linux-kernel - RE: [PATCHv3 5/9] dspbridge: add mmufault support

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Date:	Thu, 1 Jul 2010 12:54:30 -0500
From:	"Guzman Lugo, Fernando" <fernando.lugo@...com>
To:	"Kanigeri, Hari" <h-kanigeri2@...com>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"ohad@...ery.com" <ohad@...ery.com>,
	Hiroshi DOYU <Hiroshi.DOYU@...ia.com>,
	"ameya.palande@...ia.com" <ameya.palande@...ia.com>,
	"felipe.contreras@...ia.com" <felipe.contreras@...ia.com>
Subject: RE: [PATCHv3 5/9] dspbridge: add mmufault support



Hi Hari,

> -----Original Message-----
> From: Kanigeri, Hari
> Sent: Thursday, July 01, 2010 12:17 PM
> To: Guzman Lugo, Fernando; linux-omap@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Cc: ohad@...ery.com; hiroshi.doyo@...ia.com; ameya.palande@...ia.com;
> felipe.contreras@...ia.com; Guzman Lugo, Fernando
> Subject: RE: [PATCHv3 5/9] dspbridge: add mmufault support
> 
> Hi Fernando,
> 
> > +int mmu_fault_isr(struct iommu *mmu)
> >
> > -/*
> > - *  ======== mmu_check_if_fault =======
> > - *      Check to see if MMU Fault is valid TLB miss from DSP
> > - *  Note: This function is called from an ISR
> > - */
> > -static bool mmu_check_if_fault(struct bridge_dev_context *dev_context)
> >  {
> > +	struct deh_mgr *dm;
> > +	u32 da;
> > +
> > +	dev_get_deh_mgr(dev_get_first(), &dm);
> > +
> > +	if (!dm)
> > +		return -EPERM;
> > +
> > +	da = iommu_read_reg(mmu, MMU_FAULT_AD);
> > +	iommu_write_reg(mmu, 0, MMU_IRQENABLE);
> 
> -- Isn't the MMU already enabled at this point when the function callback
> is called by iommu ?

This line is actually disabling the interrupts. I am writing "0x0" in the MMU_IRQENABLE.

> 
> > +	dm->err_info.dw_val1 = da;
> > +	tasklet_schedule(&dm->dpc_tasklet);
> 
> -- The iommu fault isr disables the IOMMU at the end of the fault handler,
> so by the time your tasklet is scheduled you might have the MMU in a
> disabled state. Looks to me either this requires change in iommu to remove
> the disable part or enable the MMU in the tasklet instead of doing it
> early in mmu_fault_isr.

I am returning 0 in the callback function, that means the callback function has managed the fault and the mmu_fault_isr does not do anything else


	if (obj->isr)
		err = obj->isr(obj);

	if (!err)
		return IRQ_HANDLED;

it is working for me without not modifications in the iommu_fault_handler function.

Thanks for the comments,
Fernando.

> 
> Thank you,
> Best regards,
> Hari
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