From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladimir Oltean Subject: Re: [PATCH v3 0/7] NXP DSPI bugfixes and support for LS1028A Date: Fri, 13 Mar 2020 18:37:39 +0200 Message-ID: References: <20200310125542.5939-1-olteanv@gmail.com> <615284875b709f602d57e4a4621a83c1@walle.cc> <59b07b7d70603c6b536a7354ed0ea8d8@walle.cc> <4ba077c80143c8ec679066e6d8cedca2@walle.cc> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: Mark Brown , linux-spi@vger.kernel.org, lkml , Shawn Guo , Rob Herring , Mark Rutland , devicetree@vger.kernel.org, Esben Haabendal , angelo@sysam.it, andrew.smirnov@gmail.com, "Gustavo A. R. Silva" , Wei Chen , Mohamed Hosny , peng.ma@nxp.com To: Michael Walle Return-path: In-Reply-To: <4ba077c80143c8ec679066e6d8cedca2@walle.cc> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-spi.vger.kernel.org Hi Michael, On Fri, 13 Mar 2020 at 18:07, Michael Walle wrote: > > Am 2020-03-10 16:22, schrieb Michael Walle: > > Hi Vladimir, > > > > Am 2020-03-10 15:56, schrieb Vladimir Oltean: > >>> (2) Also, reading the flash, every second time there is > >>> (reproducibly) > >>> an > >>> IO error: > >>> > >>> # hexdump -C /dev/mtd0 > >>> 00000000 68 75 68 75 0a ff ff ff ff ff ff ff ff ff ff ff > >>> |huhu............| > >>> 00000010 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > >>> |................| > >>> * > >>> 01000000 > >>> # hexdump -C /dev/mtd0 > >>> 00000000 68 75 68 75 0a ff ff ff ff ff ff ff ff ff ff ff > >>> |huhu............| > >>> 00000010 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > >>> |................| > >>> * > >>> hexdump: /dev/mtd0: Input/output error > >>> 00dc0000 > >>> # hexdump -C /dev/mtd0 > >>> 00000000 68 75 68 75 0a ff ff ff ff ff ff ff ff ff ff ff > >>> |huhu............| > >>> 00000010 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > >>> |................| > >>> * > >>> 01000000 > >>> # hexdump -C /dev/mtd0 > >>> 00000000 68 75 68 75 0a ff ff ff ff ff ff ff ff ff ff ff > >>> |huhu............| > >>> 00000010 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > >>> |................| > >>> * > >>> hexdump: /dev/mtd0: Input/output error > >>> 00e6a000 > >>> > >> > >> Just to be clear, issue 2 is seen only after you abort another > >> transaction, right? > > > > No, just normal uninterrupted reading. Just tried it right after > > reboot. Doesn't seem to be every second time though, just random > > which makes me wonder if that is another problem now. Also the > > last successful reading is random. > > > Ok I guess I know what the root cause is. This is an extract of > the current code: > > > static int dspi_transfer_one_message(struct spi_controller *ctlr, > > struct spi_message *message) > > { > > .. > > /* Kick off the interrupt train */ > > dspi_fifo_write(dspi); > > > > status = wait_event_interruptible(dspi->waitq, > > dspi->waitflags); > > dspi->waitflags = 0; > > .. > > } > > > > static int dspi_rxtx(struct fsl_dspi *dspi) > > { > > dspi_fifo_read(dspi); > > > > if (!dspi->len) > > /* Success! */ > > return 0; > > > > dspi_fifo_write(dspi); > > > > return -EINPROGRESS; > > } > > dspi_rxtx() is used in the ISR. Both dspi_fifo_write() and dspi_rxtx() > access shared data like, dspi->words_in_flight. In the EIO error case > the following bytes_sent is -1, because dspi->words_in_flight is -1. > > > /* Update total number of bytes that were transferred */ > > bytes_sent = dspi->words_in_flight * dspi->oper_word_size; > > words_in_flight is always -1 after dspi_fifo_read() was called. In > the error case, the ISR kicks in right in the middle of the execution > of dspi_fifo_write() in dspi_transfer_one_message(). > > > static void dspi_fifo_write(struct fsl_dspi *dspi) > > { > > .. > > if (dspi->devtype_data->trans_mode == DSPI_EOQ_MODE) > > dspi_eoq_fifo_write(dspi); > > else > > dspi_xspi_fifo_write(dspi); > > Now if the ISR is executed right here.. > > > > > /* Update total number of bytes that were transferred */ > > bytes_sent = dspi->words_in_flight * dspi->oper_word_size; > > .. words_in_flight might be -1. > > > msg->actual_length += bytes_sent; > > and bytes_sent is negative. And this causes an IO error because > the returned overall message length doesn't match. > > > dspi->progress += bytes_sent / DIV_ROUND_UP(xfer->bits_per_word, 8); > > .. > > } > > I could not reproduce the issue with the following patch. I don't > know if I got the locking correct though or if there is a better > way to go. > > > diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c > index 8b16de9ed382..578fedeb16a0 100644 > --- a/drivers/spi/spi-fsl-dspi.c > +++ b/drivers/spi/spi-fsl-dspi.c > @@ -224,6 +224,7 @@ struct fsl_dspi { > u16 tx_cmd; > const struct fsl_dspi_devtype_data *devtype_data; > > + spinlock_t lock; > wait_queue_head_t waitq; > u32 waitflags; > > @@ -873,14 +874,20 @@ static void dspi_fifo_write(struct fsl_dspi *dspi) > > static int dspi_rxtx(struct fsl_dspi *dspi) > { > + unsigned long flags; > + > + spin_lock_irqsave(&dspi->lock, flags); > dspi_fifo_read(dspi); > > - if (!dspi->len) > + if (!dspi->len) { > /* Success! */ > + spin_unlock_irqrestore(&dspi->lock, flags); > return 0; > + } > > dspi_fifo_write(dspi); > > + spin_unlock_irqrestore(&dspi->lock, flags); > return -EINPROGRESS; > } > > @@ -950,7 +957,9 @@ static int dspi_transfer_one_message(struct > spi_controller *ctlr, > struct fsl_dspi *dspi = spi_controller_get_devdata(ctlr); > struct spi_device *spi = message->spi; > struct spi_transfer *transfer; > + unsigned long flags; > int status = 0; > + int i = 0; > > if (dspi->irq) > dspi_enable_interrupts(dspi, true); > @@ -1009,7 +1018,9 @@ static int dspi_transfer_one_message(struct > spi_controller *ctlr, > goto out; > } else if (dspi->irq) { > /* Kick off the interrupt train */ > + spin_lock_irqsave(&dspi->lock, flags); > dspi_fifo_write(dspi); > + spin_unlock_irqrestore(&dspi->lock, flags); > > status = wait_event_interruptible(dspi->waitq, > > dspi->waitflags); > @@ -1301,6 +1312,7 @@ static int dspi_probe(struct platform_device > *pdev) > ctlr->cleanup = dspi_cleanup; > ctlr->slave_abort = dspi_slave_abort; > ctlr->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST; > + spin_lock_init(&dspi->lock); > > pdata = dev_get_platdata(&pdev->dev); > if (pdata) { > > > > -michael Thanks for taking such a close look. I haven't had the time to follow up. Indeed, the ISR, and therefore dspi_fifo_read, can execute before dspi->words_in_flight was populated correctly. And bad things will happen in that case. But I wouldn't introduce a spin lock that disables interrupts on the local CPU just for that - it's too complicated for this driver. I would just keep the SPI interrupt quiesced via SPI_RSER and enable it only once it's safe, aka after updating dspi->words_in_flight. Thanks, -Vladimir