linux-kernel - Re: [PATCH] fpga: altera-cvp: Truncated bitstream error support

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Date:   Thu, 19 May 2022 17:39:07 +0800
From:   tien.sung.ang@...el.com
To:     mdf@...nel.org, hao.wu@...el.com, yilun.xu@...el.com,
        trix@...hat.com
Cc:     linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org,
        tien.sung.ang@...el.com
Subject: Re: [PATCH] fpga: altera-cvp: Truncated bitstream error support

Thanks for bringing this up. Yes, you are right that the fpga_mgr sees this
as an error irrespective of the value. The CvP driver is changed now to just
indicate the correct error which recommends a retry. To me understanding,
EAGAIN was this. The fpga manager now looks like is going to return a CvP
failure in short. 
A BUSY state does not seem to be able to solve this issue. 
Even an extended time-out didn't resolve this error state. The current time-out
is set to 10seconds.   
However, the main objective is to also handle the error if the CvP firmware
is not responsive. The error_path flow is to reset the CVP mode and HIP_CLK_SEL bit
as recommended by the firmware engineers. 
The flow prescribed here is also an identical copy of working CvP driver 
which is also owned by Intel. This driver is a downstream driver which is 
not part of the Linux kernel. We are now porting this differences over to 
the current upstream CvP driver.