linux-kernel - [PATCH v2 2/2] spi: spi-geni-qcom: Add immediate DMA support

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20241128133351.24593-3-quic_jseerapu@quicinc.com>
Date: Thu, 28 Nov 2024 19:03:51 +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 v2 2/2] spi: spi-geni-qcom: 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.

Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
---

v1 -> v2:
   - Moved the spi changes as patch2.

 drivers/spi/spi-geni-qcom.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
index 768d7482102a..53c8f6b7f3c5 100644
--- a/drivers/spi/spi-geni-qcom.c
+++ b/drivers/spi/spi-geni-qcom.c
@@ -472,11 +472,18 @@ static int setup_gsi_xfer(struct spi_transfer *xfer, struct spi_geni_master *mas
 		mas->cur_speed_hz = xfer->speed_hz;
 	}
 
+	/*
+	 * Set QCOM_GPI_IMMEDIATE_DMA flag if transfer length up to 8 bytes.
+	 */
 	if (xfer->tx_buf && xfer->rx_buf) {
 		peripheral.cmd = SPI_DUPLEX;
+		if (xfer->len <= QCOM_GPI_IMMEDIATE_DMA_LEN)
+			peripheral.flags |= QCOM_GPI_IMMEDIATE_DMA;
 	} else if (xfer->tx_buf) {
 		peripheral.cmd = SPI_TX;
 		peripheral.rx_len = 0;
+		if (xfer->len <= QCOM_GPI_IMMEDIATE_DMA_LEN)
+			peripheral.flags |= QCOM_GPI_IMMEDIATE_DMA;
 	} else if (xfer->rx_buf) {
 		peripheral.cmd = SPI_RX;
 		if (!(mas->cur_bits_per_word % MIN_WORD_LEN)) {
-- 
2.17.1