Re: [PATCH] ahci: retry enabling AHCI a few times before spitting out WARN_ON()

[Jeff Garzik <jeff@garzik.org>]

Tejun Heo wrote:
> Some chips need AHCI_EN set more than once to actually set it.  Try a
> few times before giving up and spitting out WARN_ON().
> 
> Signed-off-by: Tejun Heo <htejun@gmail.com>
> Cc: Peer Chen <pchen@nvidia.com>
> Cc: Volker Armin Hemmann <volker.armin.hemmann@tu-clausthal.de>
> ---
> drivers/ata/ahci.c |   15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> index 739ba3f..711b5d7 100644
> --- a/drivers/ata/ahci.c
> +++ b/drivers/ata/ahci.c
> @@ -556,16 +556,27 @@ static inline void __iomem *ahci_port_base(struct 
> ata_port *ap)
> 
> static void ahci_enable_ahci(void __iomem *mmio)
> {
> +    int i;
>     u32 tmp;
> 
>     /* turn on AHCI_EN */
>     tmp = readl(mmio + HOST_CTL);
> -    if (!(tmp & HOST_AHCI_EN)) {
> +    if (tmp & HOST_AHCI_EN)
> +        return;
> +
> +    /* Some controllers need AHCI_EN to be written multiple times.
> +     * Try a few times before giving up.
> +     */
> +    for (i = 0; i < 5; i++) {
>         tmp |= HOST_AHCI_EN;
>         writel(tmp, mmio + HOST_CTL);
>         tmp = readl(mmio + HOST_CTL);    /* flush && sanity check */
> -        WARN_ON(!(tmp & HOST_AHCI_EN));
> +        if (tmp & HOST_AHCI_EN)
> +            return;
> +        msleep(10);
>     }
> +
> +    WARN_ON(1);
> }

applied