Re: [PATCH] ahci: enable GHC.AE bit before set GHC.HR

[Jeff Garzik]

Peer Chen wrote:
> According to the description of section 5.2.2.1 and 10.1.2 of AHCI specification rev1_1/rev1_2, GHC.HR shall only be set to ¡®1¡¯
> by software when GHC.AE is set to ¡®1¡¯.
>
> Signed-off-by: Peer Chen <peerchen@xxxxxxxxx>
> ---
> --- linux-2.6.23-rc7/drivers/ata/ahci.c.orig	2007-09-20 11:01:55.000000000 -0400
> +++ linux-2.6.23-rc7/drivers/ata/ahci.c	2007-09-20 11:07:31.000000000 -0400
> @@ -834,6 +834,10 @@ static int ahci_reset_controller(struct 
>  	void __iomem *mmio = host->iomap[AHCI_PCI_BAR];
>  	u32 tmp;
>  
> +        /* turn on AHCI mode before controller reset*/
> +        writel(HOST_AHCI_EN, mmio + HOST_CTL);
> +        (void) readl(mmio + HOST_CTL);  /* flush */

applied the attached patch, inspired by yours.

commit 5fca365d6109b51cfeb3515ca660cd2dc6e8822c
Author: Jeff Garzik <jeff@xxxxxxxxxx>
Date:   Wed Sep 26 00:02:41 2007 -0400

    [libata] AHCI: enable AHCI mode, before using AHCI reset
    
    AHCI spec says host-reset bit may only be set when the ahci-enable bit
    is also set.
    
    Noticed by Peer Chen <peerchen@xxxxxxxxx>
    
    Signed-off-by: Jeff Garzik <jeff@xxxxxxxxxx>

 drivers/ata/ahci.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

5fca365d6109b51cfeb3515ca660cd2dc6e8822c
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 9f3c591..b615390 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -827,8 +827,14 @@ static int ahci_reset_controller(struct ata_host *host)
 	void __iomem *mmio = host->iomap[AHCI_PCI_BAR];
 	u32 tmp;
 
-	/* global controller reset */
+	/* we must be in AHCI mode, before using anything
+	 * AHCI-specific, such as HOST_RESET.
+	 */
 	tmp = readl(mmio + HOST_CTL);
+	if (!(tmp & HOST_AHCI_EN))
+		writel(tmp | HOST_AHCI_EN, mmio + HOST_CTL);
+
+	/* global controller reset */
 	if ((tmp & HOST_RESET) == 0) {
 		writel(tmp | HOST_RESET, mmio + HOST_CTL);
 		readl(mmio + HOST_CTL); /* flush */