linux-kernel - Re: [PATCH 3/4] mmc: sunxi: Reset behavior fix

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Date:	Tue, 16 Dec 2014 10:57:10 +0100
From:	Hans de Goede <hdegoede@...hat.com>
To:	David Lanzendörfer 
	<david.lanzendoerfer@....ch>, Ulf Hansson <ulf.hansson@...aro.org>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Arnd Bergmann <arnd@...db.de>, linux-mmc@...r.kernel.org,
	Chris Ball <chris@...ntf.net>, linux-kernel@...r.kernel.org,
	Peter Griffin <peter.griffin@...aro.org>,
	Chen-Yu Tsai <wens@...e.org>,
	李想 <lixiang@...winnertech.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/4] mmc: sunxi: Reset behavior fix

Hi,

On 16-12-14 01:37, David Lanzendörfer wrote:
> When there is only one DES available the DMA performs a FIFO reset and waits until the reinitialization has been completed.
> Disabling the SDXC_IDMAC_DES0_DIC bit prevents the DMA from sending an interrupt after it has finished this reinitialization.
>
> The flags SDXC_IDMAC_DES0_FD and SDXC_IDMAC_DES0_LD are both required in order to use the controller with more than one DES.
>
> Signed-off-by: David Lanzendörfer <david.lanzendoerfer@....ch>
> Reported-by: 李想 <lixiang@...winnertech.com>
> ---
>   drivers/mmc/host/sunxi-mmc.c |   12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
> index 50bd3d2..5331c88 100644
> --- a/drivers/mmc/host/sunxi-mmc.c
> +++ b/drivers/mmc/host/sunxi-mmc.c
> @@ -310,7 +310,17 @@ static void sunxi_mmc_init_idma_des(struct sunxi_mmc_host *host,
>   	}
>
>   	pdes[0].config |= SDXC_IDMAC_DES0_FD;
> -	pdes[i - 1].config = SDXC_IDMAC_DES0_OWN | SDXC_IDMAC_DES0_LD;
> +
> +	/*
> +	 * When there is only one DES available the DMA performs a FIFO reset and waits
> +	 * until the reinitialization has been completed.
> +	 * Disabling the SDXC_IDMAC_DES0_DIC bit prevents the DMA from sending an interrupt
> +	 * after it has finished this reinitialization.
> +	 */
> +	pdes[i - 1].config = SDXC_IDMAC_DES0_OWN;
> +	pdes[i - 1].config |= SDXC_IDMAC_DES0_FD;
> +	pdes[i - 1].config |= SDXC_IDMAC_DES0_LD;
> +	pdes[i - 1].config &= ~SDXC_IDMAC_DES0_DIC;
>
>   	/*
>   	 * Avoid the io-store starting the idmac hitting io-mem before the

This is wrong. For one you are starting with an assignment, so you could just as well
set all the flags you want with a single line / assignment. Besides that you're setting
the FD flag, which should only be set for the first descriptor of a transfer, so for
multi descriptor transfers this is wrong.

Please see the patch which I send you which gets this right.

Regards,

Hans

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