Re: [PATCH] arm64: defconfig: Enable Qualcomm UFS and QMP UFS PHY drivers as built-in

[Kuldeep Singh]

On 18-04-2026 04:29, Dmitry Baryshkov wrote:
> On Fri, Apr 17, 2026 at 06:37:06PM +0800, Shawn Guo wrote:
> > On Fri, Apr 17, 2026 at 10:44:20AM +0200, Krzysztof Kozlowski wrote:
> > > On 17/04/2026 10:37, Shawn Guo wrote:
> > > > On Fri, Apr 17, 2026 at 10:14:23AM +0200, Krzysztof Kozlowski wrote:
> > > > > On 17/04/2026 05:55, Shawn Guo wrote:
> > > > > > UFS is the primary storage for Linux rootfs across the breadth of
> > > > > > Qualcomm development boards - Mobile, Automotive and IoT.  With
> > > > > > Qualcomm UFS host controller driver (SCSI_UFS_QCOM) and the UFS PHY
> > > > > > driver (PHY_QCOM_QMP_UFS) as modules, developers need an initramfs
> > > > >
> > > > > Yes, you always need initramfs and every developer has it.
> > > > >
> > > > > > to boot from UFS, which adds friction to daily development workflows.
> > > > >
> > > > > No friction, it's both standard, easy and all of Qualcomm and Linaro
> > > > > developers have it solved long time ago.
> > > >
> > > > I'm looking at a kernel regression by running git bisect, where kernel
> > > > version string varies for every single boot.  How do you usually deal
> > > > with it by using initramfs?
> > >
> > > No difference from every other build and boot? I build kernel and the
> > > same step I have initramfs with modules. Whether I bisect or build
> > > kernel for normal boot is exactly the same.
> > >
> > > The only difference is `git bisect good`.
> >
> > So we have to rebuild initramfs for every single bisect.  But isn't
> > built-in make it easier and faster for the whole bisect process?
>
> No. Insted you package modules as a separate .cpio.gz archive,
> concatenate it with the initramfs and boot the kernel.
>
> > It's especially useful for tasks where we do not even need to make modules,
> > like debugging built-in drivers.
> >
> > > > If using initramfs is standard and easy, I wonder why Qualcomm QLI
> > > > (meta-qcom) kernel has UFS drivers as built-in.
> > >
> > > This I don't know. Distros do various things, but of course there might
> > > be an argument I do not know (e.g. like it was why distros do not make
> > > IPV6 a module).
> >
> > We can consult internally, but saving use of initramfs could be part of
> > it, I would guess.
>
> Having the meta-qcom hat on:
> - If we know that the kernel is going to be used on Qualcomm hardware,
>    it makese sense to enable necessary drivers as built-in to save time,
>    boot time and to ease overall integration.
>
> - Having the general defconfig, it doesn't make sense to make users of
>    all other platforms suffer and loose their memory by having
>    Qualcomm-specific drivers loaded, if that's not an absolute
>    requirement.

Then it makes sense to make CONFIG_MSM_SDHCI or 
CONFIG_MSM_SDHCI_MSM(qcom specific config) as module too?
https://elixir.bootlin.com/linux/v7.0/source/arch/arm64/configs/defconfig#L1279

Not sure why it's enabled as builtin for all vendors.

--
Regards
Kuldeep