On 19.08.2016 17:00, Thierry Reding wrote:
> From: Thierry Reding <treding@xxxxxxxxxx>
>
> The device tree binding for the SDHCI controller found on Tegra SoCs
> specifies that a reset control can be provided by the device tree. No
> code was ever added to support the module reset, which can cause the
> driver to try and access registers from a module that's in reset. On
> most Tegra SoC generations doing so would cause a hang.
>
> Note that it's unlikely to see this happen because on most platforms
> these resets will have been deasserted by the bootloader. However the
> portability can be improved by making sure the driver deasserts the
> reset before accessing any registers.
>
> Since resets are synchronous on Tegra SoCs, the platform driver needs
> to implement a custom ->remove() callback now to make sure the clock
> is disabled after the reset is asserted.
>
> Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
> ---
> drivers/mmc/host/sdhci-tegra.c | 38 +++++++++++++++++++++++++++++++++++++-
> 1 file changed, 37 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 1e93dc4e303e..4c29a64721aa 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -21,6 +21,7 @@
> #include <linux/io.h>
> #include <linux/of.h>
> #include <linux/of_device.h>
> +#include <linux/reset.h>
> #include <linux/mmc/card.h>
> #include <linux/mmc/host.h>
> #include <linux/mmc/mmc.h>
> @@ -65,6 +66,8 @@ struct sdhci_tegra {
> struct gpio_desc *power_gpio;
> bool ddr_signaling;
> bool pad_calib_required;
> +
> + struct reset_control *rst;
> };
>
> static u16 tegra_sdhci_readw(struct sdhci_host *host, int reg)
> @@ -464,6 +467,16 @@ static int sdhci_tegra_probe(struct platform_device *pdev)
> clk_prepare_enable(clk);
> pltfm_host->clk = clk;
>
> + tegra_host->rst = devm_reset_control_get(&pdev->dev, "sdhci");
> + if (IS_ERR(tegra_host->rst)) {
> + rc = PTR_ERR(tegra_host->rst);
> + dev_err(&pdev->dev, "failed to get reset control: %d\n", rc);
> + goto err_clk_get;
> + }
> +
> + reset_control_deassert(tegra_host->rst);
Why just not to do a proper reset here? You won't need a custom .remove then.
> + usleep_range(2000, 4000);
> +
Is this sleep after deassertion really needed?
> rc = sdhci_add_host(host);
> if (rc)
> goto err_add_host;
> @@ -479,6 +492,29 @@ err_parse_dt:
> return rc;
> }
>
> +static int sdhci_tegra_remove(struct platform_device *pdev)
> +{
> + struct sdhci_host *host = platform_get_drvdata(pdev);
> + struct sdhci_pltfm_host *platform = sdhci_priv(host);
> + struct sdhci_tegra *tegra = sdhci_pltfm_priv(platform);
> + int dead = 0;
> + u32 value;
> +
> + value = readl(host->ioaddr + SDHCI_INT_STATUS);
> + if (value == 0xffffffff)
> + dead = 1;
> +
> + sdhci_remove_host(host, dead);
> +
> + reset_control_assert(tegra->rst);
> + usleep_range(2000, 4000);
> + clk_disable_unprepare(platform->clk);
> +
> + sdhci_pltfm_free(pdev);
> +
> + return 0;
> +}
> +
> static struct platform_driver sdhci_tegra_driver = {
> .driver = {
> .name = "sdhci-tegra",
> @@ -486,7 +522,7 @@ static struct platform_driver sdhci_tegra_driver = {
> .pm = &sdhci_pltfm_pmops,
> },
> .probe = sdhci_tegra_probe,
> - .remove = sdhci_pltfm_unregister,
> + .remove = sdhci_tegra_remove,
> };
>
> module_platform_driver(sdhci_tegra_driver);
>
--
Dmitry
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