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Date:   Thu, 12 Dec 2019 06:01:43 +0000
From:   cang@codeaurora.org
To:     Bjorn Andersson <bjorn.andersson@linaro.org>
Cc:     asutoshd@codeaurora.org, nguyenb@codeaurora.org,
        rnayak@codeaurora.org, linux-scsi@vger.kernel.org,
        kernel-team@android.com, saravanak@google.com, salyzyn@google.com,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        Pedro Sousa <pedrom.sousa@synopsys.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Evan Green <evgreen@chromium.org>,
        Kishon Vijay Abraham I <kishon@ti.com>,
        Stephen Boyd <swboyd@chromium.org>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Bean Huo <beanhuo@micron.com>,
        Bart Van Assche <bvanassche@acm.org>,
        Venkat Gopalakrishnan <venkatg@codeaurora.org>,
        Tomas Winkler <tomas.winkler@intel.com>,
        Arnd Bergmann <arnd@arndb.de>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/3] scsi: ufs: Modulize ufs-bsg
In-Reply-To: <20191212045357.GA415177@yoga>
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On 2019-12-12 12:53, Bjorn Andersson wrote:
> On Wed 11 Dec 00:49 PST 2019, Can Guo wrote:
> 
>> In order to improve the flexibility of ufs-bsg, modulizing it is a 
>> good
>> choice. This change introduces tristate to ufs-bsg to allow users 
>> compile
>> it as an external module.
> 
> Can you please elaborate on what this "flexibility" is and why it's a
> good thing?
> 

ufs-bsg is a helpful gadget for debug/test purpose. But neither
disabling it nor enabling it is the best way on a commercialized
device. Disabling it means we cannot use it, while enabling it
by default will expose all the DEVM/UIC/TM interfaces to user space,
which is not "safe" on a commercialized device to let users play with 
it.
Making it a module can resolve this, because only vendors can install it
as they have the root permissions.

>> 
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> ---
>>  drivers/scsi/ufs/Kconfig   |  3 ++-
>>  drivers/scsi/ufs/Makefile  |  2 +-
>>  drivers/scsi/ufs/ufs_bsg.c | 49 
>> +++++++++++++++++++++++++++++++++++++++++++---
>>  drivers/scsi/ufs/ufs_bsg.h |  8 --------
>>  drivers/scsi/ufs/ufshcd.c  | 36 ++++++++++++++++++++++++++++++----
>>  drivers/scsi/ufs/ufshcd.h  |  7 ++++++-
>>  6 files changed, 87 insertions(+), 18 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/Kconfig b/drivers/scsi/ufs/Kconfig
>> index d14c224..72620ce 100644
>> --- a/drivers/scsi/ufs/Kconfig
>> +++ b/drivers/scsi/ufs/Kconfig
>> @@ -38,6 +38,7 @@ config SCSI_UFSHCD
>>  	select PM_DEVFREQ
>>  	select DEVFREQ_GOV_SIMPLE_ONDEMAND
>>  	select NLS
>> +	select BLK_DEV_BSGLIB
> 
> Why is this needed?
> 

Because ufshcd.c needs to call some funcs defined in bsg lib.

>>  	---help---
>>  	This selects the support for UFS devices in Linux, say Y and make
>>  	  sure that you know the name of your UFS host adapter (the card
>> @@ -143,7 +144,7 @@ config SCSI_UFS_TI_J721E
>>  	  If unsure, say N.
>> 
>>  config SCSI_UFS_BSG
>> -	bool "Universal Flash Storage BSG device node"
>> +	tristate "Universal Flash Storage BSG device node"
>>  	depends on SCSI_UFSHCD
>>  	select BLK_DEV_BSGLIB
>>  	help
>> diff --git a/drivers/scsi/ufs/Makefile b/drivers/scsi/ufs/Makefile
>> index 94c6c5d..904eff1 100644
>> --- a/drivers/scsi/ufs/Makefile
>> +++ b/drivers/scsi/ufs/Makefile
>> @@ -6,7 +6,7 @@ obj-$(CONFIG_SCSI_UFS_CDNS_PLATFORM) += cdns-pltfrm.o
>>  obj-$(CONFIG_SCSI_UFS_QCOM) += ufs-qcom.o
>>  obj-$(CONFIG_SCSI_UFSHCD) += ufshcd-core.o
>>  ufshcd-core-y				+= ufshcd.o ufs-sysfs.o
>> -ufshcd-core-$(CONFIG_SCSI_UFS_BSG)	+= ufs_bsg.o
>> +obj-$(CONFIG_SCSI_UFS_BSG)	+= ufs_bsg.o
>>  obj-$(CONFIG_SCSI_UFSHCD_PCI) += ufshcd-pci.o
>>  obj-$(CONFIG_SCSI_UFSHCD_PLATFORM) += ufshcd-pltfrm.o
>>  obj-$(CONFIG_SCSI_UFS_HISI) += ufs-hisi.o
>> diff --git a/drivers/scsi/ufs/ufs_bsg.c b/drivers/scsi/ufs/ufs_bsg.c
>> index 3a2e68f..302222f 100644
>> --- a/drivers/scsi/ufs/ufs_bsg.c
>> +++ b/drivers/scsi/ufs/ufs_bsg.c
>> @@ -164,13 +164,15 @@ static int ufs_bsg_request(struct bsg_job *job)
>>   */
>>  void ufs_bsg_remove(struct ufs_hba *hba)
>>  {
>> -	struct device *bsg_dev = &hba->bsg_dev;
>> +	struct device *bsg_dev = hba->bsg_dev;
>> 
>>  	if (!hba->bsg_queue)
>>  		return;
>> 
>>  	bsg_remove_queue(hba->bsg_queue);
>> 
>> +	hba->bsg_dev = NULL;
>> +	hba->bsg_queue = NULL;
>>  	device_del(bsg_dev);
>>  	put_device(bsg_dev);
>>  }
>> @@ -178,6 +180,7 @@ void ufs_bsg_remove(struct ufs_hba *hba)
>>  static inline void ufs_bsg_node_release(struct device *dev)
>>  {
>>  	put_device(dev->parent);
>> +	kfree(dev);
>>  }
>> 
>>  /**
>> @@ -186,14 +189,19 @@ static inline void ufs_bsg_node_release(struct 
>> device *dev)
>>   *
>>   * Called during initial loading of the driver, and before 
>> scsi_scan_host.
>>   */
>> -int ufs_bsg_probe(struct ufs_hba *hba)
>> +static int ufs_bsg_probe(struct ufs_hba *hba)
>>  {
>> -	struct device *bsg_dev = &hba->bsg_dev;
>> +	struct device *bsg_dev;
>>  	struct Scsi_Host *shost = hba->host;
>>  	struct device *parent = &shost->shost_gendev;
>>  	struct request_queue *q;
>>  	int ret;
>> 
>> +	bsg_dev = kzalloc(sizeof(*bsg_dev), GFP_KERNEL);
>> +	if (!bsg_dev)
>> +		return -ENOMEM;
>> +
>> +	hba->bsg_dev = bsg_dev;
>>  	device_initialize(bsg_dev);
>> 
>>  	bsg_dev->parent = get_device(parent);
>> @@ -217,6 +225,41 @@ int ufs_bsg_probe(struct ufs_hba *hba)
>> 
>>  out:
>>  	dev_err(bsg_dev, "fail to initialize a bsg dev %d\n", 
>> shost->host_no);
>> +	hba->bsg_dev = NULL;
>>  	put_device(bsg_dev);
>>  	return ret;
>>  }
>> +
>> +static int __init ufs_bsg_init(void)
>> +{
>> +	struct list_head *hba_list = NULL;
>> +	struct ufs_hba *hba;
>> +	int ret = 0;
>> +
>> +	ufshcd_get_hba_list_lock(&hba_list);
>> +	list_for_each_entry(hba, hba_list, list) {
>> +		ret = ufs_bsg_probe(hba);
>> +		if (ret)
>> +			break;
>> +	}
> 
> So what happens if I go CONFIG_SCSI_UFS_BSG=y and
> CONFIG_SCSI_UFS_QCOM=y?
> 
> Wouldn't that mean that ufs_bsg_init() is called before ufshcd_init()
> has added the controller to the list? And even in the even that they 
> are
> both =m, what happens if they are invoked in the "wrong" order?
> 

In the case that CONFIG_SCSI_UFS_BSG=y and CONFIG_SCSI_UFS_QCOM=y,
I give late_initcall_sync(ufs_bsg_init) to make sure ufs_bsg_init
is invoked only after platform driver is probed. I tested this 
combination.

In the case that both of them are "m", installing ufs-bsg before 
ufs-qcom
is installed would have no effect as ufs_hba_list is empty, which is 
expected.
And in real cases, as the UFS is the boot device, UFS driver will always
be probed during bootup.

>> +	ufshcd_put_hba_list_unlock();
>> +
>> +	return ret;
>> +}
>> +
>> +static void __exit ufs_bsg_exit(void)
>> +{
>> +	struct list_head *hba_list = NULL;
>> +	struct ufs_hba *hba;
>> +
>> +	ufshcd_get_hba_list_lock(&hba_list);
>> +	list_for_each_entry(hba, hba_list, list)
>> +		ufs_bsg_remove(hba);
>> +	ufshcd_put_hba_list_unlock();
>> +}
>> +
>> +late_initcall_sync(ufs_bsg_init);
>> +module_exit(ufs_bsg_exit);
>> +
>> +MODULE_ALIAS("ufs-bsg");
> 
> The purpose of MODULE_ALIAS() is to facilitate module autoloading, but
> as you probe the bsg device from the initcall of the bsg driver itself 
> I
> don't see how that would happen, and as such I don't think this alias
> has a purpose.
> 

Good point, will remove it.

>> +MODULE_LICENSE("GPL v2");
>> diff --git a/drivers/scsi/ufs/ufs_bsg.h b/drivers/scsi/ufs/ufs_bsg.h
>> index d099187..9d922c0 100644
>> --- a/drivers/scsi/ufs/ufs_bsg.h
>> +++ b/drivers/scsi/ufs/ufs_bsg.h
>> @@ -12,12 +12,4 @@
>>  #include "ufshcd.h"
>>  #include "ufs.h"
>> 
>> -#ifdef CONFIG_SCSI_UFS_BSG
>> -void ufs_bsg_remove(struct ufs_hba *hba);
>> -int ufs_bsg_probe(struct ufs_hba *hba);
>> -#else
>> -static inline void ufs_bsg_remove(struct ufs_hba *hba) {}
>> -static inline int ufs_bsg_probe(struct ufs_hba *hba) {return 0; }
>> -#endif
>> -
>>  #endif /* UFS_BSG_H */
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index a86b0fd..7a83a8f 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -108,6 +108,22 @@
>>  		       16, 4, buf, __len, false);                        \
>>  } while (0)
>> 
>> +static LIST_HEAD(ufs_hba_list);
>> +static DEFINE_MUTEX(ufs_hba_list_lock);
>> +
>> +void ufshcd_get_hba_list_lock(struct list_head **list)
>> +{
>> +	mutex_lock(&ufs_hba_list_lock);
>> +	*list = &ufs_hba_list;
>> +}
>> +EXPORT_SYMBOL_GPL(ufshcd_get_hba_list_lock);
>> +
>> +void ufshcd_put_hba_list_unlock(void)
>> +{
>> +	mutex_unlock(&ufs_hba_list_lock);
>> +}
>> +EXPORT_SYMBOL_GPL(ufshcd_put_hba_list_unlock);
>> +
>>  int ufshcd_dump_regs(struct ufs_hba *hba, size_t offset, size_t len,
>>  		     const char *prefix)
>>  {
>> @@ -2093,6 +2109,7 @@ int ufshcd_send_uic_cmd(struct ufs_hba *hba, 
>> struct uic_command *uic_cmd)
>>  	ufshcd_release(hba);
>>  	return ret;
>>  }
>> +EXPORT_SYMBOL_GPL(ufshcd_send_uic_cmd);
>> 
>>  /**
>>   * ufshcd_map_sg - Map scatter-gather list to prdt
>> @@ -6024,6 +6041,7 @@ int ufshcd_exec_raw_upiu_cmd(struct ufs_hba 
>> *hba,
>> 
>>  	return err;
>>  }
>> +EXPORT_SYMBOL_GPL(ufshcd_exec_raw_upiu_cmd);
>> 
>>  /**
>>   * ufshcd_eh_device_reset_handler - device reset handler registered 
>> to
>> @@ -7043,9 +7061,6 @@ static int ufshcd_probe_hba(struct ufs_hba *hba)
>>  			}
>>  			hba->clk_scaling.is_allowed = true;
>>  		}
>> -
>> -		ufs_bsg_probe(hba);
>> -
>>  		scsi_scan_host(hba->host);
>>  		pm_runtime_put_sync(hba->dev);
>>  	}
>> @@ -8248,7 +8263,16 @@ int ufshcd_shutdown(struct ufs_hba *hba)
>>   */
>>  void ufshcd_remove(struct ufs_hba *hba)
>>  {
>> -	ufs_bsg_remove(hba);
>> +	struct device *bsg_dev = hba->bsg_dev;
>> +
>> +	mutex_lock(&ufs_hba_list_lock);
>> +	list_del(&hba->list);
>> +	if (hba->bsg_queue) {
>> +		bsg_remove_queue(hba->bsg_queue);
>> +		device_del(bsg_dev);
> 
> Am I reading this correct in that you probe the bsg_dev form initcall
> and you delete it as the ufshcd instance is removed? That's not okay.
> 
> Regards,
> Bjorn
> 

If ufshcd is removed, its ufs-bsg, if exists, should also be removed.
Could you please enlighten me a better way to do this? Thanks.

Regards,
Can Guo.

>> +		put_device(bsg_dev);
>> +	}
>> +	mutex_unlock(&ufs_hba_list_lock);
>>  	ufs_sysfs_remove_nodes(hba->dev);
>>  	scsi_remove_host(hba->host);
>>  	scsi_host_put(hba->host);
>> @@ -8494,6 +8518,10 @@ int ufshcd_init(struct ufs_hba *hba, void 
>> __iomem *mmio_base, unsigned int irq)
>>  	async_schedule(ufshcd_async_scan, hba);
>>  	ufs_sysfs_add_nodes(hba->dev);
>> 
>> +	mutex_lock(&ufs_hba_list_lock);
>> +	list_add_tail(&hba->list, &ufs_hba_list);
>> +	mutex_unlock(&ufs_hba_list_lock);
>> +
>>  	return 0;
>> 
>>  out_remove_scsi_host:
>> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
>> index 2740f69..893debc 100644
>> --- a/drivers/scsi/ufs/ufshcd.h
>> +++ b/drivers/scsi/ufs/ufshcd.h
>> @@ -74,6 +74,9 @@
>> 
>>  struct ufs_hba;
>> 
>> +void ufshcd_get_hba_list_lock(struct list_head **list);
>> +void ufshcd_put_hba_list_unlock(void);
>> +
>>  enum dev_cmd_type {
>>  	DEV_CMD_TYPE_NOP		= 0x0,
>>  	DEV_CMD_TYPE_QUERY		= 0x1,
>> @@ -473,6 +476,7 @@ struct ufs_stats {
>> 
>>  /**
>>   * struct ufs_hba - per adapter private structure
>> + * @list: Anchored at ufs_hba_list
>>   * @mmio_base: UFSHCI base register address
>>   * @ucdl_base_addr: UFS Command Descriptor base address
>>   * @utrdl_base_addr: UTP Transfer Request Descriptor base address
>> @@ -527,6 +531,7 @@ struct ufs_stats {
>>   * @scsi_block_reqs_cnt: reference counting for scsi block requests
>>   */
>>  struct ufs_hba {
>> +	struct list_head list;
>>  	void __iomem *mmio_base;
>> 
>>  	/* Virtual memory reference */
>> @@ -734,7 +739,7 @@ struct ufs_hba {
>>  	struct ufs_desc_size desc_size;
>>  	atomic_t scsi_block_reqs_cnt;
>> 
>> -	struct device		bsg_dev;
>> +	struct device		*bsg_dev;
>>  	struct request_queue	*bsg_queue;
>>  };
>> 
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
>>