linux-kernel - [PATCH v2] dcdbas: force SMI to happen when expected

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Date:	Thu, 24 Feb 2011 18:35:05 -0800 (PST)
From:	stuart h <stuart_hayes@...oo.com>
To:	linux-kernel@...r.kernel.org, douglas_warzecha@...l.com
Cc:	shyam_iyer@...l.com
Subject: [PATCH v2] dcdbas: force SMI to happen when expected

This is a reworked version of a very similar patch I sent about three weeks ago... a flaw was pointed out with the original.  That patch didn't make it into the kernel, though, so I'm just sending this one as a new patch.

The dcdbas driver can do an I/O write to cause a SMI to occur.  The SMI handler looks at certain registers and memory locations, so the SMI needs to happen immediately.  On some systems I/O writes are posted, though, causing the SMI to happen well after the "outb" occurred, which causes random failures.  Following the "outb" with an "inb" forces the write to go through even if it is posted.

This patch is against the 2.6.37.1 kernel.

Signed-off-by: Stuart Hayes <stuart_hayes@...oo.com>
---

--- linux-2.6.37/drivers/firmware/dcdbas.c	2011-01-18 10:44:44.869882461 -0500
+++ linux-2.6.37_test/drivers/firmware/dcdbas.c	2011-02-24 13:23:58.663771596 -0500
@@ -268,8 +268,10 @@ int dcdbas_smi_request(struct smi_cmd *s
 	}

 	/* generate SMI */
+	/* inb to force posted write through and make SMI happen now */
 	asm volatile (
-		"outb %b0,%w1"
+		"outb %b0,%w1\n"
+		"inb %w1"
 		: /* no output args */
 		: "a" (smi_cmd->command_code),
 		  "d" (smi_cmd->command_address),

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