Re: [PATCH 1/2] mmc: dw_mmc-exynos: add support for controlling emmc reset pin

[Tobias Jakobi <liquid.acid-hi6Y0CQ0nG0@public.gmane.org>]

Hello!

Jaehoon Chung wrote:
> mmc core supported to hw_reset function.
> So i think we can use it. It's called at only initial time to clear the previous status.
> But i think it can be called at reboot time. (it needs to implement codes.)
> how about?
I don't think that's going the work. The problem here is that depending
on the board configuration, the eMMC might carry the bootloader. If the
eMMC subsystem is not properly reset _during_ reboot, the board won't
even start since no bootloader is found. So we don't even reach the
point where the kernel does anything.


With best wishes,
Tobias



> 
> Best Regards,
> Jaehoon Chung
> 
>>
>> Signed-off-by: Marek Szyprowski <m.szyprowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
>> ---
>>  .../devicetree/bindings/mmc/exynos-dw-mshc.txt     |  6 +++
>>  drivers/mmc/host/dw_mmc-exynos.c                   | 43 +++++++++++++++++++++-
>>  2 files changed, 48 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt
>> index ee4fc0576c7d..fc53d335e7db 100644
>> --- a/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt
>> +++ b/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt
>> @@ -50,6 +50,12 @@ Required Properties:
>>        - if CIU clock divider value is 0 (that is divide by 1), both tx and rx
>>          phase shift clocks should be 0.
>>  
>> +Optional properties:
>> +
>> +* dw-mshc-reset-gpios: optional property specifying gpio for the eMMC nreset
>> +  line, it will be triggered on system reboot to properly reset eMMC card for
>> +  next system boot.
>> +
>>  Required properties for a slot (Deprecated - Recommend to use one slot per host):
>>  
>>  * gpios: specifies a list of gpios used for command, clock and data bus. The
>> diff --git a/drivers/mmc/host/dw_mmc-exynos.c b/drivers/mmc/host/dw_mmc-exynos.c
>> index 509365cb22c6..2add5a93859d 100644
>> --- a/drivers/mmc/host/dw_mmc-exynos.c
>> +++ b/drivers/mmc/host/dw_mmc-exynos.c
>> @@ -12,12 +12,14 @@
>>  #include <linux/module.h>
>>  #include <linux/platform_device.h>
>>  #include <linux/clk.h>
>> +#include <linux/delay.h>
>>  #include <linux/mmc/host.h>
>>  #include <linux/mmc/dw_mmc.h>
>>  #include <linux/mmc/mmc.h>
>>  #include <linux/of.h>
>>  #include <linux/of_gpio.h>
>>  #include <linux/slab.h>
>> +#include <linux/reboot.h>
>>  
>>  #include "dw_mmc.h"
>>  #include "dw_mmc-pltfm.h"
>> @@ -77,8 +79,23 @@ struct dw_mci_exynos_priv_data {
>>  	u32				sdr_timing;
>>  	u32				ddr_timing;
>>  	u32				cur_speed;
>> +	struct gpio_desc 		*reset_gpio;
>> +	struct notifier_block		reset_nb;
>>  };
>>  
>> +static int dw_mci_restart_handler(struct notifier_block *this,
>> +				  unsigned long mode, void *cmd)
>> +{
>> +	struct dw_mci_exynos_priv_data *data;
>> +	data = container_of(this, struct dw_mci_exynos_priv_data, reset_nb);
>> +
>> +	gpiod_direction_output(data->reset_gpio, 0);
>> +	mdelay(150);
>> +	gpiod_direction_output(data->reset_gpio, 1);
>> +
>> +	return NOTIFY_DONE;
>> +}
>> +
>>  static struct dw_mci_exynos_compatible {
>>  	char				*compatible;
>>  	enum dw_mci_exynos_type		ctrl_type;
>> @@ -295,7 +312,20 @@ static int dw_mci_exynos_parse_dt(struct dw_mci *host)
>>  		return ret;
>>  
>>  	priv->ddr_timing = SDMMC_CLKSEL_TIMING(timing[0], timing[1], div);
>> +
>> +	priv->reset_gpio = devm_gpiod_get_optional(host->dev,
>> +						   "samsung,dw-mshc-reset",
>> +						   GPIOD_OUT_HIGH);
>> +	if (!IS_ERR_OR_NULL(priv->reset_gpio)) {
>> +		priv->reset_nb.notifier_call = dw_mci_restart_handler;
>> +		priv->reset_nb.priority = 255;
>> +		ret = register_restart_handler(&priv->reset_nb);
>> +		if (ret)
>> +			dev_err(host->dev, "cannot register restart handler\n");
>> +	}
>> +
>>  	host->priv = priv;
>> +
>>  	return 0;
>>  }
>>  
>> @@ -490,6 +520,17 @@ static int dw_mci_exynos_probe(struct platform_device *pdev)
>>  	return dw_mci_pltfm_register(pdev, drv_data);
>>  }
>>  
>> +static int dw_mci_exynos_remove(struct platform_device *pdev)
>> +{
>> +	struct dw_mci *host = platform_get_drvdata(pdev);
>> +	struct dw_mci_exynos_priv_data *priv = host->priv;
>> +
>> +	if (priv->reset_gpio)
>> +		unregister_restart_handler(&priv->reset_nb);
>> +
>> +	return dw_mci_pltfm_remove(pdev);
>> +}
>> +
>>  static const struct dev_pm_ops dw_mci_exynos_pmops = {
>>  	SET_SYSTEM_SLEEP_PM_OPS(dw_mci_exynos_suspend, dw_mci_exynos_resume)
>>  	.resume_noirq = dw_mci_exynos_resume_noirq,
>> @@ -499,7 +540,7 @@ static const struct dev_pm_ops dw_mci_exynos_pmops = {
>>  
>>  static struct platform_driver dw_mci_exynos_pltfm_driver = {
>>  	.probe		= dw_mci_exynos_probe,
>> -	.remove		= __exit_p(dw_mci_pltfm_remove),
>> +	.remove		= dw_mci_exynos_remove,
>>  	.driver		= {
>>  		.name		= "dwmmc_exynos",
>>  		.of_match_table	= dw_mci_exynos_match,
>>
> 
> 

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