linux-kernel - Re: [PATCH v2] sata_sil24: Use memory barriers before issuing commands

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Message-ID: <4C1147B2.7090207@garzik.org>
Date:	Thu, 10 Jun 2010 16:14:42 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>,
	Colin Tuckley <colin.tuckley@....com>
Subject: Re: [PATCH v2] sata_sil24: Use memory barriers before issuing commands

On 06/10/2010 12:02 PM, Catalin Marinas wrote:
> The data in the cmd_block buffers may reach the main memory after the
> writel() to the device ports. This patch introduces two calls to wmb()
> to ensure the relative ordering.
>
> Signed-off-by: Catalin Marinas<catalin.marinas@....com>
> Tested-by: Colin Tuckley<colin.tuckley@....com>
> Cc: Tejun Heo<tj@...nel.org>
> Cc: Jeff Garzik<jeff@...zik.org>
> ---
>   drivers/ata/sata_sil24.c |   10 ++++++++++
>   1 files changed, 10 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
> index e925051..a5d5aff 100644
> --- a/drivers/ata/sata_sil24.c
> +++ b/drivers/ata/sata_sil24.c
> @@ -622,6 +622,11 @@ static int sil24_exec_polled_cmd(struct ata_port *ap, int pmp,
>   	irq_enabled = readl(port + PORT_IRQ_ENABLE_SET);
>   	writel(PORT_IRQ_COMPLETE | PORT_IRQ_ERROR, port + PORT_IRQ_ENABLE_CLR);
>
> +	/*
> +	 * The barrier is required to ensure that writes to cmd_block reach
> +	 * the memory before the write to PORT_CMD_ACTIVATE.
> +	 */
> +	wmb();
>   	writel((u32)paddr, port + PORT_CMD_ACTIVATE);
>   	writel((u64)paddr>>  32, port + PORT_CMD_ACTIVATE + 4);
>
> @@ -895,6 +900,11 @@ static unsigned int sil24_qc_issue(struct ata_queued_cmd *qc)
>   	paddr = pp->cmd_block_dma + tag * sizeof(*pp->cmd_block);
>   	activate = port + PORT_CMD_ACTIVATE + tag * 8;
>
> +	/*
> +	 * The barrier is required to ensure that writes to cmd_block reach
> +	 * the memory before the write to PORT_CMD_ACTIVATE.
> +	 */
> +	wmb();
>   	writel((u32)paddr, activate);
>   	writel((u64)paddr>>  32, activate + 4);
>

applied


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