Date:	Mon, 4 Jan 2016 15:24:09 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Jaehoon Chung <jh80.chung@...sung.com>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>, shawn.lin@...k-chips.com,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mmc: dw_mmc: add hw_reset support

On 2016/1/4 13:52, Jaehoon Chung wrote:
> 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?
>

My dw_mmc IP version is 270a（0x5342270a from VERID register).
Do you mean "emmc chip hardware reset sequence"?
 From JESD84-B51 spec(section 6.15.10),

host pull down reset pin for at least 1us, and pull high it.
then emmc device will detect it as a IO interrupt to enter internal 
reset flow. Host should not issue CMD1 within 200us, which means emmc 
device MUST finish internal reset flow within 200us.

>>
>> 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.
>

yep, got it.

> 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 */
>>
>
>
>
>


-- 
Best Regards
Shawn Lin

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