Re: [PATCH v2] mmc: fsl_esdhc_imx: use VENDORSPEC_FRC_SDCLK_ON when necessary

[Jaehoon Chung <jh80.chung@samsung.com>]

On 2/22/22 12:28, haibo.chen@nxp.com wrote:
> From: Haibo Chen <haibo.chen@nxp.com>
> 
> After commit f132aab40327 ("Revert "mmc: fsl_esdhc_imx: use
> VENDORSPEC_FRC_SDCLK_ON to control card clock output""), it
> involve issue in mmc_switch_voltage(), because of the special
> design of usdhc.
> 
> For FSL_USDHC, it do not implement VENDORSPEC_CKEN/PEREN/HCKEN/IPGEN,
> these are reserved bits(Though RM contain the definition of these bits,
> but actually internal IC logic do not implement, already confirm with
> IC team). Instead, use VENDORSPEC_FRC_SDCLK_ON to gate on/off the card
> clock output. Here is the definition of this bit in RM:
> 
> [8] FRC_SDCLK_ON
> Force CLK output active
> Do not set this bit to 1 unless it is necessary. Also, make sure that
> this bit is cleared when uSDHC’s clock is about to be changed (frequency
> change, clock source change, or delay chain tuning).
> 0b - CLK active or inactive is fully controlled by the hardware.
> 1b - Force CLK active
> 
> In default, the FRC_SDCLK_ON is 0. This means, when there is no command
> or data transfer on bus, hardware will gate off the card clock. But in
> some case, we need the card clock keep on. Take IO voltage 1.8v switch
> as example, after IO voltage change to 1.8v, spec require gate off the
> card clock for 5ms, and gate on the clock back, once detect the card
> clock on, then the card will draw the dat0 to high immediately. If there
> is not clock gate off/on behavior, some card will keep the dat0 to low
> level. This is the reason we fail in mmc_switch_voltage().
> 
> To fix this issue, and concern that this is only the fsl usdhc hardware
> design limitation, set the bit FRC_SDCLK_ON in the beginning of the
> wait_dat0() and clear it in the end. To make sure the 1.8v IO voltage
> switch process align with SD specification.
> 
> For standard tuning process, usdhc specification also require the card
> clock keep on, so also add these behavior in fsl_esdhc_execute_tuning().
> 
> Reviewed-by: Marek Vasut <marex@denx.de>
> Tested-by: Fabio Estevam <festevam@gmail.com>
> Signed-off-by: Haibo Chen <haibo.chen@nxp.com>

Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>

Best Regards,
Jaehoon Chung

> ---
>  drivers/mmc/fsl_esdhc_imx.c | 25 ++++++++++++++++++++++---
>  include/fsl_esdhc_imx.h     |  2 ++
>  2 files changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mmc/fsl_esdhc_imx.c b/drivers/mmc/fsl_esdhc_imx.c
> index 9299635f50..e0108144e7 100644
> --- a/drivers/mmc/fsl_esdhc_imx.c
> +++ b/drivers/mmc/fsl_esdhc_imx.c
> @@ -831,13 +831,16 @@ static int fsl_esdhc_execute_tuning(struct udevice *dev, uint32_t opcode)
>  	struct mmc *mmc = &plat->mmc;
>  	u32 irqstaten = esdhc_read32(&regs->irqstaten);
>  	u32 irqsigen = esdhc_read32(&regs->irqsigen);
> -	int i, ret = -ETIMEDOUT;
> -	u32 val, mixctrl;
> +	int i, err, ret = -ETIMEDOUT;
> +	u32 val, mixctrl, tmp;
>  
>  	/* clock tuning is not needed for upto 52MHz */
>  	if (mmc->clock <= 52000000)
>  		return 0;
>  
> +	/* make sure the card clock keep on */
> +	esdhc_setbits32(&regs->vendorspec, VENDORSPEC_FRC_SDCLK_ON);
> +
>  	/* This is readw/writew SDHCI_HOST_CONTROL2 when tuning */
>  	if (priv->flags & ESDHC_FLAG_STD_TUNING) {
>  		val = esdhc_read32(&regs->autoc12err);
> @@ -897,6 +900,12 @@ static int fsl_esdhc_execute_tuning(struct udevice *dev, uint32_t opcode)
>  
>  	esdhc_stop_tuning(mmc);
>  
> +	/* change to default setting, let host control the card clock */
> +	esdhc_clrbits32(&regs->vendorspec, VENDORSPEC_FRC_SDCLK_ON);
> +	err = readx_poll_timeout(esdhc_read32, &regs->prsstat, tmp, tmp & PRSSTAT_SDOFF, 100);
> +	if (err)
> +		dev_warn(dev, "card clock not gate off as expect.\n");
> +
>  	return ret;
>  }
>  #endif
> @@ -1555,14 +1564,24 @@ static int __maybe_unused fsl_esdhc_set_enhanced_strobe(struct udevice *dev)
>  static int fsl_esdhc_wait_dat0(struct udevice *dev, int state,
>  				int timeout_us)
>  {
> -	int ret;
> +	int ret, err;
>  	u32 tmp;
>  	struct fsl_esdhc_priv *priv = dev_get_priv(dev);
>  	struct fsl_esdhc *regs = priv->esdhc_regs;
>  
> +	/* make sure the card clock keep on */
> +	esdhc_setbits32(&regs->vendorspec, VENDORSPEC_FRC_SDCLK_ON);
> +
>  	ret = readx_poll_timeout(esdhc_read32, &regs->prsstat, tmp,
>  				!!(tmp & PRSSTAT_DAT0) == !!state,
>  				timeout_us);
> +
> +	/* change to default setting, let host control the card clock */
> +	esdhc_clrbits32(&regs->vendorspec, VENDORSPEC_FRC_SDCLK_ON);
> +	err = readx_poll_timeout(esdhc_read32, &regs->prsstat, tmp, tmp & PRSSTAT_SDOFF, 100);
> +	if (err)
> +		dev_warn(dev, "card clock not gate off as expect.\n");
> +
>  	return ret;
>  }
>  
> diff --git a/include/fsl_esdhc_imx.h b/include/fsl_esdhc_imx.h
> index 2153f29bef..b8efd2a166 100644
> --- a/include/fsl_esdhc_imx.h
> +++ b/include/fsl_esdhc_imx.h
> @@ -37,6 +37,7 @@
>  #define VENDORSPEC_HCKEN	0x00001000
>  #define VENDORSPEC_IPGEN	0x00000800
>  #define VENDORSPEC_INIT		0x20007809
> +#define VENDORSPEC_FRC_SDCLK_ON 0x00000100
>  
>  #define IRQSTAT			0x0002e030
>  #define IRQSTAT_DMAE		(0x10000000)
> @@ -94,6 +95,7 @@
>  #define PRSSTAT_CINS		(0x00010000)
>  #define PRSSTAT_BREN		(0x00000800)
>  #define PRSSTAT_BWEN		(0x00000400)
> +#define PRSSTAT_SDOFF		(0x00000080)
>  #define PRSSTAT_SDSTB		(0X00000008)
>  #define PRSSTAT_DLA		(0x00000004)
>  #define PRSSTAT_CICHB		(0x00000002)