Re: [PATCH] bus: mhi: pci_generic: Increase num of elements in hw event ring

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Fri, Feb 05, 2021 at 09:36:35AM +0100, Loic Poulain wrote:
> We met some sporadic modem crashes during high throughput testing, this
> has been root caused to a lack of elements in the event ring. Indeed,
> the modem is simply crashing when event ring becomes empty.
> 
> It appears that the total number event ring elements is too low given
> the performances of the modem (IPA hardware accelerator). This change
> increases the number of elements in the hardware event ring to 2048,
> which is aligned with what is defined in downstream version:
> https://source.codeaurora.org/quic/la/kernel/msm-4.14/tree/arch/arm64/boot/dts/qcom/sm8150-mhi.dtsi?h=msm-4.14#n482
> 
> With this change, modem coes not crash anymore.
> 
> Note: An event ring element is 16-Byte, so the total memory usage of
> a hardware event ring is now 32KB.
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Thanks,
Mani

> ---
>  drivers/bus/mhi/pci_generic.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/pci_generic.c b/drivers/bus/mhi/pci_generic.c
> index 5b3a23a4..c20f59e 100644
> --- a/drivers/bus/mhi/pci_generic.c
> +++ b/drivers/bus/mhi/pci_generic.c
> @@ -129,7 +129,7 @@ struct mhi_pci_dev_info {
>  
>  #define MHI_EVENT_CONFIG_HW_DATA(ev_ring, ch_num) \
>  	{					\
> -		.num_elements = 256,		\
> +		.num_elements = 2048,		\
>  		.irq_moderation_ms = 1,		\
>  		.irq = (ev_ring) + 1,		\
>  		.priority = 1,			\
> -- 
> 2.7.4
>