linux-kernel - [PATCH v1 0/1] Add immediate DMA support

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Message-ID: <20241121115201.2191-1-quic_jseerapu@quicinc.com>
Date: Thu, 21 Nov 2024 17:22:00 +0530
From: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
To: Vinod Koul <vkoul@...nel.org>, Mark Brown <broonie@...nel.org>
CC: <linux-arm-msm@...r.kernel.org>, <dmaengine@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-spi@...r.kernel.org>,
        <quic_msavaliy@...cinc.com>, <quic_vtanuku@...cinc.com>
Subject: [PATCH v1 0/1] Add immediate DMA support

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.

Jyothi Kumar Seerapu (1):
  spi: spi-geni-qcom: Add immediate DMA support

 drivers/dma/qcom/gpi.c           | 32 +++++++++++++++++++++++++++-----
 drivers/spi/spi-geni-qcom.c      |  7 +++++++
 include/linux/dma/qcom-gpi-dma.h |  7 +++++++
 3 files changed, 41 insertions(+), 5 deletions(-)

-- 
2.17.1