linux-kernel - Re: [PATCH v2] fpga: zynq-fpga: Ensure proper xCAP interface switch

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Date:   Sun, 4 Jun 2023 01:27:21 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     Nava kishore Manne <nava.kishore.manne@....com>
Cc:     mdf@...nel.org, hao.wu@...el.com, trix@...hat.com,
        michal.simek@....com, linux-fpga@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Alfonso Rodriguez <alfonso.rodriguezm@....es>
Subject: Re: [PATCH v2] fpga: zynq-fpga: Ensure proper xCAP interface switch

On 2023-05-31 at 15:26:24 +0530, Nava kishore Manne wrote:
> From: Alfonso Rodriguez <alfonso.rodriguezm@....es>
> 
> The Zynq platform has PCAP, ICAP and JTAG interfaces for configuring
> programmable logic (PL). The existing driver implementation uses the
> PCAP interface to configure the PL. Before switching the PL configuration
> interface from PCAP to ICAP make sure that all outstanding Transactions
> relevant to the PL configuration should be completed by the PCAP interface
> otherwise it may lead to PL configuration issues.
> 
> This patch provides a required fix to ensure that all existing PL
> transactions are completed before switching from PCAP to ICAP.
> 
> For detailed information relevant to PL configuration interfaces refer
> Zynq 7000 TRM (section 6.5.1).
> Link: https://docs.xilinx.com/v/u/en-US/ug585-Zynq-7000-TRM
> 
> Signed-off-by: Alfonso Rodriguez <alfonso.rodriguezm@....es>
> Signed-off-by: Nava kishore Manne <nava.kishore.manne@....com>
> ---
> Changes for v2:
>               - Updated commit message and added Doc link as suggested by Yilun.
> 
>  drivers/fpga/zynq-fpga.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/fpga/zynq-fpga.c b/drivers/fpga/zynq-fpga.c
> index ae0da361e6c6..88db9ac36887 100644
> --- a/drivers/fpga/zynq-fpga.c
> +++ b/drivers/fpga/zynq-fpga.c
> @@ -493,15 +493,16 @@ static int zynq_fpga_ops_write_complete(struct fpga_manager *mgr,
>  	if (err)
>  		return err;
>  
> -	/* Release 'PR' control back to the ICAP */
> -	zynq_fpga_write(priv, CTRL_OFFSET,
> -		zynq_fpga_read(priv, CTRL_OFFSET) & ~CTRL_PCAP_PR_MASK);
> -
>  	err = zynq_fpga_poll_timeout(priv, INT_STS_OFFSET, intr_status,
>  				     intr_status & IXR_PCFG_DONE_MASK,
>  				     INIT_POLL_DELAY,
>  				     INIT_POLL_TIMEOUT);
>  
> +	/* Release 'PR' control back to the ICAP */
> +	zynq_fpga_write(priv, CTRL_OFFSET,
> +			zynq_fpga_read(priv, CTRL_OFFSET)
> +			& ~CTRL_PCAP_PR_MASK);

Don't put the & at the beginning of the line:

	zynq_fpga_read(priv, CTRL_OFFSET) &
	~CTRL_PCAP_PR_MASK);

or just:
	zynq_fpga_read(priv, CTRL_OFFSET) & ~CTRL_PCAP_PR_MASK);

80 lines is not a must now.

Others look good to me.

Thanks,
Yilun

> +
>  	clk_disable(priv->clk);
>  
>  	if (err)
> -- 
> 2.25.1
>