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

[Mukesh Savaliya <mukesh.savaliya@oss.qualcomm.com>]

Hi Konrad,

On 7/2/2026 6:14 PM, Konrad Dybcio wrote:
> On 7/2/26 2:39 PM, Konrad Dybcio wrote:
>> On 6/30/26 12:06 PM, Pengyu Luo wrote:
>>> On Tue, Jun 30, 2026 at 5:52 PM Mukesh Savaliya
>>> <mukesh.savaliya@oss.qualcomm.com> wrote:
>>>>
>>>>
>>>>
>>>> On 6/29/2026 1:33 PM, Pengyu Luo wrote:
>>>>> On Mon, Jun 29, 2026 at 1:36 PM Mukesh Savaliya
>>>>> <mukesh.savaliya@oss.qualcomm.com> 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.
It may work, but it may fail too. We rather want to decide FIFO/DMA vs 
GSI based on fifo_disabled variable.
>>
>> What's the value of se->base + SE_DMA_IF_EN (+0x2004) on this SE?
> 
> I'm sorry, I read the first sentence only..
> 
> I think the enabling of DMA and the disabling of FIFO are technically
> disjoint operations, but shouldn't be. The programming guide mentions that
> FIFO_DISABLE=1 is set to prevent malicious software from snooping the data
> from the RX FIFO while the SE is operated through the GSI.
> 
> Mukesh, would it make sense to make to rework the checks this way:
> 
No, below actually completely makes things wrong.
Overall it's between GSI vs non GSI [i.e. FIFO/DMA]


fifo_disabled = 1 = GSI [Neither go for FIFO nor for DMA]

fifo_disabled = 0 = non GSI [Then Driver checks data transfer size, if 
<64 prefer FIFO else go for CPU DMA mode]

dma_enabled = 1 [fifo_disabled = 0] = FIFO OR DMA [Driver checks data 
size, if <64 prefer FIFO else go for CPU DMA mode]

let me know if there is still a confusion, we can discuss.

> if (dma_enabled)
> 	prefer GSI, try SE DMA otherwise
> else if (fifo_disabled)
> 	return error, misconfigured SE
> else
> 	fifo mode
> 
> ?
> 
> Konrad