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Subject[PATCH] spi: rspi: Fix register initialization while runtime-suspended
Date
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);
+
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;
--
2.17.1
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