Problem with understanding DMA on some machines (known solution!), specs needed?

[Michael Büsch]

On Tue, 26 Jul 2011 18:32:15 +0200
Rafał Miłecki <zajec5 at gmail.com> wrote:

> W dniu 26 lipca 2011 17:33 użytkownik Larry Finger
> <Larry.Finger at lwfinger.net> napisał:
> > On 07/26/2011 03:24 AM, Rafał Miłecki wrote:
> >>
> >> W dniu 25 lipca 2011 23:54 użytkownik Rafał Miłecki<zajec5 at gmail.com>
> >>  napisał:
> >>>
> >>> Now, the question: when for real we should use such a solution?
> >>>
> >>> Larry, could you check your driver? Can you see anything about this?
> >>> Is this maybe PCI (not PCIe!) specific?
> >>
> >> I've checked thread "Interesting 14e4:4321". It seems both: 14e4:4321
> >> and 14e4:4322 are using PCI slot and both are not working in DMA mode.
> >> I start believing it's PCI specific.
> >>
> >> If you take a look at current ssb code and defines:
> >>>
> >>> if (ssb_read32(dev, SSB_TMSHIGH)&  SSB_TMSHIGH_DMA64)
> >>>        return SSB_PCIE_DMA_H32;
> >>> else
> >>>        return SSB_PCI_DMA;
> >>
> >> You can see 0x80000000 (SSB_PCIE_DMA_H32) has actually "PCIE" in it's
> >> name. This can be true that 0x80000000 is *only* for *64-bit DMA* on
> >> *PCIe*.
> >
> > That is almost correct. This time I found it. The pseudo code is:
> >
> > dma_addr_lo = 0
> > dma_addr_hi = 0
> > if PCI || PCIe
> >        if PCIe && 64-bit DMA
> >                dma_addr_hi = 0x80000000
> >        else
> >                if chipID is 0x4322, 43221, 43231, or 43222
> >                        dma_addr_lo = 0x80000000
> >                else
> >                        dma_addr_lo = 0x40000000    <== your case
> >
> > Thus it is just a little more complicated than a PCI/PCIe split, as it also
> > depends on the chip ID.
> >
> > I'll add this to the specs.
> 
> Can you (anyone, not just Larry ;) ) give me some tip, how to
> implement this correctly? From programming POV.
> 
> We should return two infos from ssb code now:
> 1) Routing bit
> 2) Address which should be used
> 
> Should I add new function for this? Or create struct
> dma_translation_info with 2 fields? Or return array? Or...?

I would do it something like this (completely untested. Not even compiled):


Index: wireless-testing/drivers/ssb/main.c
===================================================================
--- wireless-testing.orig/drivers/ssb/main.c	2011-07-21 23:20:56.000000000 +0200
+++ wireless-testing/drivers/ssb/main.c	2011-07-26 20:50:31.920182657 +0200
@@ -1260,16 +1260,32 @@ void ssb_device_disable(struct ssb_devic
 }
 EXPORT_SYMBOL(ssb_device_disable);
 
+static bool let_the_software_guys_fix_it(struct ssb_device *dev)
+{
+	u16 chip_id = dev->bus->chip_id;
+
+	if (dev->id.coreid == SSB_DEV_80211) {
+		return (chip_id == 0x4322 || chip_id == 43221 ||
+			chip_id == 43231 || chip_id == 43222)
+	}
+	return 0;
+}
+
 u32 ssb_dma_translation(struct ssb_device *dev)
 {
 	switch (dev->bus->bustype) {
 	case SSB_BUSTYPE_SSB:
 		return 0;
 	case SSB_BUSTYPE_PCI:
-		if (ssb_read32(dev, SSB_TMSHIGH) & SSB_TMSHIGH_DMA64)
+		if (dev->bus->host_pci->is_pcie &&
+		    (ssb_read32(dev, SSB_TMSHIGH) & SSB_TMSHIGH_DMA64)) {
 			return SSB_PCIE_DMA_H32;
-		else
-			return SSB_PCI_DMA;
+		} else {
+			if (let_the_software_guys_fix_it(dev))
+				return SSB_PCIE_DMA_H32;
+			else
+				return SSB_PCI_DMA;
+		}
 	default:
 		__ssb_dma_not_implemented(dev);
 	}
Index: wireless-testing/drivers/net/wireless/b43/dma.c
===================================================================
--- wireless-testing.orig/drivers/net/wireless/b43/dma.c	2011-07-21 23:20:55.000000000 +0200
+++ wireless-testing/drivers/net/wireless/b43/dma.c	2011-07-26 20:53:40.688974405 +0200
@@ -1052,6 +1052,21 @@ static int b43_dma_set_mask(struct b43_w
 	return 0;
 }
 
+static bool dma_translation_in_low_word(struct b43_wldev *dev)
+{
+#ifdef CONFIG_B43_SSB
+	if (dev->dev->bus_type != B43_BUS_SSB)
+		return 0;
+	if (dev->dev->sdev->bus->bustype == SSB_BUSTYPE_PCI) {
+		if (dev->dev->sdev->bus->host_pci->is_pcie &&
+		    (ssb_read32(dev->dev->sdev, SSB_TMSHIGH) & SSB_TMSHIGH_DMA64))
+			return 0;
+		return 1;
+	}
+#endif
+	return 0;
+}
+
 int b43_dma_init(struct b43_wldev *dev)
 {
 	struct b43_dma *dma = &dev->dma;
@@ -1074,6 +1089,7 @@ int b43_dma_init(struct b43_wldev *dev)
 #ifdef CONFIG_B43_SSB
 	case B43_BUS_SSB:
 		dma->translation = ssb_dma_translation(dev->dev->sdev);
+		//Hurr durr use dma_translation_in_low_word()
 		break;
 #endif
 	}

-- 
Greetings, Michael.