Recently we found the fifo_read() and fifo_write() are broken in our 5.15 and 5.4 kernels after cherry-pick the commit e635f652696e ("serial: sc16is7xx: convert from _raw_ to _noinc_ regmap functions for FIFO"), that is because the reg needs to shift if we don't cherry-pick a prerequisite commit 3837a0379533 ("serial: sc16is7xx: improve regmap debugfs by using one regmap per port").
It is hard to backport the prerequisite commit to 5.15.y and 5.10.y due to the significant conflict. To be safe, here fix it by shifting the reg as regmap_volatile() does.
Cc: stable@vger.kernel.org Signed-off-by: Hui Wang hui.wang@canonical.com --- in the V2: add Cc: fix a typo on prerequisite add explanation for not backporting the prerequisite patch to 5.15.y and 5.10.y
drivers/tty/serial/sc16is7xx.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c index d274a847c6ab..87e34099f369 100644 --- a/drivers/tty/serial/sc16is7xx.c +++ b/drivers/tty/serial/sc16is7xx.c @@ -487,7 +487,14 @@ static bool sc16is7xx_regmap_precious(struct device *dev, unsigned int reg)
static bool sc16is7xx_regmap_noinc(struct device *dev, unsigned int reg) { - return reg == SC16IS7XX_RHR_REG; + switch (reg >> SC16IS7XX_REG_SHIFT) { + case SC16IS7XX_RHR_REG: + return true; + default: + break; + } + + return false; }
/*