Re: [PATCH 2/3] scsi: ufs: Allow resetting the UFS device

[Alim Akhtar <alim.akhtar@samsung.com>]

Hi Marc
Thanks for coping me.

On 6/4/19 1:23 PM, Marc Gonzalez wrote:
> [ Shuffling the recipients list ]
> 
> On 04/06/2019 09:20, Bjorn Andersson wrote:
> 
>> Acquire the device-reset GPIO and toggle this to reset the UFS device
>> during initialization and host reset.
>>
>> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
>> ---
>>   drivers/scsi/ufs/ufshcd.c | 44 +++++++++++++++++++++++++++++++++++++++
>>   drivers/scsi/ufs/ufshcd.h |  4 ++++
>>   2 files changed, 48 insertions(+)
>>
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 8c1c551f2b42..951a0efee536 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -42,6 +42,7 @@
>>   #include <linux/nls.h>
>>   #include <linux/of.h>
>>   #include <linux/bitfield.h>
>> +#include <linux/gpio/consumer.h>
>>   #include "ufshcd.h"
>>   #include "ufs_quirks.h"
>>   #include "unipro.h"
>> @@ -6104,6 +6105,25 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
>>   	return err;
>>   }
>>   
>> +/**
>> + ufshcd_device_reset() - toggle the (optional) device reset line
>> + * @hba: per-adapter instance
>> + *
>> + * Toggles the (optional) reset line to reset the attached device.
>> + */
>> +static void ufshcd_device_reset(struct ufs_hba *hba)
>> +{
>> +	/*
>> +	 * The USB device shall detect reset pulses of 1us, sleep for 10us to
>> +	 * be on the safe side.
>> +	 */
>> +	gpiod_set_value_cansleep(hba->device_reset, 1);
>> +	usleep_range(10, 15);
>> +
>> +	gpiod_set_value_cansleep(hba->device_reset, 0);
>> +	usleep_range(10, 15);
>> +}
>> +
>>   /**
>>    * ufshcd_host_reset_and_restore - reset and restore host controller
>>    * @hba: per-adapter instance
>> @@ -6159,6 +6179,9 @@ static int ufshcd_reset_and_restore(struct ufs_hba *hba)
>>   	int retries = MAX_HOST_RESET_RETRIES;
>>   
>>   	do {
>> +		/* Reset the attached device */
>> +		ufshcd_device_reset(hba);
>> +
>>   		err = ufshcd_host_reset_and_restore(hba);
>>   	} while (err && --retries);
>>   
>> @@ -7355,6 +7378,18 @@ static void ufshcd_variant_hba_exit(struct ufs_hba *hba)
>>   	ufshcd_vops_exit(hba);
>>   }
>>   
>> +static int ufshcd_init_device_reset(struct ufs_hba *hba)
>> +{
>> +	hba->device_reset = devm_gpiod_get_optional(hba->dev, "device-reset",
>> +						    GPIOD_OUT_HIGH);
>> +	if (IS_ERR(hba->device_reset)) {
>> +		dev_err(hba->dev, "failed to acquire reset gpio: %ld\n",
>> +			PTR_ERR(hba->device_reset));
>> +	}
>> +
>> +	return PTR_ERR_OR_ZERO(hba->device_reset);
>> +}
>> +
>>   static int ufshcd_hba_init(struct ufs_hba *hba)
>>   {
>>   	int err;
>> @@ -7394,9 +7429,15 @@ static int ufshcd_hba_init(struct ufs_hba *hba)
>>   	if (err)
>>   		goto out_disable_vreg;
>>   
>> +	err = ufshcd_init_device_reset(hba);
>> +	if (err)
>> +		goto out_disable_variant;
>> +
>>   	hba->is_powered = true;
>>   	goto out;
>>   
>> +out_disable_variant:
>> +	ufshcd_vops_setup_regulators(hba, false);
>>   out_disable_vreg:
>>   	ufshcd_setup_vreg(hba, false);
>>   out_disable_clks:
>> @@ -8290,6 +8331,9 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
>>   		goto exit_gating;
>>   	}
>>   
>> +	/* Reset the attached device */
>> +	ufshcd_device_reset(hba);
>> +
>>   	/* Host controller enable */
>>   	err = ufshcd_hba_enable(hba);
>>   	if (err) {
>> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
>> index ecfa898b9ccc..d8be67742168 100644
>> --- a/drivers/scsi/ufs/ufshcd.h
>> +++ b/drivers/scsi/ufs/ufshcd.h
>> @@ -72,6 +72,8 @@
>>   #define UFSHCD "ufshcd"
>>   #define UFSHCD_DRIVER_VERSION "0.2"
>>   
>> +struct gpio_desc;
>> +
>>   struct ufs_hba;
>>   
>>   enum dev_cmd_type {
>> @@ -706,6 +708,8 @@ struct ufs_hba {
>>   
>>   	struct device		bsg_dev;
>>   	struct request_queue	*bsg_queue;
>> +
>> +	struct gpio_desc *device_reset;
>>   };
>>   
>>   /* Returns true if clocks can be gated. Otherwise false */
>>
> 
> Why is this needed on 845 and not on 8998?
> 
Not sure about MSM, but this is high implementation dependent, different 
SoC vendors implement device reset in different way, like one mentioned 
above in this patch, and in case of Samsung/exynos, HCI register control 
device reset. AFA ufs spec is concerns, it just mandate about connecting 
a active low signal to RST_n pin of the ufs device.
> On 8998 we already have:
> 
> 			resets = <&gcc GCC_UFS_BCR>;
> 			reset-names = "rst";
> 
> The above reset line gets wiggled/frobbed when appropriate.
> 
> (What's the difference between gpio and pinctrl? vs a reset "clock" as above)
> 
> ufshcd_device_reset_ctrl() vs ufshcd_init_device_reset()
> 
> Sounds like the nomenclature could be unified or clarified.
> 
> Regards.
> 
>