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

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Message-ID: <Z01YBLcxDXI2UwXR@vaman>
Date: Mon, 2 Dec 2024 12:17:32 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
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

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..?

> +	bool first_msg;
> +	bool last_msg;

-- 
~Vinod