linux-kernel - [RFC][PATCH 1/3 v2] ARM: OMAP: DMA: Add support for DMA channel self linking on OMAP1510

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <200908231756.13016.jkrzyszt@tis.icnet.pl>
Date:	Sun, 23 Aug 2009 17:56:12 +0200
From:	Janusz Krzysztofik <jkrzyszt@....icnet.pl>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Jarkko Nikula <jhnikula@...il.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Peter Ujfalusi <peter.ujfalusi@...ia.com>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [RFC][PATCH 1/3 v2] ARM: OMAP: DMA: Add support for DMA channel self linking on OMAP1510

Implement DMA channel self linking on OMAP1510 using AUTO_INIT and REPEAT
flags of the DMA CCR register.

Created against linux-2.6.31-rc5.

Tested on Amstrad Delta.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@....icnet.pl>

---
I'm sorry, but the original patch appears to have an issue. To be honest, I
started with the one I submit here as v2, got pretty good results, then
modified it in order to better fit into existing framework, and did not test
it well enough after the change.

The problem reveals itself when an application keeps a stream open while
cycling through playing sounds. I don't know if that particular application
may just behave wrong, however, I know that setting AUTO_INIT and REPEAT
flags once after opening a stream and unsetting them once before closing it
gives stable, correct results, while redoing it for every single piece of
sound without closing the stream in between, like the current patch does,
results in inaccurate transfer startups and random application hangups.

I know it's not very fair to change the patch after others that depend on it
have already been applied, but I hope there will be no problems with accepting
the way I have reimplemented it. In any case, I'll appreciate any comments or
suggestions.

--- linux-2.6.31-rc5/arch/arm/plat-omap/dma.c.orig	2009-08-23 02:24:46.000000000 +0200
+++ linux-2.6.31-rc5/arch/arm/plat-omap/dma.c	2009-08-23 14:53:48.000000000 +0200
@@ -1131,6 +1131,11 @@ int omap_dma_running(void)
 void omap_dma_link_lch(int lch_head, int lch_queue)
 {
 	if (omap_dma_in_1510_mode()) {
+		if (lch_head == lch_queue) {
+			dma_write(dma_read(CCR(lch_head)) | (3 << 8),
+								CCR(lch_head));
+			return;
+		}
 		printk(KERN_ERR "DMA linking is not supported in 1510 mode\n");
 		BUG();
 		return;
@@ -1153,6 +1158,11 @@ EXPORT_SYMBOL(omap_dma_link_lch);
 void omap_dma_unlink_lch(int lch_head, int lch_queue)
 {
 	if (omap_dma_in_1510_mode()) {
+		if (lch_head == lch_queue) {
+			dma_write(dma_read(CCR(lch_head)) & ~(3 << 8),
+								CCR(lch_head));
+			return;
+		}
 		printk(KERN_ERR "DMA linking is not supported in 1510 mode\n");
 		BUG();
 		return;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/