linux-kernel - Re: [PATCHv2 3/3] fpga manager: Adding FPGA Manager support for Xilinx Zynq 7000

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Date:	Mon, 19 Oct 2015 09:28:13 -0700
From:	Moritz Fischer <moritz.fischer@...us.com>
To:	Josh Cartwright <joshc@...com>
Cc:	Michal Simek <michal.simek@...inx.com>,
	Rob Herring <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Sören Brinkmann <soren.brinkmann@...inx.com>,
	Russell King <linux@....linux.org.uk>,
	Alan Tull <atull@...nsource.altera.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	devicetree@...r.kernel.org,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 3/3] fpga manager: Adding FPGA Manager support for
 Xilinx Zynq 7000

On Sun, Oct 18, 2015 at 11:02 AM, Josh Cartwright <joshc@...com> wrote:
> Hey Moritz-
>
> On Fri, Oct 16, 2015 at 03:42:30PM -0700, Moritz Fischer wrote:
>> This commit adds FPGA Manager support for the Xilinx Zynq chip.
>> The code borrows some from the xdevcfg driver in Xilinx'
>> vendor tree.
>>
>> Signed-off-by: Moritz Fischer <moritz.fischer@...us.com>
>> ---
>>
>> v2:
>>  - Replaced locking error flag and broken completion with irq masking
>>    and changed completion handling
>>  - Dealing with timeout cases
>>  - Reworked clock handling
>>  - Moved initialization from probe() to write_init()
>>  - Fixed return value of devm_request_irq() check to check for non-zero
>>  - Alphabetized includes ;-)
>>  - Changed some of the comments, to better explain what's happening
> [..]
>> +static int zynq_fpga_probe(struct platform_device *pdev)
>> +{
> [..]
>> +     priv->clk = devm_clk_get(dev, "ref_clk");
>> +     if (IS_ERR(priv->clk)) {
>> +             dev_err(dev, "input clock not found");
>> +             return PTR_ERR(priv->clk);
>> +     }
>> +
>> +     err = clk_prepare_enable(priv->clk);
>> +     if (err) {
>> +             dev_err(dev, "unable to enable clock");
>> +             return err;
>> +     }
>
> prepare_cnt = 1, enable_cnt = 1
>
>> +
>> +     /* unlock the device */
>> +     zynq_fpga_write(priv, UNLOCK_OFFSET, UNLOCK_MASK);
>> +
>> +     clk_disable(priv->clk);
>
> prepare_cnt = 1, enable_cnt = 0
>> +
>> +     err = fpga_mgr_register(dev, "Xilinx Zynq FPGA Manager",
>> +                             &zynq_fpga_ops, priv);
>> +     if (err) {
>> +             dev_err(dev, "unable to register FPGA manager");
>> +             clk_disable_unprepare(priv->clk);
>
> prepare_cnt = 0, enable_cnt = -1 /* OOPS! */
>
> Clock management is still wonky.  I think you only want clk_unprepare here.
>
>> +             return err;
>> +     }
>> +
>
> Assuming all goes well, you'll be leaving probe() with:
>
> prepare_cnt = 1, enable_cnt = 0.
>
>> +     return 0;
>> +}
>> +
>> +static int zynq_fpga_remove(struct platform_device *pdev)
>> +{
>> +     struct zynq_fpga_priv *priv;
>> +
>> +     fpga_mgr_unregister(&pdev->dev);
>> +
>> +     priv = platform_get_drvdata(pdev);
>> +
>> +     clk_disable_unprepare(priv->clk);
>
> Which means, symmetrically, you'll only want this to be a clk_unprepare().
>
>   Josh

Greg had already queued the v2 this weekend (which caught me by
suprise). I tried to figure out if it's possible to send a v3,
but he said to send follow up patches as he can't rebase the branch he
merged it into.
I will have access to hardware this afternoon, and send out follow up
patches to fix the unbalanced clock handling.

Cheers,

Moritz
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