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[98.183.112.25]) by smtp.gmail.com with ESMTPSA id d28-20020a056830045c00b006dc0802ddf5sm52466otc.5.2024.01.25.15.47.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Jan 2024 15:47:59 -0800 (PST) From: David Lechner To: Mark Brown Cc: David Lechner , linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] spi: avoid double validation in __spi_sync() Date: Thu, 25 Jan 2024 17:47:31 -0600 Message-ID: <20240125234732.3530278-2-dlechner@baylibre.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-spi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 The __spi_sync() function calls __spi_validate() early in the function. Later, it can call spi_async_locked() which calls __spi_validate() again. __spi_validate() is an expensive function, so we can improve performance measurably by avoiding calling it twice. Instead of calling spi_async_locked(), we can call __spi_async() with the spin lock held. spi_async_locked() is removed since there are no more callers. Signed-off-by: David Lechner --- I tested this using an ADC driver that does a lot of spi_sync() calls to read samples. I disabled the no-queue fast path by setting ctlr->must_async so that the modified code always runs. With this change I was able to increase the sample rate of the ADC about 6% from 14.5 kHz to 15.4 kHz. drivers/spi/spi.c | 58 +++++------------------------------------------ 1 file changed, 6 insertions(+), 52 deletions(-) diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 7a70ef47cdf6..6610aeced765 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -4278,57 +4278,6 @@ int spi_async(struct spi_device *spi, struct spi_message *message) } EXPORT_SYMBOL_GPL(spi_async); -/** - * spi_async_locked - version of spi_async with exclusive bus usage - * @spi: device with which data will be exchanged - * @message: describes the data transfers, including completion callback - * Context: any (IRQs may be blocked, etc) - * - * This call may be used in_irq and other contexts which can't sleep, - * as well as from task contexts which can sleep. - * - * The completion callback is invoked in a context which can't sleep. - * Before that invocation, the value of message->status is undefined. - * When the callback is issued, message->status holds either zero (to - * indicate complete success) or a negative error code. After that - * callback returns, the driver which issued the transfer request may - * deallocate the associated memory; it's no longer in use by any SPI - * core or controller driver code. - * - * Note that although all messages to a spi_device are handled in - * FIFO order, messages may go to different devices in other orders. - * Some device might be higher priority, or have various "hard" access - * time requirements, for example. - * - * On detection of any fault during the transfer, processing of - * the entire message is aborted, and the device is deselected. - * Until returning from the associated message completion callback, - * no other spi_message queued to that device will be processed. - * (This rule applies equally to all the synchronous transfer calls, - * which are wrappers around this core asynchronous primitive.) - * - * Return: zero on success, else a negative error code. - */ -static int spi_async_locked(struct spi_device *spi, struct spi_message *message) -{ - struct spi_controller *ctlr = spi->controller; - int ret; - unsigned long flags; - - ret = __spi_validate(spi, message); - if (ret != 0) - return ret; - - spin_lock_irqsave(&ctlr->bus_lock_spinlock, flags); - - ret = __spi_async(spi, message); - - spin_unlock_irqrestore(&ctlr->bus_lock_spinlock, flags); - - return ret; - -} - static void __spi_transfer_message_noqueue(struct spi_controller *ctlr, struct spi_message *msg) { bool was_busy; @@ -4376,6 +4325,7 @@ static void spi_complete(void *arg) static int __spi_sync(struct spi_device *spi, struct spi_message *message) { DECLARE_COMPLETION_ONSTACK(done); + unsigned long flags; int status; struct spi_controller *ctlr = spi->controller; @@ -4419,7 +4369,11 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message) */ message->complete = spi_complete; message->context = &done; - status = spi_async_locked(spi, message); + + spin_lock_irqsave(&ctlr->bus_lock_spinlock, flags); + status = __spi_async(spi, message); + spin_unlock_irqrestore(&ctlr->bus_lock_spinlock, flags); + if (status == 0) { wait_for_completion(&done); status = message->status;