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Message-ID: <e4f16bcd11db29869c08f920d2bd9480fcdc076d.camel@pengutronix.de>
Subject: Re: [PATCH v6 17/17] mmc: sdhci-cadence: Support mmc hardware reset
From:   Philipp Zabel <p.zabel@pengutronix.de>
To:     Brad Larson <brad@pensando.io>,
        linux-arm-kernel@lists.infradead.org
Cc:     linux-kernel@vger.kernel.org, linux-mmc@vger.kernel.org,
        adrian.hunter@intel.com, alcooperx@gmail.com,
        andy.shevchenko@gmail.com, arnd@arndb.de, blarson@amd.com,
        brijeshkumar.singh@amd.com, catalin.marinas@arm.com,
        gsomlo@gmail.com, gerg@linux-m68k.org, krzk@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, lee.jones@linaro.org,
        broonie@kernel.org, yamada.masahiro@socionext.com,
        piotrs@cadence.com, p.yadav@ti.com, rdunlap@infradead.org,
        robh+dt@kernel.org, samuel@sholland.org, fancer.lancer@gmail.com,
        suravee.suthikulpanit@amd.com, thomas.lendacky@amd.com,
        ulf.hansson@linaro.org, will@kernel.org, devicetree@vger.kernel.org
Date:   Mon, 22 Aug 2022 09:03:22 +0200
In-Reply-To: <20220820195750.70861-18-brad@pensando.io>
References: <20220820195750.70861-1-brad@pensando.io>
         <20220820195750.70861-18-brad@pensando.io>
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Hi Brad,

On Sa, 2022-08-20 at 12:57 -0700, Brad Larson wrote:
[...]
> +static void sdhci_mmc_hw_reset(struct mmc_host *mmc)
> +{
> +	struct sdhci_host *host = mmc_priv(mmc);
> +	struct sdhci_cdns_priv *priv = sdhci_cdns_priv(host);
> +
> +	dev_info(mmc_dev(host->mmc), "emmc hardware reset\n");
> +
> +	reset_control_assert(priv->rst_hw);
> +	/* For eMMC, minimum is 1us but give it 9us for good measure */
> +	udelay(9);

At a glance, this seems excessive. Is there a reason 9 us is better
than, say, 2 or 3?

[...]
> @@ -520,6 +538,17 @@ static int sdhci_cdns_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto free;
>  
> 
> 
> 
> +	if (host->mmc->caps & MMC_CAP_HW_RESET) {
> +		priv->rst_hw = devm_reset_control_get_optional_exclusive(dev, "hw");

This should be described in cdns,sdhci.yaml first.

regards
Philipp