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Wed, 25 Jun 2025 02:56:26 -0700 (PDT) Message-ID: Date: Wed, 25 Jun 2025 10:56:25 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/6] spi: spi-fsl-dspi: Store status directly in cur_msg->status To: Frank Li Cc: Vladimir Oltean , Mark Brown , Vladimir Oltean , Arnd Bergmann , Larisa Grigore , Christoph Hellwig , linux-spi@vger.kernel.org, imx@lists.linux.dev, linux-kernel@vger.kernel.org References: <20250624-james-nxp-spi-dma-v3-0-e7d574f5f62c@linaro.org> <20250624-james-nxp-spi-dma-v3-2-e7d574f5f62c@linaro.org> Content-Language: en-US From: James Clark In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 24/06/2025 5:18 pm, Frank Li wrote: > On Tue, Jun 24, 2025 at 11:35:32AM +0100, James Clark wrote: >> This will allow us to return a status from the interrupt handler in a >> later commit and avoids copying it at the end of >> dspi_transfer_one_message(). For consistency make polling and DMA modes >> use the same mechanism. >> >> Refactor dspi_rxtx() and dspi_poll() to not return -EINPROGRESS because >> this isn't actually a status that was ever returned to the core layer >> but some internal state. Wherever that was used we can look at dspi->len >> instead. >> >> No functional changes intended. >> >> Signed-off-by: James Clark >> --- >> drivers/spi/spi-fsl-dspi.c | 68 ++++++++++++++++++++++++---------------------- >> 1 file changed, 35 insertions(+), 33 deletions(-) >> >> diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c >> index 744dfc561db2..feb29bb92a77 100644 >> --- a/drivers/spi/spi-fsl-dspi.c >> +++ b/drivers/spi/spi-fsl-dspi.c >> @@ -591,11 +591,10 @@ static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi) >> >> static void dspi_setup_accel(struct fsl_dspi *dspi); >> >> -static int dspi_dma_xfer(struct fsl_dspi *dspi) >> +static void dspi_dma_xfer(struct fsl_dspi *dspi) >> { >> struct spi_message *message = dspi->cur_msg; >> struct device *dev = &dspi->pdev->dev; >> - int ret = 0; >> >> /* >> * dspi->len gets decremented by dspi_pop_tx_pushr in >> @@ -612,14 +611,12 @@ static int dspi_dma_xfer(struct fsl_dspi *dspi) >> message->actual_length += dspi->words_in_flight * >> dspi->oper_word_size; >> >> - ret = dspi_next_xfer_dma_submit(dspi); >> - if (ret) { >> + message->status = dspi_next_xfer_dma_submit(dspi); >> + if (message->status) { >> dev_err(dev, "DMA transfer failed\n"); >> break; >> } >> } >> - >> - return ret; >> } >> >> static int dspi_request_dma(struct fsl_dspi *dspi, phys_addr_t phy_addr) >> @@ -986,36 +983,40 @@ static void dspi_fifo_write(struct fsl_dspi *dspi) >> dspi->progress, !dspi->irq); >> } >> >> -static int dspi_rxtx(struct fsl_dspi *dspi) >> +static void dspi_rxtx(struct fsl_dspi *dspi) >> { >> dspi_fifo_read(dspi); >> >> if (!dspi->len) >> /* Success! */ >> - return 0; >> + return; >> >> dspi_fifo_write(dspi); >> - >> - return -EINPROGRESS; >> } >> >> -static int dspi_poll(struct fsl_dspi *dspi) >> +static void dspi_poll(struct fsl_dspi *dspi) >> { >> int tries = 1000; >> u32 spi_sr; >> >> - do { >> - regmap_read(dspi->regmap, SPI_SR, &spi_sr); >> - regmap_write(dspi->regmap, SPI_SR, spi_sr); >> + while (dspi->len) { > > Preivous have not checked dspi->len. > > Not sure if it is logical equivalence > It used to be this: status = dspi_poll(dspi); } while (status == -EINPROGRESS); Where checking status for -EINPROGRESS is equivalent to checking dspi->len. >> + do { >> + regmap_read(dspi->regmap, SPI_SR, &spi_sr); >> + regmap_write(dspi->regmap, SPI_SR, spi_sr); >> >> - if (spi_sr & SPI_SR_CMDTCF) >> - break; >> - } while (--tries); >> + if (spi_sr & SPI_SR_CMDTCF) >> + break; >> + } while (--tries); >> >> - if (!tries) >> - return -ETIMEDOUT; >> + if (!tries) { >> + dspi->cur_msg->status = -ETIMEDOUT; >> + return; >> + } >> >> - return dspi_rxtx(dspi); >> + dspi_rxtx(dspi); >> + } >> + >> + dspi->cur_msg->status = 0; >> } >> >> static irqreturn_t dspi_interrupt(int irq, void *dev_id) >> @@ -1029,8 +1030,13 @@ static irqreturn_t dspi_interrupt(int irq, void *dev_id) >> if (!(spi_sr & SPI_SR_CMDTCF)) >> return IRQ_NONE; >> >> - if (dspi_rxtx(dspi) == 0) >> + dspi_rxtx(dspi); >> + >> + if (!dspi->len) { >> + if (dspi->cur_msg) >> + WRITE_ONCE(dspi->cur_msg->status, 0); >> complete(&dspi->xfer_done); >> + } >> >> return IRQ_HANDLED; >> } >> @@ -1060,7 +1066,6 @@ static int dspi_transfer_one_message(struct spi_controller *ctlr, >> struct spi_device *spi = message->spi; >> struct spi_transfer *transfer; >> bool cs = false; >> - int status = 0; >> u32 val = 0; >> bool cs_change = false; >> >> @@ -1120,7 +1125,7 @@ static int dspi_transfer_one_message(struct spi_controller *ctlr, >> dspi->progress, !dspi->irq); >> >> if (dspi->devtype_data->trans_mode == DSPI_DMA_MODE) { >> - status = dspi_dma_xfer(dspi); >> + dspi_dma_xfer(dspi); >> } else { >> /* >> * Reset completion counter to clear any extra >> @@ -1133,15 +1138,12 @@ static int dspi_transfer_one_message(struct spi_controller *ctlr, >> >> dspi_fifo_write(dspi); >> >> - if (dspi->irq) { >> + if (dspi->irq) >> wait_for_completion(&dspi->xfer_done); >> - } else { >> - do { >> - status = dspi_poll(dspi); >> - } while (status == -EINPROGRESS); >> - } >> + else >> + dspi_poll(dspi); >> } >> - if (status) >> + if (READ_ONCE(message->status)) > > Why need READ_ONCE()? Does any hardware (DMA) set status? > > where update message->status at pio mode. > > Frank Because message->status is set from dspi_interrupt(), so the compiler wouldn't be aware that this variable can be changed from elsewhere. Otherwise it could assume that it's never written to in dspi_transfer_one_message() and not bother to read it again. >> break; >> >> spi_transfer_delay_exec(transfer); >> @@ -1150,7 +1152,8 @@ static int dspi_transfer_one_message(struct spi_controller *ctlr, >> dspi_deassert_cs(spi, &cs); >> } >> >> - if (status || !cs_change) { >> + dspi->cur_msg = NULL; >> + if (message->status || !cs_change) { >> /* Put DSPI in stop mode */ >> regmap_update_bits(dspi->regmap, SPI_MCR, >> SPI_MCR_HALT, SPI_MCR_HALT); >> @@ -1159,10 +1162,9 @@ static int dspi_transfer_one_message(struct spi_controller *ctlr, >> ; >> } >> >> - message->status = status; >> spi_finalize_current_message(ctlr); >> >> - return status; >> + return message->status; >> } >> >> static int dspi_set_mtf(struct fsl_dspi *dspi) >> >> -- >> 2.34.1 >>