linux-kernel - Re: [PATCH 2/4] gpu: host1x: Enable gather filter

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Date:   Sun, 20 Aug 2017 19:44:43 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Mikko Perttunen <mperttunen@...dia.com>, thierry.reding@...il.com,
        jonathanh@...dia.com
Cc:     dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] gpu: host1x: Enable gather filter

On 20.08.2017 19:24, Dmitry Osipenko wrote:
> On 18.08.2017 19:15, Mikko Perttunen wrote:
>> The gather filter is a feature present on Tegra124 and newer where the
>> hardware prevents GATHERed command buffers from executing commands
>> normally reserved for the CDMA pushbuffer which is maintained by the
>> kernel driver.
>>
>> This commit enables the gather filter on all supporting hardware.
>>
>> Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
>> ---
>>  drivers/gpu/host1x/hw/channel_hw.c          | 22 ++++++++++++++++++++++
>>  drivers/gpu/host1x/hw/hw_host1x04_channel.h | 12 ++++++++++++
>>  drivers/gpu/host1x/hw/hw_host1x05_channel.h | 12 ++++++++++++
>>  3 files changed, 46 insertions(+)
>>
>> diff --git a/drivers/gpu/host1x/hw/channel_hw.c b/drivers/gpu/host1x/hw/channel_hw.c
>> index 0161da331702..5c0dc6bb51d1 100644
>> --- a/drivers/gpu/host1x/hw/channel_hw.c
>> +++ b/drivers/gpu/host1x/hw/channel_hw.c
>> @@ -181,10 +181,32 @@ static int channel_submit(struct host1x_job *job)
>>  	return err;
>>  }
>>  
>> +static void enable_gather_filter(struct host1x *host,
>> +				 struct host1x_channel *ch)
>> +{
>> +#if HOST1X_HW >= 6
>> +	u32 val;
>> +
>> +	if (!host->hv_regs)
>> +		return;
> 
> Is it really possible that gather filter could be not present on HW without
> hypervisor? Maybe there is other way to enable it in that case?
> 
> Is possible at all that hypervisor could be missed?

BTW, this is also incoherent with the 'syncpoint protection' patch which doesn't
check for hypervisor presence.

-- 
Dmitry