linux-kernel - Re: [PATCH V1 10/11] mmc: tegra: fix CQE resume sequence

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Date:   Fri, 8 Mar 2019 14:59:47 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        ulf.hansson@...aro.org, robh+dt@...nel.org, mark.rutland@....com,
        riteshh@...eaurora.org
Cc:     thierry.reding@...il.com, jonathanh@...dia.com, anrao@...dia.com,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH V1 10/11] mmc: tegra: fix CQE resume sequence

On 2/03/19 7:20 AM, Sowjanya Komatineni wrote:
> Tegra CQHCI/SDHCI design prevents write access to SDHCI block size
> register when CQE is enabled and unhalted.
> 
> CQHCI driver enabled CQE prior to invoking sdhci_cqe_enable which
> violates this Tegra specific host requirement.
> 
> This patch fixes this by configuring sdhci block registers prior
> to CQE unhalt.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
>  drivers/mmc/host/sdhci-tegra.c | 71 ++++++++++++++++++++++++++++++++++++------
>  1 file changed, 62 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 2b63626dc2fa..7063cfcdc590 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -1126,23 +1126,75 @@ static void tegra_sdhci_voltage_switch(struct sdhci_host *host)
>  		tegra_host->pad_calib_required = true;
>  }
>  
> +static void tegra_cqhci_writel(struct cqhci_host *cq_host, u32 val, int reg)
> +{
> +	struct mmc_host *mmc = cq_host->mmc;
> +	u8 ctrl;
> +	ktime_t timeout;
> +	bool timed_out;
> +
> +	/*
> +	 * During CQE resume/unhalt, CQHCI driver unhalts CQE prior to
> +	 * cqhci_host_ops enable where SDHCI DMA and BLOCK_SIZE registers need
> +	 * to be re-configured.
> +	 * Tegra CQHCI/SDHCI prevents write access to block size register when
> +	 * CQE is unhalted. So handling CQE resume sequence here to configure
> +	 * SDHCI block registers prior to exiting CQE halt state.
> +	 */
> +	if (reg == CQHCI_CTL && !(val & CQHCI_HALT) &&
> +	    cqhci_readl(cq_host, CQHCI_CTL) & CQHCI_HALT) {
> +		sdhci_cqe_enable(mmc);
> +		writel(val, cq_host->mmio + reg);
> +		timeout = ktime_add_us(ktime_get(), 50);
> +		while (1) {
> +			timed_out = ktime_compare(ktime_get(), timeout) > 0;
> +			ctrl = cqhci_readl(cq_host, CQHCI_CTL);
> +			if (!(ctrl & CQHCI_HALT) || timed_out)
> +				break;
> +		}
> +		/*
> +		 * CQE usually resumes very quick, but incase if Tegra CQE
> +		 * doesn't resume retry unhalt.
> +		 */
> +		if (timed_out)
> +			writel(val, cq_host->mmio + reg);
> +	} else {
> +		writel(val, cq_host->mmio + reg);
> +	}
> +}
> +
>  static void sdhci_tegra_cqe_enable(struct mmc_host *mmc)
>  {
>  	struct cqhci_host *cq_host = mmc->cqe_private;
> -	u32 cqcfg = 0;
> +	u32 val;
>  
>  	/*
> -	 * Tegra SDMMC Controller design prevents write access to BLOCK_COUNT
> -	 * registers when CQE is enabled.
> +	 * Tegra CQHCI/SDMMC design prevents write access to sdhci block size
> +	 * register when CQE is enabled and unhalted.
> +	 * CQHCI driver enables CQE prior to activation, so disable CQE before
> +	 * programming block size in sdhci controller and enable it back.
>  	 */
> -	cqcfg = cqhci_readl(cq_host, CQHCI_CFG);
> -	if (cqcfg & CQHCI_ENABLE)
> -		cqhci_writel(cq_host, (cqcfg & ~CQHCI_ENABLE), CQHCI_CFG);
> +	if (!cq_host->activated) {
> +		val = cqhci_readl(cq_host, CQHCI_CFG);
> +		if (val & CQHCI_ENABLE)
> +			cqhci_writel(cq_host, (val & ~CQHCI_ENABLE),
> +				     CQHCI_CFG);
> +		sdhci_cqe_enable(mmc);
> +		if (val & CQHCI_ENABLE)
> +			cqhci_writel(cq_host, val, CQHCI_CFG);
> +	}
>  
> -	sdhci_cqe_enable(mmc);
> +	/*
> +	 * CMD CRC errors are seen sometimes with some eMMC devices when status
> +	 * command is sent during transfer of last data block which is the
> +	 * default case as send status command block counter (CBC) is 1.
> +	 * So changing send status command block counter (CBC) to 0 to allow
> +	 * send status command only when the data lines are idle.
> +	 */
> +	val = cqhci_readl(cq_host, CQHCI_SSC1);
> +	val &= ~CQHCI_SSC1_CBC_MASK;
> +	cqhci_writel(cq_host, val, CQHCI_SSC1);
>  
> -	if (cqcfg & CQHCI_ENABLE)
> -		cqhci_writel(cq_host, cqcfg, CQHCI_CFG);
>  }
>  
>  static void sdhci_tegra_dumpregs(struct mmc_host *mmc)
> @@ -1167,6 +1219,7 @@ static const struct cqhci_host_ops sdhci_tegra_cqhci_ops = {
>  	.enable	= sdhci_tegra_cqe_enable,
>  	.disable = sdhci_cqe_disable,
>  	.dumpregs = sdhci_tegra_dumpregs,
> +	.write_l    = tegra_cqhci_writel,
>  };
>  
>  static const struct sdhci_ops tegra_sdhci_ops = {
>