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SubjectRe: [PATCH] spi: rspi: Fix register initialization while runtime-suspended
On Tue, Mar 12, 2019 at 7:43 PM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
> The Renesas RSPI/QSPI driver performs SPI controller register
> initialization in its spi_operations.setup() callback, without calling
> pm_runtime_get_sync() first, which may cause spurious failures.
>
> So far this went unnoticed, as this SPI controller is typically used
> with a single SPI NOR FLASH containing the boot loader:
> 1. If the device's module clock is still enabled (left enabled by the
> bootloader, and not yet disabled by the clk_disable_unused() late
> initcall), register initialization succeeds,
> 2. If the device's module clock is disabled, register writes don't
> seem to cause lock-ups or crashes.
> Data received in the first SPI message may be corrupted, though.
> Subsequent SPI messages seem to be OK.
> E.g. on r8a7791/koelsch, one bit is lost while receiving the 6th
> byte of the JEDEC ID for the s25fl512s FLASH, corrupting that byte
> and all later bytes. But until commit a2126b0a010905e5 ("mtd:
> spi-nor: refine Spansion S25FL512S ID"), the 6th byte was not
> considered for FLASH identification.
>
> Fix this by moving all initialization from the .setup() to the
> .prepare_message() callback. The latter is always called after the
> device has been runtime-resumed by the SPI core.
>
> This also makes the driver follow the rule that .setup() must not change
> global driver state or register values, as that might break a transfer
> in progress.
>
> Fixes: 490c97747d5dc77d ("spi: rspi: Add runtime PM support, using spi core auto_runtime_pm")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> This is a fix for v5.1-rc1, as a2126b0a010905e5 will be in v5.1-rc1.
> ---
> drivers/spi/spi-rspi.c | 39 ++++++++++++++++-----------------------
> 1 file changed, 16 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/spi/spi-rspi.c b/drivers/spi/spi-rspi.c
> index 556870dcdf7995f8..b30fed824e6643a2 100644
> --- a/drivers/spi/spi-rspi.c
> +++ b/drivers/spi/spi-rspi.c
> @@ -868,28 +868,6 @@ static int qspi_transfer_one(struct spi_controller *ctlr,
> }
> }
>
> -static int rspi_setup(struct spi_device *spi)
> -{
> - struct rspi_data *rspi = spi_controller_get_devdata(spi->controller);
> -
> - rspi->max_speed_hz = spi->max_speed_hz;
> -
> - rspi->spcmd = SPCMD_SSLKP;
> - if (spi->mode & SPI_CPOL)
> - rspi->spcmd |= SPCMD_CPOL;
> - if (spi->mode & SPI_CPHA)
> - rspi->spcmd |= SPCMD_CPHA;
> -
> - /* CMOS output mode and MOSI signal from previous transfer */
> - rspi->sppcr = 0;
> - if (spi->mode & SPI_LOOP)
> - rspi->sppcr |= SPPCR_SPLP;
> -
> - set_config_register(rspi, 8);
> -
> - return 0;
> -}
> -
> static u16 qspi_transfer_mode(const struct spi_transfer *xfer)
> {
> if (xfer->tx_buf)
> @@ -959,8 +937,24 @@ static int rspi_prepare_message(struct spi_controller *ctlr,
> struct spi_message *msg)
> {
> struct rspi_data *rspi = spi_controller_get_devdata(ctlr);
> + struct spi_device *spi = msg->spi;
> int ret;
>
> + rspi->max_speed_hz = spi->max_speed_hz;
> +
> + rspi->spcmd = SPCMD_SSLKP;
> + if (spi->mode & SPI_CPOL)
> + rspi->spcmd |= SPCMD_CPOL;
> + if (spi->mode & SPI_CPHA)
> + rspi->spcmd |= SPCMD_CPHA;
> +
> + /* CMOS output mode and MOSI signal from previous transfer */
> + rspi->sppcr = 0;
> + if (spi->mode & SPI_LOOP)
> + rspi->sppcr |= SPPCR_SPLP;
> +
> + set_config_register(rspi, 8);

Probably some of the operations in the (SoC-specific) set_config_register()
could be moved to .prepare_transfer_hardware(), but that can be done
in a future optimization.

> +
> if (msg->spi->mode &
> (SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD)) {
> /* Setup sequencer for messages with multiple transfer modes */
> @@ -1267,7 +1261,6 @@ static int rspi_probe(struct platform_device *pdev)
> init_waitqueue_head(&rspi->wait);
>
> ctlr->bus_num = pdev->id;
> - ctlr->setup = rspi_setup;
> ctlr->auto_runtime_pm = true;
> ctlr->transfer_one = ops->transfer_one;
> ctlr->prepare_message = rspi_prepare_message;

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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