linux-kernel - Re: [PATCH v2 1/5] media: venus: add a routine to reset ARM9

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Date:   Wed, 04 Jul 2018 14:05:30 +0530
From:   Vikash Garodia <vgarodia@...eaurora.org>
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>
Cc:     hverkuil@...all.nl, mchehab@...nel.org, robh@...nel.org,
        mark.rutland@....com, andy.gross@...aro.org,
        bjorn.andersson@...aro.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-soc@...r.kernel.org, devicetree@...r.kernel.org,
        acourbot@...omium.org, linux-media-owner@...r.kernel.org
Subject: Re: [PATCH v2 1/5] media: venus: add a routine to reset ARM9

Hi Stanimir,

Thanks for the review.

On 2018-06-02 03:45, Stanimir Varbanov wrote:
> Hi Vikash,
> 
> On  1.06.2018 23:26, Vikash Garodia wrote:
>> Add a new routine to reset the ARM9 and brings it
>> out of reset. This is in preparation to add PIL
>> functionality in venus driver.
> 
> please squash this patch with 4/5. I don't see a reason to add a
> function which is not used. Shouldn't this produce gcc warnings?

Will squash the api definition with the patch using it.

>> 
>> Signed-off-by: Vikash Garodia <vgarodia@...eaurora.org>
>> ---
>>   drivers/media/platform/qcom/venus/firmware.c     | 26 
>> ++++++++++++++++++++++++
>>   drivers/media/platform/qcom/venus/hfi_venus_io.h |  5 +++++
>>   2 files changed, 31 insertions(+)
>> 
>> diff --git a/drivers/media/platform/qcom/venus/firmware.c 
>> b/drivers/media/platform/qcom/venus/firmware.c
>> index 521d4b3..7d89b5a 100644
>> --- a/drivers/media/platform/qcom/venus/firmware.c
>> +++ b/drivers/media/platform/qcom/venus/firmware.c
>> @@ -14,6 +14,7 @@
>>     #include <linux/device.h>
>>   #include <linux/firmware.h>
>> +#include <linux/delay.h>
>>   #include <linux/kernel.h>
>>   #include <linux/io.h>
>>   #include <linux/of.h>
>> @@ -22,11 +23,36 @@
>>   #include <linux/sizes.h>
>>   #include <linux/soc/qcom/mdt_loader.h>
>>   +#include "core.h"
>>   #include "firmware.h"
>> +#include "hfi_venus_io.h"
>>     #define VENUS_PAS_ID			9
>>   #define VENUS_FW_MEM_SIZE		(6 * SZ_1M)
>>   +static void venus_reset_hw(struct venus_core *core)
> 
> can we rename this to venus_reset_cpu? reset_hw sounds like we reset
> vcodec IPs, so I think we can be more exact here.
> 
>> +{
>> +	void __iomem *reg_base = core->base;
> 
> just 'base', please.
Ok.

>> +
>> +	writel(0, reg_base + WRAPPER_FW_START_ADDR);
>> +	writel(VENUS_FW_MEM_SIZE, reg_base + WRAPPER_FW_END_ADDR);
>> +	writel(0, reg_base + WRAPPER_CPA_START_ADDR);
>> +	writel(VENUS_FW_MEM_SIZE, reg_base + WRAPPER_CPA_END_ADDR);
>> +	writel(0x0, reg_base + WRAPPER_CPU_CGC_DIS);
>> +	writel(0x0, reg_base + WRAPPER_CPU_CLOCK_CONFIG);
>> +
>> +	/* Make sure all register writes are committed. */
>> +	mb();
> 
> the comment says "register writes" hence shouldn't this be wmb? Also
> if we are going to have explicit memory barrier why not use
> writel_relaxed?
>> +
>> +	/*
>> +	 * Need to wait 10 cycles of internal clocks before bringing ARM9
> 
> Do we know what is the minimum frequency of the internal ARM9 clocks?
> I.e does 1us is enough for all venus versions.

ARM9 is yet not brought out of reset at this point. Sleep might be added
to ensure that the register writes are completed. But as Bjorn 
commented,
only way to ensure registers are written is to read them back. I do not 
have
proper justification of sleep as this code was used for many chipset 
bringup.
I can try by removing the sleep and if goes well, we can live without 
it.

>> +	 * out of reset.
>> +	 */
>> +	udelay(1);
>> +
>> +	/* Bring Arm9 out of reset */
> 
> ARM9
> 
>> +	writel_relaxed(0, reg_base + WRAPPER_A9SS_SW_RESET);
> 
> in my opinion we should have a wmb here too
I guess if sleep is removed, we will be left with only the above 
instruction.
so no need to ensure the access order.

> regards,
> Stan