Re: [PATCH 2/2] spi: qcom-geni: Add property to force GSI mode

[Pengyu Luo]

On Tue, Jun 30, 2026 at 8:28 PM Mukesh Savaliya
<mukesh.savaliya@xxxxxxxxxxxxxxxx> wrote:
>
>
>
> On 6/30/2026 3:36 PM, Pengyu Luo wrote:
> > On Tue, Jun 30, 2026 at 5:52 PM Mukesh Savaliya
> > <mukesh.savaliya@xxxxxxxxxxxxxxxx> wrote:
> >>
> >>
> >>
> >> On 6/29/2026 1:33 PM, Pengyu Luo wrote:
> >>> On Mon, Jun 29, 2026 at 1:36 PM Mukesh Savaliya
> >>> <mukesh.savaliya@xxxxxxxxxxxxxxxx> wrote:
> >>>>
> >>>> Hi Pengyu,
> >>>>
> >>>> On 6/15/2026 2:48 AM, Dmitry Baryshkov wrote:
> >>>>> On Sun, Jun 14, 2026 at 04:34:24PM +0800, Pengyu Luo wrote:
> >>>>>> Some devices (such as gaokun3) do not disable FIFO mode, causing the
> >>>>>> driver to fallback to FIFO mode by default. However, these platforms
> >>>>>> also support GSI mode, which is highly preferred for certain
> >>>>>> peripherals like SPI touchscreens to improve performance.
> >>>>>>
> >>>>>> Introduce the "qcom,force-gsi-mode" device property to hint and force
> >>>>>> the controller into GSI mode during initialization.
> >>>> Why to force ? You can directly configure in GSI mode. Note there are
> >>>> some configuration done prior to Linux bootup too.
> >>>
> >>> Sorry, I don't get it. how? I know there may be a qupfw, but it is
> >>> impossible for a normal user like me to generate one with GSI
> >>> preferred.
> >>>
> >> If firmware doesn't program in GSI, you can't have this working in GSI
> >> mode, its going to fail (and work with fallback). if it's programmed in
> >> GSI, anyway this will run in GSI mode. So why to add extra things
> >> without any usage ?
> >>
> >
> > What I can confirm is that fifo is not disabled on my device, and gsi
> > is definitely enabled (under windows, check the register
> > SE_GENI_DMA_MODE_EN), forcing the device to enable GSI mode on linux
> > works well.
> >
> Thanks  ! if GSI is already enabled, then why do you need forced gsi ?

I meant it is enabled on windows, not linux, and I think it is enabled
in the driver, geni_se_select_dma_mode() does it. On windows,
GENI_DMA_MODE_EN bit is set, but not on linux.

Yes, I have no doubt about below(as I drop DT part in V2), but the
GENI_IF_DISABLE_RO register only determines if fifo is disabled, if
not, why can't we use GSI?

> My point here - SW should only decide mode based on register read, not
> enforce by DT flag. As such it's not a SOC exposed, can't be overridden
> by user.

Best wishes,
Pengyu

> >>>
> >>>>>
> >>>>> Ideally, this should be decided by the SPI controller based on the
> >>>>> requirements. Another option would be to prefer GSI for all transfers if
> >>>>> it is available, ignoring the FIFO even if it is not disabled.
> >>>>>
> >>>> Yes, it should be decided in advance and configured accordingly for GSI
> >>>> vs non GSI mode. Because there would be limited set of GSI pipes, which
> >>>> will actually make must have GSI mode device run with FIFO mode.
> >>>>
> >>>> Why don't you decide prior and configure for GSI mode ? We don't need to
> >>>> change the current logic of deciding FIFO vs GSI.
> >>>>>>
> >>>>>> Signed-off-by: Pengyu Luo <mitltlatltl@xxxxxxxxx>
> >>>>>> ---
> >>>>>>     drivers/spi/spi-geni-qcom.c | 7 +++++++
> >>>>>>     1 file changed, 7 insertions(+)
> >>>>>>
> >>>>>
> >>>>
> >>
>