From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Walle Subject: Re: [PATCH v3 0/7] NXP DSPI bugfixes and support for LS1028A Date: Fri, 13 Mar 2020 17:53:24 +0100 Message-ID: <4b77ccec9d0de0615985ebf60db9cf67@walle.cc> 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=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Cc: Mark Brown , linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, lkml , Shawn Guo , Rob Herring , Mark Rutland , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Esben Haabendal , angelo-BIYBQhTR83Y@public.gmane.org, andrew.smirnov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, "Gustavo A. R. Silva" , Wei Chen , Mohamed Hosny , peng.ma-3arQi8VN3Tc@public.gmane.org To: Vladimir Oltean Return-path: In-Reply-To: Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Am 2020-03-13 17:37, schrieb Vladimir Oltean: > 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. Sure. It was just a quick test whether the problem actually goes away. > 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. I didn't want to move the interrupt_enable() around. I leave this up to you ;) -michael