linux-kernel - Re: [PATCH v5] dmaengine: qcom: gpi: Add GPI immediate DMA support for SPI protocol

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

Message-ID: <4nazbhr2gqgvxomy5ewewnrvivppof3yxo3yebkhkfvfls25pm@kfkvizxg4cqy>
Date: Mon, 9 Dec 2024 12:36:32 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
Cc: Vinod Koul <vkoul@...nel.org>, linux-arm-msm@...r.kernel.org, 
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org, quic_msavaliy@...cinc.com, 
	quic_vtanuku@...cinc.com
Subject: Re: [PATCH v5] dmaengine: qcom: gpi: Add GPI immediate DMA support
 for SPI protocol

On Mon, Dec 09, 2024 at 01:20:33PM +0530, Jyothi Kumar Seerapu wrote:
> The DMA TRE(Transfer ring element) buffer contains the DMA
> buffer address. Accessing data from this address can cause
> significant delays in SPI transfers, which can be mitigated to
> some extent by utilizing immediate DMA support.
> 
> QCOM GPI DMA hardware supports an immediate DMA feature for data
> up to 8 bytes, storing the data directly in the DMA TRE buffer
> instead of the DMA buffer address. This enhancement enables faster
> SPI data transfers.
> 
> This optimization reduces the average transfer time from 25 us to
> 16 us for a single SPI transfer of 8 bytes length, with a clock
> frequency of 50 MHz.
> 
> Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
> ---
> v4 -> v5:
>    - For Immediate DMA, instead of making dma type as 0x10 and then
>      enable 16th bit of dword3, directly updating the dma type as 0x11.
> 
>    Link to v4:
> 	https://lore.kernel.org/all/20241205170611.18566-1-quic_jseerapu@quicinc.com/  
> 
> v3 -> v4:
>    - Instead using extra variable(immediate_dma) for Immediate dma
>      condition check, made it to inlined.
>    - Removed the extra brackets around Immediate dma condition check.
> 
>    Link to v3:
>         https://lore.kernel.org/lkml/20241204122059.24239-1-quic_jseerapu@quicinc.com/
> 
> v2 -> v3:
>    - When to enable Immediate DMA support, control is moved to GPI driver
>      from SPI driver.
>    - Optimizations are done in GPI driver related to immediate dma changes.
>    - Removed the immediate dma supported changes in qcom-gpi-dma.h file
>      and handled in GPI driver.
> 
>    Link to v2:
>         https://lore.kernel.org/all/20241128133351.24593-2-quic_jseerapu@quicinc.com/
>         https://lore.kernel.org/all/20241128133351.24593-3-quic_jseerapu@quicinc.com/
> 
> v1 -> v2:
>    - Separated the patches to dmaengine and spi subsystems
>    - Removed the changes which are not required for this feature from
>      qcom-gpi-dma.h file.
>    - Removed the type conversions used in gpi_create_spi_tre.
> 
>    Link to v1:
>         https://lore.kernel.org/lkml/20241121115201.2191-2-quic_jseerapu@quicinc.com/
> 
>  drivers/dma/qcom/gpi.c | 31 +++++++++++++++++++++++++------
>  1 file changed, 25 insertions(+), 6 deletions(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

-- 
With best wishes
Dmitry