding linux-ti-staging_6.1.bb recipe.

Sorry, typo here - linux-ti-staging-6.1/ directory, if it's not RT-specific.

> 
> > @@ -0,0 +1,12 @@
> > +CONFIG_PREEMPT_BUILD=y
> > +# CONFIG_PREEMPT_NONE is not set
> > +CONFIG_PREEMPT=y
> > +CONFIG_PREEMPT_COUNT=y
> > +CONFIG_PREEMPTION=y
> > +CONFIG_PREEMPT_RCU=y
> > +CONFIG_TASKS_RCU_GENERIC=y
> > +CONFIG_TASKS_RCU=y
> > +CONFIG_UNINLINE_SPIN_UNLOCK=y
> > +# CONFIG_CEC_GPIO is not set
> > +CONFIG_DEBUG_PREEMPT=y
> > +# CONFIG_PREEMPT_TRACER is not set
> > diff --git 
> > a/meta-ti-bsp/recipes-kernel/linux/linux-ti-staging_6.1.bb 
> > b/meta-ti-bsp/recipes-kernel/linux/linux-ti-staging_6.1.bb
> > index 8a883878..0ee63358 100644
> > --- a/meta-ti-bsp/recipes-kernel/linux/linux-ti-staging_6.1.bb
> > +++ b/meta-ti-bsp/recipes-kernel/linux/linux-ti-staging_6.1.bb
> > @@ -33,6 +33,7 @@ PR = "${MACHINE_KERNEL_PR}"
> >  
> >  KERNEL_GIT_URI ?= "git://git.ti.com/git/ti-linux-kernel/ti-linux-kernel.git"
> >  KERNEL_GIT_PROTOCOL = "https"
> > +KERNEL_CONFIG_FRAGMENTS += "${WORKDIR}/config-preempt.cfg"
> 
> Since this file is out-of-tree and in the OE metadata, it would also 
> require listing it in SRC_URI.
> 
> 
> >  SRC_URI += "${KERNEL_GIT_URI};protocol=${KERNEL_GIT_PROTOCOL};branch=${BRANCH} \
> >              file://defconfig"
> >  
> > --
> > 2.34.1