Date:   Fri, 17 Feb 2017 15:55:37 -0600
From:   Alan Tull <delicious.quinoa@...il.com>
To:     "Li, Yi" <yi1.li@...ux.intel.com>
Cc:     Moritz Fischer <moritz.fischer@...us.com>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-fpga@...r.kernel.org
Subject: Re: [RFC 4/8] doc: fpga-mgr: separate getting/locking FPGA manager

On Fri, Feb 17, 2017 at 11:14 AM, Li, Yi <yi1.li@...ux.intel.com> wrote:
> hi Alan
>
>
> On 2/15/2017 10:14 AM, Alan Tull wrote:
>>
>> Document that getting a reference to a FPGA Manager has been
>> separated from locking the FPGA Mangager for use.
>>
>> fpga_mgr_lock/unlock functions get/release mutex.
>>
>> of_fpga_mgr_get, fpga_mgr_get, and fpga_mgr_put no longer lock
>> the FPGA manager mutex.
>>
>> This makes it more straigtforward to save a reference to
>> a FPGA manager and only attempting to lock it when programming
>> the FPGA.
>
>
> New to the FPGA world, but I like the idea of shorter lock. Separating the
> lock from fpga_mgr_get will give underline FPGA device drivers more
> flexibility to acquire the mgr pointer.
> One newbie question, since the underline FPGA device driver does the
> fpga_mgr_register during probe, each manager instance belongs to that FPGA
> device only. What's the use to keep tracking the usage reference with
> fpga_mgr_put/get function, or is it enough to increase/decrease dev
> reference count in fpga_mgr_register/unregister function?

Hi Yi,

That's a good though but the code that creates the fpga mgr device might not be
the code that needs to hold a reference to it.  The device tree
implementation is an
example of this.  The fpga mgr devices are created completely
separately from the
fpga regions.

Alan

>
> Thanks,
> Yi
>
>>
>> Signed-off-by: Alan Tull <atull@...nel.org>
>> ---
>>   Documentation/fpga/fpga-mgr.txt | 19 ++++++++++++++++++-
>>   1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/fpga/fpga-mgr.txt
>> b/Documentation/fpga/fpga-mgr.txt
>> index 78f197f..06d5d5b 100644
>> --- a/Documentation/fpga/fpga-mgr.txt
>> +++ b/Documentation/fpga/fpga-mgr.txt
>> @@ -53,13 +53,26 @@ To get/put a reference to a FPGA manager:
>>         struct fpga_manager *of_fpga_mgr_get(struct device_node *node);
>>         struct fpga_manager *fpga_mgr_get(struct device *dev);
>>   -Given a DT node or device, get an exclusive reference to a FPGA
>> manager.
>> +Given a DT node or device, get an reference to a FPGA manager.  Pointer
>> +can be saved until you are ready to program the FPGA.
>>         void fpga_mgr_put(struct fpga_manager *mgr);
>>     Release the reference.
>>     +To get exclusive control of a FPGA manager:
>> +-------------------------------------------
>> +
>> +       int fpga_mgr_lock(struct fpga_magager *mgr);
>> +
>> +Call fpga_mgr_lock and verify that it returns 0 before attempting to
>> +program the FPGA.
>> +
>> +       void fpga_mgr_unlock(struct fpga_magager *mgr);
>> +
>> +Call fpga_mgr_unlock when done programming the FPGA.
>> +
>>   To register or unregister the low level FPGA-specific driver:
>>   -------------------------------------------------------------
>>   @@ -95,11 +108,13 @@ int ret;
>>     /* Get exclusive control of FPGA manager */
>>   struct fpga_manager *mgr = of_fpga_mgr_get(mgr_node);
>> +ret = fpga_mgr_lock(mgr);
>>     /* Load the buffer to the FPGA */
>>   ret = fpga_mgr_buf_load(mgr, &info, buf, count);
>>     /* Release the FPGA manager */
>> +fpga_mgr_unlock(mgr);
>>   fpga_mgr_put(mgr);
>>     @@ -124,11 +139,13 @@ int ret;
>>     /* Get exclusive control of FPGA manager */
>>   struct fpga_manager *mgr = of_fpga_mgr_get(mgr_node);
>> +ret = fpga_mgr_lock(mgr);
>>     /* Get the firmware image (path) and load it to the FPGA */
>>   ret = fpga_mgr_firmware_load(mgr, &info, path);
>>     /* Release the FPGA manager */
>> +fpga_mgr_unlock(mgr);
>>   fpga_mgr_put(mgr);
>>
>
>

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