linux-kernel - Re: [PATCH] soc: qcom: geni-se: Do not bother about enable/disable of interrupts in secondary sequencer for non-uart modes

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Message-ID: <39b5a025-d678-57d4-9e97-432ee1763186@quicinc.com>
Date:   Tue, 13 Jun 2023 23:54:31 +0530
From:   Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
To:     Doug Anderson <dianders@...omium.org>
CC:     <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_msavaliy@...cinc.com>,
        <mka@...omium.org>, <swboyd@...omium.org>,
        <quic_vtanuku@...cinc.com>
Subject: Re: [PATCH] soc: qcom: geni-se: Do not bother about enable/disable of
 interrupts in secondary sequencer for non-uart modes

Hi,


On 6/13/2023 11:27 PM, Doug Anderson wrote:
> Hi,
>
> On Tue, Jun 13, 2023 at 9:07 AM Vijaya Krishna Nivarthi
> <quic_vnivarth@...cinc.com> wrote:
>> Hi,
>>
>>
>> On 6/12/2023 7:09 PM, Vijaya Krishna Nivarthi wrote:
>>> Hi,
>>>
>>> Thank you very much for the review...
>>>
>>>
>>> On 6/7/2023 9:41 PM, Doug Anderson wrote:
>>>> Hi,
>>>>
>>>> On Fri, Jun 2, 2023 at 11:13 AM Vijaya Krishna Nivarthi
>>>> <quic_vnivarth@...cinc.com> wrote:
>>>>> The select_fifo/dma_mode() functions in geni driver enable/disable
>>>>> interrupts (secondary included) conditionally for non-uart modes, while
>>>>> uart is supposed to manage this internally.
>>>>> However, only uart uses secondary IRQs while spi, i2c do not care about
>>>>> these at all making their enablement (or disablement) totally
>>>>> unnecessary
>>>>> for these protos.
>>>>>
>>>>> Drop enabling/disabling secondary IRQs for non-uart modes.
>>>>> This doesn't solve any observed problem but only gets rid of code
>>>>> pieces
>>>>> that are not required.
>>>>>
>>>>> Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
>>>>> ---
>>>>>    drivers/soc/qcom/qcom-geni-se.c | 24 ++++--------------------
>>>>>    1 file changed, 4 insertions(+), 20 deletions(-)
>>>> This seems like a nice cleanup to me. It's still odd that the general
>>>> code has a special case for UART, but I guess the alternative is to
>>>> duplicate the exact same logic for both the i2c and SPI drivers. I
>>>> won't insist on that, though I wouldn't be opposed to it either.
>>>>
>>>> I guess one comment, though: should we also remove the code that
>>>> messes with "SE_GENI_S_IRQ_EN" in geni_se_select_gpi_mode()?
>>>
>>> Right now we have gpi-dma mode support for i2c and spi but not for uart.
>>>
>>> Even when gpi-dma support is added, uart driver's interrupt handler
>>> would not be invoked so I believe it would be safe to drop that code
>>> from geni_se_select_gpi_mode() too.
>>>
>>> I will post v2 dropping same after some more lookup.
>>
>> Looking at this once again, I am more inclined towards leaving alone
>> gpi_mode() for now.
>>
>> It probably needs cleanup but we want to take that up at a later time.
>>
>> Meanwhile its not causing much harm as we don't switch modes dynamically
>> for gpi case, so we are not losing much time there reading from and
>> writing to registers.
>>
>> Please let know your thoughts.
> It's not really about the time needed for the extra register writes,
> but just someone trying to understand the code who might be trying to
> figure out what bits are relevant. The bits related to the secondary
> sequencer's interrupts don't do anything useful when we're using the
> controller for i2c/spi, so why not delete them?


Agreed the s_irqs are not useful for spi/i2c but Right now I am not 
really sure how uart + gsi mode is going to look like.

So how about we move the part that messes with s_irq in gpi_mode() into 
a *if(proto == GENI_SE_UART)* conditional?

Understand we are adding to weirdness but Would that be ok for now?


thank you,

Vijay/


>
> -Doug