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

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

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.
> 
> 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:

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

?

Konrad