Re: [PATCH 4/5] fpga-mgr: separate getting/locking FPGA manager

From: Alan Tull <atull@kernel.org>
To: Moritz Fischer <mdf@kernel.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>, linux-fpga@vger.kernel.org
Subject: Re: [PATCH 4/5] fpga-mgr: separate getting/locking FPGA manager
Date: Thu, 6 Apr 2017 09:16:34 -0500	[thread overview]
Message-ID: <CANk1AXSR3osGe_wAYy_OE4oiw_ZvnuaX4Khxg5+KvxEa6kMWRw@mail.gmail.com> (raw)
In-Reply-To: <20170406040700.GA5981@tyrael.amer.corp.natinst.com>

On Wed, Apr 5, 2017 at 11:07 PM, Moritz Fischer <mdf@kernel.org> wrote:
> Hi Alan,
>
> minor nits, inline
>
> On Mon, Mar 13, 2017 at 04:53:32PM -0500, Alan Tull wrote:
>> Add fpga_mgr_lock/unlock functions that get a mutex for
>> exclusive use.
>>
>> of_fpga_mgr_get, fpga_mgr_get, and fpga_mgr_put no longer lock
>> the FPGA manager mutex.
>>
>> This makes it more straightforward to save a reference to
>> a FPGA manager and only attempting to lock it when programming
>> the FPGA.
>>
>> Signed-off-by: Alan Tull <atull@kernel.org>
>> ---
>>  drivers/fpga/fpga-mgr.c       | 44 +++++++++++++++++++++++++++++++------------
>>  drivers/fpga/fpga-region.c    | 13 +++++++++++--
>>  include/linux/fpga/fpga-mgr.h |  3 +++
>>  3 files changed, 46 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
>> index fde605b..f7c3648 100644
>> --- a/drivers/fpga/fpga-mgr.c
>> +++ b/drivers/fpga/fpga-mgr.c
>> @@ -376,28 +376,19 @@ ATTRIBUTE_GROUPS(fpga_mgr);
>>  struct fpga_manager *__fpga_mgr_get(struct device *dev)
>>  {
>>       struct fpga_manager *mgr;
>> -     int ret = -ENODEV;
>>
>>       mgr = to_fpga_manager(dev);
>>       if (!mgr)
>>               goto err_dev;
>>
>> -     /* Get exclusive use of fpga manager */
>> -     if (!mutex_trylock(&mgr->ref_mutex)) {
>> -             ret = -EBUSY;
>> -             goto err_dev;
>> -     }
>> -
>>       if (!try_module_get(dev->parent->driver->owner))
>> -             goto err_ll_mod;
>> +             goto err_dev;
>>
>>       return mgr;
>>
>> -err_ll_mod:
>> -     mutex_unlock(&mgr->ref_mutex);
>>  err_dev:
>>       put_device(dev);
>> -     return ERR_PTR(ret);
>> +     return ERR_PTR(-ENODEV);
>>  }
>>
>>  static int fpga_mgr_dev_match(struct device *dev, const void *data)
>> @@ -457,12 +448,41 @@ EXPORT_SYMBOL_GPL(of_fpga_mgr_get);
>>  void fpga_mgr_put(struct fpga_manager *mgr)
>>  {
>>       module_put(mgr->dev.parent->driver->owner);
>> -     mutex_unlock(&mgr->ref_mutex);
>>       put_device(&mgr->dev);
>>  }
>>  EXPORT_SYMBOL_GPL(fpga_mgr_put);
>>
>>  /**
>> + * fpga_mgr_lock - Lock FPGA manager for exclusive use
>> + * @mgr:     fpga manager
>> + *
>> + * Given a pointer to FPGA Manager (from fpga_mgr_get() or
>> + * of_fpga_mgr_put()) attempt to get the mutex.
>> + *
>> + * Return: 0 for success or -EBUSY
>> + */
>> +int fpga_mgr_lock(struct fpga_manager *mgr)
>> +{
>> +     if (!mutex_trylock(&mgr->ref_mutex)) {
>> +             dev_err(&mgr->dev, "FPGA manager is in use.\n");
>> +             return -EBUSY;
>> +     }
>> +
>> +     return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(fpga_mgr_lock);
>> +
>> +/**
>> + * fpga_mgr_unlock - Unlock FPGA manager
>> + * @mgr:     fpga manager
>> + */
>> +void fpga_mgr_unlock(struct fpga_manager *mgr)
>> +{
>> +     mutex_unlock(&mgr->ref_mutex);
>> +}
>> +EXPORT_SYMBOL_GPL(fpga_mgr_unlock);
>> +
>> +/**
>>   * fpga_mgr_register - register a low level fpga manager driver
>>   * @dev:     fpga manager device from pdev
>>   * @name:    fpga manager name
>> diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
>> index 294556e..815f178 100644
>> --- a/drivers/fpga/fpga-region.c
>> +++ b/drivers/fpga/fpga-region.c
>> @@ -125,7 +125,7 @@ static void fpga_region_put(struct fpga_region *region)
>>  }
>>
>>  /**
>> - * fpga_region_get_manager - get exclusive reference for FPGA manager
>> + * fpga_region_get_manager - get reference for FPGA manager
>>   * @region: FPGA region
>>   *
>>   * Get FPGA Manager from "fpga-mgr" property or from ancestor region.
>> @@ -245,10 +245,16 @@ static int fpga_region_program_fpga(struct fpga_region *region,
>>               return PTR_ERR(mgr);
>>       }
>>
>> +     ret = fpga_mgr_lock(mgr);
>> +     if (ret) {
>> +             pr_err("FPGA manager is busy\n");
>
> Am I missing something here, or could you use dev_err(&mgr->dev, ...)
> here?

Hi Moritz,

I agree, I can go though and look for pr_* print messages and
change them to dev_* in functions where I have the device.

Thanks!
Alan

>
>> +             goto err_put_mgr;
>> +     }
>> +
>>       ret = fpga_region_get_bridges(region, overlay);
>>       if (ret) {
>>               pr_err("failed to get fpga region bridges\n");
>
> Same here, (I know this is not part of this patch), maybe the above is
> for consistency reasons then. Maybe I'm missing something.
>> -             goto err_put_mgr;
>> +             goto err_unlock_mgr;
>>       }
>>
>>       ret = fpga_bridges_disable(&region->bridge_list);
>> @@ -269,6 +275,7 @@ static int fpga_region_program_fpga(struct fpga_region *region,
>>               goto err_put_br;
>>       }
>>
>> +     fpga_mgr_unlock(mgr);
>>       fpga_mgr_put(mgr);
>>       fpga_region_put(region);
>>
>> @@ -276,6 +283,8 @@ static int fpga_region_program_fpga(struct fpga_region *region,
>>
>>  err_put_br:
>>       fpga_bridges_put(&region->bridge_list);
>> +err_unlock_mgr:
>> +     fpga_mgr_unlock(mgr);
>>  err_put_mgr:
>>       fpga_mgr_put(mgr);
>>       fpga_region_put(region);
>> diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
>> index 45df05a..ae970ca 100644
>> --- a/include/linux/fpga/fpga-mgr.h
>> +++ b/include/linux/fpga/fpga-mgr.h
>> @@ -149,6 +149,9 @@ int fpga_mgr_firmware_load(struct fpga_manager *mgr,
>>
>>  int fpga_mgr_load(struct fpga_manager *mgr, struct fpga_image_info *info);
>>
>> +int fpga_mgr_lock(struct fpga_manager *mgr);
>> +void fpga_mgr_unlock(struct fpga_manager *mgr);
>> +
>>  struct fpga_manager *of_fpga_mgr_get(struct device_node *node);
>>
>>  struct fpga_manager *fpga_mgr_get(struct device *dev);
>> --
>> 2.7.4
>>
>> --
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>
> Cheers,
>
> Moritz