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Fri, 15 May 2026 10:41:17 -0700 (PDT) From: Sanjay Chitroda X-Google-Original-From: Sanjay Chitroda To: jic23@kernel.org Cc: dlechner@baylibre.com, nuno.sa@analog.com, andy@kernel.org, sanjayembeddedse@gmail.com, tglx@kernel.org, christophe.jaillet@wanadoo.fr, mingo@kernel.org, kees@kernel.org, nabijaczleweli@nabijaczleweli.xyz, kyungmin.park@samsung.com, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v8 12/12] iio: ssp_sensors: reuse embedded RX buffer for SPI transfers Date: Fri, 15 May 2026 23:10:17 +0530 Message-Id: <20260515174017.3962168-13-sanjayembedded@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260515174017.3962168-1-sanjayembedded@gmail.com> References: <20260515174017.3962168-1-sanjayembedded@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Sanjay Chitroda Avoid allocating a temporary DMA buffer in the interrupt context when handling hub-to-AP and AP-to-hub SPI write messages. Replace the dynamically allocated RX buffer with a fixed-size, preallocated buffer embedded in the driver structure and reused for all SPI receive operations. This removes memory allocation from the IRQ path, simplifies lifetime management. Signed-off-by: Sanjay Chitroda --- Changes in v6: - Address review comment of Jonathan and use __aligned(IIO_DMA_MINALIGN) and have buffer assignment specific to block instead of top. - Regarding DMA and size discussion point are open to check - v7 change: https://lore.kernel.org/all/20260426091710.3722035-10-sanjayembedded@gmail.com/ Changes in v6: - Replace dynamically allocated RX buffer with embedded fixed-size buffer - Fix struct layout to satisfy DMA alignment constraints comment from David - v5 change: https://lore.kernel.org/all/20260406080852.2727453-6-sanjayembedded@gmail.com/ Changes in v5: - Rebase change on top of latest v5 patch series. Changes in v4: - Use preallocated buffer and stash a buffer that gets reused each time instead of a fresh allocation. - v3 change: https://lore.kernel.org/all/20260315125509.857195-3-sanjayembedded@gmail.com/ Changes in v3: - prepare series to have all respective cleanup API support for the ssp_sensors following input from Andy Shevchenko - v2 change: https://lore.kernel.org/all/20260311174151.3441429-1-sanjayembedded@gmail.com/ Changes in v2: - split series to individual patch - address review comment from Andy Shevchenko - v1 change: https://lore.kernel.org/all/20260310200513.2162018-3-sanjayembedded@gmail.com/ --- drivers/iio/common/ssp_sensors/ssp.h | 3 +++ drivers/iio/common/ssp_sensors/ssp_spi.c | 17 +++-------------- 2 files changed, 6 insertions(+), 14 deletions(-) diff --git a/drivers/iio/common/ssp_sensors/ssp.h b/drivers/iio/common/ssp_sensors/ssp.h index f649cdecc277..6d7409db014e 100644 --- a/drivers/iio/common/ssp_sensors/ssp.h +++ b/drivers/iio/common/ssp_sensors/ssp.h @@ -174,6 +174,7 @@ struct ssp_sensorhub_info { * @pending_list: pending list for messages queued to be sent/read * @sensor_devs: registered IIO devices table * @enable_refcount: enable reference count for wdt (watchdog timer) + * @rx_buf: buffer to receive SPI data * @header_buffer: cache aligned buffer for packet header */ struct ssp_data { @@ -221,6 +222,8 @@ struct ssp_data { struct iio_dev *sensor_devs[SSP_SENSOR_MAX]; atomic_t enable_refcount; + u8 rx_buf[SSP_DATA_PACKET_SIZE] __aligned(IIO_DMA_MINALIGN); + __le16 header_buffer[SSP_HEADER_BUFFER_SIZE / sizeof(__le16)] __aligned(IIO_DMA_MINALIGN); }; diff --git a/drivers/iio/common/ssp_sensors/ssp_spi.c b/drivers/iio/common/ssp_sensors/ssp_spi.c index 172b4bbd298c..d6919e86aa95 100644 --- a/drivers/iio/common/ssp_sensors/ssp_spi.c +++ b/drivers/iio/common/ssp_sensors/ssp_spi.c @@ -396,17 +396,13 @@ int ssp_irq_msg(struct ssp_data *data) * but the slave should not send such ones - it is to * check but let's handle this */ - buffer = kmalloc(length, GFP_KERNEL | GFP_DMA); - if (!buffer) - return -ENOMEM; + buffer = data->rx_buf; /* got dead packet so it is always an error */ ret = spi_read(data->spi, buffer, length); if (ret >= 0) ret = -EPROTO; - kfree(buffer); - dev_err(SSP_DEV, "No match error %x\n", msg_options); @@ -438,22 +434,15 @@ int ssp_irq_msg(struct ssp_data *data) return ret; } case SSP_HUB2AP_WRITE: - buffer = kzalloc(length, GFP_KERNEL | GFP_DMA); - if (!buffer) - return -ENOMEM; + buffer = data->rx_buf; ret = spi_read(data->spi, buffer, length); if (ret < 0) { dev_err(SSP_DEV, "spi read fail\n"); - kfree(buffer); return ret; } - ret = ssp_parse_dataframe(data, buffer, length); - - kfree(buffer); - return ret; - + return ssp_parse_dataframe(data, buffer, length); default: dev_err(SSP_DEV, "unknown msg type\n"); return -EPROTO; -- 2.34.1