linux-kernel - Re: [PATCH net 1/2] net: ipa: only clear hardware state if setup has completed

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Date:   Fri, 9 Oct 2020 14:39:45 -0500
From:   Alex Elder <elder@...aro.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     davem@...emloft.net, evgreen@...omium.org, subashab@...eaurora.org,
        cpratapa@...eaurora.org, bjorn.andersson@...aro.org,
        mka@...omium.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/2] net: ipa: only clear hardware state if setup has
 completed

On 10/9/20 2:25 PM, Jakub Kicinski wrote:
> On Tue,  6 Oct 2020 16:30:46 -0500 Alex Elder wrote:
>> In the setup phase of initialization, GSI firmware gets loaded
>> and initialized, and the AP command TX and default RX endpoints
>> get set up.  Until that happens, IPA commands must not be issued
>> to the hardware.
>>
>> If the modem crashes, we stop endpoint channels and perform a
>> number of other activities to clear modem-related IPA state,
>> including zeroing filter and routing tables (using IPA commands).
>> This is a bug if setup is not complete.  We should also not be
>> performing the other cleanup activity in that case either.
>>
>> Fix this by returning immediately when handling a modem crash if we
>> haven't completed setup.
>>
>> Fixes: a646d6ec9098 ("soc: qcom: ipa: modem and microcontroller")
>> Tested-by: Matthias Kaehlcke <mka@...omium.org>
>> Signed-off-by: Alex Elder <elder@...aro.org>
> 
>> diff --git a/drivers/net/ipa/ipa_modem.c b/drivers/net/ipa/ipa_modem.c
>> index e34fe2d77324e..dd5b89c5cb2d4 100644
>> --- a/drivers/net/ipa/ipa_modem.c
>> +++ b/drivers/net/ipa/ipa_modem.c
>> @@ -285,6 +285,9 @@ static void ipa_modem_crashed(struct ipa *ipa)
>>   	struct device *dev = &ipa->pdev->dev;
>>   	int ret;
>>   
>> +	if (!ipa->setup_complete)
>> +		return;
>> +
>>   	ipa_endpoint_modem_pause_all(ipa, true);
>>   
>>   	ipa_endpoint_modem_hol_block_clear_all(ipa);
> 
> The only call site already checks setup_complete, so this is not needed,
> no?

Wow, you are correct.

I was mainly focused on the fact that the ipa_modem_crashed()
call could happen asynchronously, and that it called
ipa_table_reset() which requires IPA immediate commands.
I should have followed it back to its callers.

I agree with you, this is not needed.  The other patch
is definitely needed though.

Would you like me to re-post that single patch, or is
it acceptable as-is?

Thank you for reviewing this and catching my mistake.

					-Alex

> $ git grep -C2 ipa_modem_crashed\(
> drivers/net/ipa/ipa_modem.c-
> drivers/net/ipa/ipa_modem.c-/* Treat a "clean" modem stop the same as a crash */
> drivers/net/ipa/ipa_modem.c:static void ipa_modem_crashed(struct ipa *ipa)
> drivers/net/ipa/ipa_modem.c-{
> drivers/net/ipa/ipa_modem.c-    struct device *dev = &ipa->pdev->dev;
> --
> drivers/net/ipa/ipa_modem.c-                     notify_data->crashed ? "crashed" : "stopping");
> drivers/net/ipa/ipa_modem.c-            if (ipa->setup_complete)
> drivers/net/ipa/ipa_modem.c:                    ipa_modem_crashed(ipa);
> drivers/net/ipa/ipa_modem.c-            break;
> drivers/net/ipa/ipa_modem.c-
>