Commit e03b29b5 authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman
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comedi: dmm32at: serialize use of paged registers 



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: 3c501880 ("Staging: comedi: add dmm32at driver")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Link: https://patch.msgid.link/20260112162835.91688-1-abbotti@mev.co.uk


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 06d5a7af

drivers/comedi/drivers/dmm32at.c

+30 −2
Original line number Diff line number Diff line
@@ -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 */