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comedi: dmm32at: serialize use of paged registers

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Some of the hardware registers of the DMM-32-AT board are multiplexed,
using the least significant two bits of the Miscellaneous Control
register to select the function of registers at offsets 12 to 15:

 00 => 8254 timer/counter registers are accessible
 01 => 8255 digital I/O registers are accessible
 10 => Reserved
 11 => Calibration registers are accessible

The interrupt service routine (`dmm32at_isr()`) clobbers the bottom two
bits of the register with value 00, which would interfere with access to
the 8255 registers by the `dm32at_8255_io()` function (used for Comedi
instruction handling on the digital I/O subdevice).

Make use of the generic Comedi device spin-lock `dev->spinlock` (which
is otherwise unused by this driver) to serialize access to the
miscellaneous control register and paged registers.

Fixes: 3c501880ac ("Staging: comedi: add dmm32at driver")
Cc: stable@vger.kernel.org
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://patch.msgid.link/20260112162835.91688-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2026-01-12 16:28:35 +00:00 • committed by Greg Kroah-Hartman
parent 06d5a7afe1
commit e03b29b55f
1 changed files with 30 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

32
drivers/comedi/drivers/dmm32at.c
View file

@ -330,6 +330,7 @@ static int dmm32at_ai_cmdtest(struct comedi_device *dev,
static void dmm32at_setaitimer(struct comedi_device *dev, unsigned int nansec)
{
unsigned long irq_flags;
unsigned char lo1, lo2, hi2;
unsigned short both2;
@ -342,6 +343,9 @@ static void dmm32at_setaitimer(struct comedi_device *dev, unsigned int nansec)
/* set counter clocks to 10MHz, disable all aux dio */
outb(0, dev->iobase + DMM32AT_CTRDIO_CFG_REG);
/* serialize access to control register and paged registers */
spin_lock_irqsave(&dev->spinlock, irq_flags);
/* get access to the clock regs */
outb(DMM32AT_CTRL_PAGE_8254, dev->iobase + DMM32AT_CTRL_REG);
@ -354,6 +358,8 @@ static void dmm32at_setaitimer(struct comedi_device *dev, unsigned int nansec)
outb(lo2, dev->iobase + DMM32AT_CLK2);
outb(hi2, dev->iobase + DMM32AT_CLK2);
spin_unlock_irqrestore(&dev->spinlock, irq_flags);
/* enable the ai conversion interrupt and the clock to start scans */
outb(DMM32AT_INTCLK_ADINT |
DMM32AT_INTCLK_CLKEN | DMM32AT_INTCLK_CLKSEL,
@ -363,13 +369,19 @@ static void dmm32at_setaitimer(struct comedi_device *dev, unsigned int nansec)
static int dmm32at_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
{
struct comedi_cmd *cmd = &s->async->cmd;
unsigned long irq_flags;
int ret;
dmm32at_ai_set_chanspec(dev, s, cmd->chanlist[0], cmd->chanlist_len);
/* serialize access to control register and paged registers */
spin_lock_irqsave(&dev->spinlock, irq_flags);
/* reset the interrupt just in case */
outb(DMM32AT_CTRL_INTRST, dev->iobase + DMM32AT_CTRL_REG);
spin_unlock_irqrestore(&dev->spinlock, irq_flags);
/*
* wait for circuit to settle
* we don't have the 'insn' here but it's not needed
@ -429,8 +441,13 @@ static irqreturn_t dmm32at_isr(int irq, void *d)
comedi_handle_events(dev, s);
}
/* serialize access to control register and paged registers */
spin_lock(&dev->spinlock);
/* reset the interrupt */
outb(DMM32AT_CTRL_INTRST, dev->iobase + DMM32AT_CTRL_REG);
spin_unlock(&dev->spinlock);
return IRQ_HANDLED;
}
@ -481,14 +498,25 @@ static int dmm32at_ao_insn_write(struct comedi_device *dev,
static int dmm32at_8255_io(struct comedi_device *dev,
int dir, int port, int data, unsigned long regbase)
{
unsigned long irq_flags;
int ret;
/* serialize access to control register and paged registers */
spin_lock_irqsave(&dev->spinlock, irq_flags);
/* get access to the DIO regs */
outb(DMM32AT_CTRL_PAGE_8255, dev->iobase + DMM32AT_CTRL_REG);
if (dir) {
outb(data, dev->iobase + regbase + port);
return 0;
ret = 0;
} else {
ret = inb(dev->iobase + regbase + port);
}
return inb(dev->iobase + regbase + port);
spin_unlock_irqrestore(&dev->spinlock, irq_flags);
return ret;
}
/* Make sure the board is there and put it to a known state */