linux-kernel - Re: [PATCH v5 2/4] dmaengine: gpi: Add Lock and Unlock TRE support to access I2C exclusively

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <5ef44277-6739-4e1e-af62-0f40ae081ec1@quicinc.com>
Date: Wed, 18 Dec 2024 18:04:04 +0530
From: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
To: Vinod Koul <vkoul@...nel.org>
CC: <konrad.dybcio@...aro.org>, <andersson@...nel.org>,
        <andi.shyti@...nel.org>, <linux-arm-msm@...r.kernel.org>,
        <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-i2c@...r.kernel.org>, <conor+dt@...nel.org>,
        <agross@...nel.org>, <devicetree@...r.kernel.org>, <linux@...blig.org>,
        <dan.carpenter@...aro.org>, <Frank.Li@....com>,
        <konradybcio@...nel.org>, <bryan.odonoghue@...aro.org>,
        <krzk+dt@...nel.org>, <robh@...nel.org>, <quic_vdadhani@...cinc.com>
Subject: Re: [PATCH v5 2/4] dmaengine: gpi: Add Lock and Unlock TRE support to
 access I2C exclusively

Hi Vinod, Thanks !  I just saw your comments now as somehow it was going 
in some other folder and didn't realize.

On 12/4/2024 5:51 PM, Vinod Koul wrote:
> On 02-12-24, 16:13, Mukesh Kumar Savaliya wrote:
>> Thanks for the review comments Vinod !
>>
>> On 12/2/2024 12:17 PM, Vinod Koul wrote:
>>> On 29-11-24, 20:13, Mukesh Kumar Savaliya wrote:
>>>> GSI DMA provides specific TREs(Transfer ring element) namely Lock and
>>>> Unlock TRE. It provides mutually exclusive access to I2C controller from
>>>> any of the processor(Apps,ADSP). Lock prevents other subsystems from
>>>> concurrently performing DMA transfers and avoids disturbance to data path.
>>>> Basically for shared I2C usecase, lock the SE(Serial Engine) for one of
>>>> the processor, complete the transfer, unlock the SE.
>>>>
>>>> Apply Lock TRE for the first transfer of shared SE and Apply Unlock
>>>> TRE for the last transfer.
>>>>
>>>> Also change MAX_TRE macro to 5 from 3 because of the two additional TREs.
>>>>
>>>
>>> ...
>>>
>>>> @@ -65,6 +65,9 @@ enum i2c_op {
>>>>     * @rx_len: receive length for buffer
>>>>     * @op: i2c cmd
>>>>     * @muli-msg: is part of multi i2c r-w msgs
>>>> + * @shared_se: bus is shared between subsystems
>>>> + * @bool first_msg: use it for tracking multimessage xfer
>>>> + * @bool last_msg: use it for tracking multimessage xfer
>>>>     */
>>>>    struct gpi_i2c_config {
>>>>    	u8 set_config;
>>>> @@ -78,6 +81,9 @@ struct gpi_i2c_config {
>>>>    	u32 rx_len;
>>>>    	enum i2c_op op;
>>>>    	bool multi_msg;
>>>> +	bool shared_se;
>>>
>>> Looking at this why do you need this field? It can be internal to your
>>> i2c driver... Why not just set an enum for lock and use the values as
>>> lock/unlock/dont care and make the interface simpler. I see no reason to
>>> use three variables to communicate the info which can be handled in
>>> simpler way..?
>>>
>> Below was earlier reply to [PATCH V3, 2/4], please let me know if you have
>> any additional comment and need further clarifications.
> 
> Looks like you misunderstood, the question is why do you need three
> variables to convey this info..? Use a single variable please
Yes, I think so. Please let me clarify.
First variable is a feature flag and it's required to be explicitly 
mentioned by client (i2c/spi/etc) to GSI driver.

Second and third, can be optimized to boolean so either first or last 
can be passed.

Please correct me or add simple change where you would like to make, i 
can add that.
> 
>> --
>>> Looking at the usage in following patches, why cant this be handled
>>> internally as part of prep call?
>>>
>> As per design, i2c driver iterates over each message and submits to GPI
>> where it creates TRE. Since it's per transfer, we need to create Lock and
>> Unlock TRE based on first or last message.
>> --
>>>> +	bool first_msg;
>>>> +	bool last_msg;
>>>
>