6.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
commit 7d3b793faaab1305994ce568b59d61927235f57b upstream.
When enabling access to the special register set, Receiver time-out and
RHR interrupts can happen. In this case, the IRQ handler will try to read
from the FIFO thru the RHR register at address 0x00, but address 0x00 is
mapped to DLL register, resulting in erroneous FIFO reading.
Call graph example:
sc16is7xx_startup(): entry
sc16is7xx_ms_proc(): entry
sc16is7xx_set_termios(): entry
sc16is7xx_set_baud(): DLH/DLL = $009C --> access special register set
sc16is7xx_port_irq() entry --> IIR is 0x0C
sc16is7xx_handle_rx() entry
sc16is7xx_fifo_read(): --> unable to access FIFO (RHR) because it is
mapped to DLL (LCR=LCR_CONF_MODE_A)
sc16is7xx_set_baud(): exit --> Restore access to general register set
Fix the problem by claiming the efr_lock mutex when accessing the Special
register set.
Fixes: dfeae619d781 ("serial: sc16is7xx")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240723125302.1305372-3-hugo@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/sc16is7xx.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -591,6 +591,8 @@ static int sc16is7xx_set_baud(struct uar
SC16IS7XX_MCR_CLKSEL_BIT,
prescaler == 1 ? 0 : SC16IS7XX_MCR_CLKSEL_BIT);
+ mutex_lock(&one->efr_lock);
+
/* Backup LCR and access special register set (DLL/DLH) */
lcr = sc16is7xx_port_read(port, SC16IS7XX_LCR_REG);
sc16is7xx_port_write(port, SC16IS7XX_LCR_REG,
@@ -605,6 +607,8 @@ static int sc16is7xx_set_baud(struct uar
/* Restore LCR and access to general register set */
sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, lcr);
+ mutex_unlock(&one->efr_lock);
+
return DIV_ROUND_CLOSEST((clk / prescaler) / 16, div);
}
