linux-kernel - Re: [PATCH v4 6/6] mmc: sdhci-esdhc-imx: set back the burst_length

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Date:	Fri, 7 Aug 2015 15:50:51 +0800
From:	Dong Aisheng <aisheng.dong@...escale.com>
To:	Haibo Chen <haibo.chen@...escale.com>
CC:	<robh+dt@...nel.org>, <pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<shawnguo@...nel.org>, <kernel@...gutronix.de>,
	<linux@....linux.org.uk>, <ulf.hansson@...aro.org>,
	<johan.derycke@...co.com>, <mkl@...gutronix.de>,
	<fabio.estevam@...escale.com>, <b29396@...escale.com>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-mmc@...r.kernel.org>
Subject: Re: [PATCH v4 6/6] mmc: sdhci-esdhc-imx: set back the
 burst_length_enable bit to 1

On Wed, Aug 05, 2015 at 06:38:42PM +0800, Haibo Chen wrote:
> Currently we find that if a usdhc is choosed to boot system, then ROM
> code will set the burst length enable bit of this usdhc as 0.
> 
> This will make performance drop a lot if this usdhc's burst length is
> configed. So this patch set back the burst_length_enable bit as 1,
> which is the default value, and means burst length is enabled for INCR.
> 

This patch should be put before patch 5 to avoid function break, right?
[PATCH v4 5/6] mmc: sdhci-esdhc-imx: change default watermark level and burst length

Other than that, this patch looks good to me.

Regards
Dong Aisheng

> Signed-off-by: Haibo Chen <haibo.chen@...escale.com>
> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index 97aa944..3334762 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -32,6 +32,7 @@
>  #include "sdhci-esdhc.h"
>  
>  #define	ESDHC_CTRL_D3CD			0x08
> +#define ESDHC_BURST_LEN_EN_INCR		(1 << 27)
>  /* VENDOR SPEC register */
>  #define ESDHC_VENDOR_SPEC		0xc0
>  #define  ESDHC_VENDOR_SPEC_SDIO_QUIRK	(1 << 1)
> @@ -1165,6 +1166,21 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev)
>  		host->quirks2 |= SDHCI_QUIRK2_PRESET_VALUE_BROKEN;
>  		host->mmc->caps |= MMC_CAP_1_8V_DDR;
>  
> +		/*
> +		 * ROM code will change the bit burst_length_enable setting
> +		 * to zero if this usdhc is choosed to boot system. Change
> +		 * it back here, otherwise it will impact the performance a
> +		 * lot. This bit is used to enable/disable the burst length
> +		 * for the external AHB2AXI bridge, it's usefully especially
> +		 * for INCR transfer because without burst length indicator,
> +		 * the AHB2AXI bridge does not know the burst length in
> +		 * advance. And without burst length indicator, AHB INCR
> +		 * transfer can only be converted to singles on the AXI side.
> +		 */
> +		writel(readl(host->ioaddr + SDHCI_HOST_CONTROL)
> +			| ESDHC_BURST_LEN_EN_INCR,
> +			host->ioaddr + SDHCI_HOST_CONTROL);
> +
>  		if (!(imx_data->socdata->flags & ESDHC_FLAG_HS200))
>  			host->quirks2 |= SDHCI_QUIRK2_BROKEN_HS200;
>  
> -- 
> 1.9.1
> 
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