[OpenWrt-Devel] [PATCH 2/2] apm821xx: attempt to fix sata access freezes

[Christian Lamparter]

The original vendor's driver programmed the dma controller's
AHB HPROT values to enable bufferable, privileged mode. This
along with the "same priorty for both channels" could very
well fix the freezes that have been reported on the forum by
@ticerex and @takimata.

<https://forum.lede-project.org/t/wd-mybook-live-duo-two-disks/16195/46>
Signed-off-by: Christian Lamparter <chunkeey at gmail.com>
---
Awaiting confirmation from the original reporters. But if
this turns out to fix the issue, I'll do a separate patch for
18.06 and lede-17.01.
---
 ...-dw-dma-hprot-fix-and-equal-priortiy.patch | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 target/linux/apm821xx/patches-4.14/302-dw-dma-hprot-fix-and-equal-priortiy.patch

diff --git a/target/linux/apm821xx/patches-4.14/302-dw-dma-hprot-fix-and-equal-priortiy.patch b/target/linux/apm821xx/patches-4.14/302-dw-dma-hprot-fix-and-equal-priortiy.patch
new file mode 100644
index 0000000000..c6e4331aa9
--- /dev/null
+++ b/target/linux/apm821xx/patches-4.14/302-dw-dma-hprot-fix-and-equal-priortiy.patch
@@ -0,0 +1,25 @@
+--- a/drivers/dma/dw/core.c
++++ b/drivers/dma/dw/core.c
+@@ -167,6 +167,8 @@ static void dwc_initialize_chan_dw(struc
+ 	cfghi |= DWC_CFGH_DST_PER(dwc->dws.dst_id);
+ 	cfghi |= DWC_CFGH_SRC_PER(dwc->dws.src_id);
+ 
++	cfghi |= DWC_CFGH_PROTCTL(3); /* bufferable + privileged access */
++
+ 	/* Set polarity of handshake interface */
+ 	cfglo |= hs_polarity ? DWC_CFGL_HS_DST_POL | DWC_CFGL_HS_SRC_POL : 0;
+ 
+@@ -1293,11 +1295,8 @@ int dw_dma_probe(struct dw_dma_chip *chi
+ 		else
+ 			list_add(&dwc->chan.device_node, &dw->dma.channels);
+ 
+-		/* 7 is highest priority & 0 is lowest. */
+-		if (pdata->chan_priority == CHAN_PRIORITY_ASCENDING)
+-			dwc->priority = pdata->nr_channels - i - 1;
+-		else
+-			dwc->priority = i;
++		/* set all channels to the same priority */
++		dwc->priority = pdata->nr_channels - 1;
+ 
+ 		dwc->ch_regs = &__dw_regs(dw)->CHAN[i];
+ 		spin_lock_init(&dwc->lock);
-- 
2.18.0


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