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Tue, 14 Apr 2026 22:08:24 -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, nabijaczleweli@nabijaczleweli.xyz, kees@kernel.org, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v6 7/7] iio: ssp_sensors: reuse embedded RX buffer for SPI transfers Date: Wed, 15 Apr 2026 10:37:49 +0530 Message-Id: <20260415050749.3858046-8-sanjayembedded@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260415050749.3858046-1-sanjayembedded@gmail.com> References: <20260415050749.3858046-1-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. No functional change intended. Signed-off-by: Sanjay Chitroda --- Changes in v6: - Replace dynamically allocated RX buffer with embedded fixed-size buffer - Fix struct layout to satisfy DMA alignment constraints comment from David - Link to v5: https://lore.kernel.org/all/20260406080852.2727453-1-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. - Link to v3: 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 - Link to v2 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 - Link to v1 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 | 20 ++------------------ 2 files changed, 5 insertions(+), 18 deletions(-) diff --git a/drivers/iio/common/ssp_sensors/ssp.h b/drivers/iio/common/ssp_sensors/ssp.h index f649cdecc277..8295bb7062a3 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]; + __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 92418721ff82..bab84b25edff 100644 --- a/drivers/iio/common/ssp_sensors/ssp_spi.c +++ b/drivers/iio/common/ssp_sensors/ssp_spi.c @@ -336,7 +336,7 @@ static int ssp_parse_dataframe(struct ssp_data *data, char *dataframe, int len) /* threaded irq */ int ssp_irq_msg(struct ssp_data *data) { - char *buffer; + char *buffer = data->rx_buf; u8 msg_type; int ret; u16 length, msg_options; @@ -380,19 +380,12 @@ 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) { - ret = -ENOMEM; - goto _unlock; - } /* 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); @@ -425,22 +418,13 @@ int ssp_irq_msg(struct ssp_data *data) mutex_unlock(&data->pending_lock); break; case SSP_HUB2AP_WRITE: - buffer = kzalloc(length, GFP_KERNEL | GFP_DMA); - if (!buffer) - return -ENOMEM; - ret = spi_read(data->spi, buffer, length); if (ret < 0) { dev_err(SSP_DEV, "spi read fail\n"); - kfree(buffer); break; } - ret = ssp_parse_dataframe(data, buffer, length); - - kfree(buffer); - break; - + return ssp_parse_dataframe(data, buffer, length); default: dev_err(SSP_DEV, "unknown msg type\n"); return -EPROTO; -- 2.34.1