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

[Pengyu Luo]

On Fri, Jun 26, 2026 at 11:34 PM Konrad Dybcio
<konrad.dybcio@xxxxxxxxxxxxxxxx> wrote:
>
> On 6/25/26 11:06 AM, Mukesh Savaliya wrote:
> > Hi Konrad, sorry for late response.
> >
> > On 6/15/2026 5:12 PM, Konrad Dybcio wrote:
> >> On 6/15/26 6:25 AM, Pengyu Luo wrote:
> >>> On Mon, Jun 15, 2026 at 5:18 AM Dmitry Baryshkov
> >>> <dmitry.baryshkov@xxxxxxxxxxxxxxxx> 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.
> >>>>
> >>>> 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.
> >>>>
> >>>
> >>> I have read reviews. Can we check if the compatible
> >>> "qcom,sm6350-gpi-dma" is in DT? If the gpi dma controller is
> >>> presented, then we enable GSI mode.
> >>
> >>
> >> This hunk is very odd:
> >>
> >> /*
> >>   * in case of failure to get gpi dma channel, we can still do the
> >>   * FIFO mode, so fallthrough
> >>   */
> >> dev_warn(mas->dev, "FIFO mode disabled, but couldn't get DMA, fall back to FIFO mode\n");
> >>
> >> In my understanding, GSI DMA mode is always preferable. +Mukesh, do
> >> you have any insights?
> >>
> > GSI mode is preferable but if for some reason it fails, we try to continue with the FIFO mode. Just fallback mechanism.
>
> So, would making GSI the default and FIFO the fallback option
> sound good?
>

Yes, I have sent v2, please check here
https://lore.kernel.org/linux-arm-msm/20260616122605.668908-1-mitltlatltl@xxxxxxxxx

Best wishes,
Pengyu

> Konrad
>