Re: [PATCH v2] dmaengine: imx-sdma: fix incorrect conversion to readl_relaxed_poll_timeout_atomic()

[Russell King - ARM Linux admin <linux@armlinux.org.uk>]

On Sat, Jun 22, 2019 at 08:26:53PM +0100, Russell King - ARM Linux admin wrote:
> Well, this doesn't appear to completely solve the problem either -
> one out of four of my platforms still spat out the error (because
> the SDMA initialisation can run on a different CPU to that which
> receives the interrupt.)
> 
> I've thought about using a completion, but that doesn't work either,
> because in the case of a single CPU, the interrupts will be masked,
> so we can't wait for completion.  I think we need to eliminate that
> spinlock around this code.

It looks like iMX6 Dual does not initialise DMA properly using the 1.1
firmware - md5sum is:

5d4584134cc4cba62e1be2f382cd6f3a  /lib/firmware/imx/sdma/sdma-imx6q.bin

I've tried extending the timeout to 5ms, checking HI[0] (both from the
interrupt handler and from sdma_run_channel0() to cover the case of a
single-core setup).

After boot:

 60:          0          0       GPC   2 Level     sdma

So no interrupt was received.  Looking at the registers:

# /shared/bin32/devmem2 0x20ec02c
Value at address 0x020ec02c: 0x00000000  <= H_INTRMASK
# /shared/bin32/devmem2 0x20ec004
Value at address 0x020ec004: 0x00000000  <= H_INTR
# /shared/bin32/devmem2 0x20ec00c
Value at address 0x020ec00c: 0x00000000  <= H_START
# /shared/bin32/devmem2 0x20ec008
Value at address 0x020ec008: 0x00000001  <= H_STATSTOP

Any ideas?

> 
> On Sat, Jun 22, 2019 at 07:55:53PM +0100, Russell King wrote:
> > When imx-sdma was converted to use readl_relaxed_poll_timeout_atomic(),
> > the termination condition was inverted.  Fix this.
> > 
> > Fixes: 1d069bfa3c78 ("dmaengine: imx-sdma: ack channel 0 IRQ in the interrupt handler")
> > Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
> > ---
> >  drivers/dma/imx-sdma.c | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> > index 5f3c1378b90e..c45cbdb09714 100644
> > --- a/drivers/dma/imx-sdma.c
> > +++ b/drivers/dma/imx-sdma.c
> > @@ -655,15 +655,21 @@ static void sdma_enable_channel(struct sdma_engine *sdma, int channel)
> >  static int sdma_run_channel0(struct sdma_engine *sdma)
> >  {
> >  	int ret;
> > -	u32 reg;
> > +	u32 reg, mask;
> > +
> > +	// Disable channel 0 interrupt
> > +	mask = readl_relaxed(sdma->regs + SDMA_H_INTRMSK);
> > +	writel_relaxed(mask & ~1, sdma->regs + SDMA_H_INTRMSK);
> >  
> >  	sdma_enable_channel(sdma, 0);
> >  
> > -	ret = readl_relaxed_poll_timeout_atomic(sdma->regs + SDMA_H_STATSTOP,
> > -						reg, !(reg & 1), 1, 500);
> > +	ret = readl_relaxed_poll_timeout_atomic(sdma->regs + SDMA_H_INTR,
> > +						reg, reg & 1, 1, 500);
> >  	if (ret)
> >  		dev_err(sdma->dev, "Timeout waiting for CH0 ready\n");
> >  
> > +	writel_relaxed(mask, sdma->regs + SDMA_H_INTRMSK);
> > +
> >  	/* Set bits of CONFIG register with dynamic context switching */
> >  	reg = readl(sdma->regs + SDMA_H_CONFIG);
> >  	if ((reg & SDMA_H_CONFIG_CSM) == 0) {
> > -- 
> > 2.7.4
> > 
> > 
> 
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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> 
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> 

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up

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