Re: [PATCH v5 03/14] media: iris: Fix VM count passed to firmware

[Vishnu Reddy <busanna.reddy@oss.qualcomm.com>]

On 5/17/2026 10:59 PM, Dmitry Baryshkov wrote:
> On Fri, May 15, 2026 at 04:48:44PM +0530, Vishnu Reddy wrote:
>> On 5/9/2026 12:50 AM, Dmitry Baryshkov wrote:
>>> On Sat, May 09, 2026 at 12:29:52AM +0530, Vishnu Reddy wrote:
>>>> On Glymur, firmware interprets the value written to CPU_CS_SCIACMDARG3 as
>>>> the number of virtual machines (VMs) and internally adds 1 to it. Writing
>>>> 1 causes firmware to treat it as 2 VMs. Since only one VM is required,
>>>> remove this write to leave the register at its reset value of 0. This does
>>>> not affect other platforms as only Glymur firmware uses this register,
>>>> earlier platform firmwares ignore it.
>>> The explanation is pretty suspicious. I can see this write in venus
>>> sources too and it was added in the initial submission, dating 2017. The
>>> driver targeted two platforms, MSM8916 and MSM8996, so this write
>>> predates Glymur pretty much.
>> Thank you for the historical context! I checked with the firmware team and
>> confirmed that this register is not read by any of the platform firmwares
>> currently supported in the Iris driver. Regarding MSM8916 and MSM8996, those
>> are not supported in the Iris driver.
> So, which platforms actually needed that register? The "currently
> supported" is not strong enough. We are bringing in Agatti support and
> support for SM8150 and SDM845 is in discussion. I would not be surprised
> if we end up porting other older platforms too. So, you are changing the
> historical behaviour. You need to document the applicability of the
> change.

Apologies for the late reply, I was on vacation last week.

I'll move this to a glymur-specific vpu_ops hook and keep the existing behavior
for the remaining platforms.

>>>> Fixes: abf5bac63f68 ("media: iris: implement the boot sequence of the firmware")
>>>> Cc: stable@vger.kernel.org
>>>> Reviewed-by: Vikash Garodia <vikash.garodia@oss.qualcomm.com>
>>>> Signed-off-by: Vishnu Reddy <busanna.reddy@oss.qualcomm.com>
>>>> ---
>>>>  drivers/media/platform/qcom/iris/iris_vpu_common.c | 1 -
>>>>  1 file changed, 1 deletion(-)
>>>>