linux-kernel - Re: [PATCH v2] mmc: dw_mmc: add hw

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Message-id: <568A089B.20109@samsung.com>
Date:	Mon, 04 Jan 2016 14:52:27 +0900
From:	Jaehoon Chung <jh80.chung@...sung.com>
To:	Shawn Lin <shawn.lin@...k-chips.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mmc: dw_mmc: add hw_reset support

Hi, Shawn.

On 01/04/2016 11:50 AM, Shawn Lin wrote:
> This patch implement hw_reset function for DesignWare
> MMC controller. By adding this feature, mmc blk can
> do some basic recovery.
> 
>>>From Synopsys DesignWare Cores Mobile Storage Host Databook
> (Section 7.4.4), we get the details:
> 1. Program CMD12 to end any transfer in process.
> 2. Wait for DTO, even if no response is sent back by the card.
> 3. Set the following resets:
> 	Software reset – BMOD[0] for IDMAC only
> 	DMA reset– CTRL[2]
> 	FIFO reset – CTRL[1] bits
> 4. Program the CARD_RESET register with a value of 0 for the bit
> corresponding to the card number; This can be done at any time when
> the card is connected to the controller. This programming asserts the
> RST_n signal and resets the card.
> 5. Wait for minimum of 1 μs or cclk_in period, which ever is greater
> 6. After a minimum of 1 μs, the application should program a value of
> 0 into the CARD_RESET register for the bit corresponding to the card
> number. This de-asserts the RST_n signal and takes the card out of reset.
> 7. The application can program a new CMD only after a minimum of 200 us
> after the de-assertion of the RST_n signal, as per the MMC 4.41 standard.
> 
> HW reset producer will be call in mmc_init_card before mmc_go_idle. At that
> time，dw mmc hasn't update clk for itself, so CMD12 is inappropriate and
> unnecessary. Moreover, if mmc device runs into broken states, DRTO or RTO
> generated by previous cmd w/ data will make mmc core issue stop already. Then
> it will retry again and again, issue stop and card status again until the
> cmd's retry number decrease to zero. That will finally trigger HW reset producer
> if we declare MMC_CAP_HW_RESET. So there's no need to do step 1 and 2 for the
> reasons we mentioned above.

Which IP version did you use? Could you share it..?
Did you know about CHIP RESET sequence?

> 
> This implementation can be easily tested by cutting off->On vmmc while doing data
> accessing in background to simulate that case. And dw_mmc can generate timeout
> interrupt and make mmc core trigger hw reset producer before re-init mmc card
> to recover itself.
> 
> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
> 
> ---
> 
> Changes in v2:
> - remove unecessary mb
> - reduce time cost for hw_reset
> - combine SDMMC_CTRL_DMA_RESET and SDMMC_CTRL_FIFO_RESET
> 
>  drivers/mmc/host/dw_mmc.c | 25 +++++++++++++++++++++++++
>  drivers/mmc/host/dw_mmc.h |  4 ++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 7128351..98e75fc 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -1477,6 +1477,30 @@ static int dw_mci_get_cd(struct mmc_host *mmc)
>  	return present;
>  }
>  
> +static void dw_mci_hw_reset(struct mmc_host *mmc)
> +{
> +	struct dw_mci_slot *slot = mmc_priv(mmc);
> +	struct dw_mci *host = slot->host;
> +
> +	if (host->use_dma == TRANS_MODE_IDMAC)
> +		dw_mci_idmac_reset(host);
> +
> +	if (!dw_mci_ctrl_reset(host, SDMMC_CTRL_DMA_RESET |
> +				     SDMMC_CTRL_FIFO_RESET))
> +		return;
> +
> +	/*
> +	 * According to eMMC spec, card reset procedure:
> +	 * tRstW >= 1us:   RST_n pulse width
> +	 * tRSCA >= 200us: RST_n to Command time
> +	 * tRSTH >= 1us:   RST_n high period
> +	 */
> +	 mci_writel(slot->host, RST_N, SDMMC_RST_HWRESET);

Even though we used only one slot, but it needs to control bit with slot->id.

Best Regards,
Jaehoon Chung

> +	 usleep_range(1, 2);
> +	 mci_writel(slot->host, RST_N, SDMMC_RST_HWACTIVE);
> +	 usleep_range(200, 300);
> +}
> +
>  static void dw_mci_init_card(struct mmc_host *mmc, struct mmc_card *card)
>  {
>  	struct dw_mci_slot *slot = mmc_priv(mmc);
> @@ -1563,6 +1587,7 @@ static const struct mmc_host_ops dw_mci_ops = {
>  	.set_ios		= dw_mci_set_ios,
>  	.get_ro			= dw_mci_get_ro,
>  	.get_cd			= dw_mci_get_cd,
> +	.hw_reset               = dw_mci_hw_reset,
>  	.enable_sdio_irq	= dw_mci_enable_sdio_irq,
>  	.execute_tuning		= dw_mci_execute_tuning,
>  	.card_busy		= dw_mci_card_busy,
> diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
> index f695b58..684ee34 100644
> --- a/drivers/mmc/host/dw_mmc.h
> +++ b/drivers/mmc/host/dw_mmc.h
> @@ -46,6 +46,7 @@
>  #define SDMMC_VERID		0x06c
>  #define SDMMC_HCON		0x070
>  #define SDMMC_UHS_REG		0x074
> +#define SDMMC_RST_N		0x078
>  #define SDMMC_BMOD		0x080
>  #define SDMMC_PLDMND		0x084
>  #define SDMMC_DBADDR		0x088
> @@ -169,6 +170,9 @@
>  #define SDMMC_IDMAC_ENABLE		BIT(7)
>  #define SDMMC_IDMAC_FB			BIT(1)
>  #define SDMMC_IDMAC_SWRESET		BIT(0)
> +/* H/W reset */
> +#define SDMMC_RST_HWACTIVE		0x1
> +#define SDMMC_RST_HWRESET		0x0
>  /* Version ID register define */
>  #define SDMMC_GET_VERID(x)		((x) & 0xFFFF)
>  /* Card read threshold */
> 

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