linux-kernel - Re: [PATCH v12 1/6] fpga: Add flag to indicate SPI bitstream is bit-reversed

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Message-ID: <CANk1AXT7aws86D2DbtoQseihxBdcQAYf22oLKA7D7K1uqRJdiw@mail.gmail.com>
Date:   Mon, 5 Jun 2017 10:11:00 -0500
From:   Alan Tull <atull@...nel.org>
To:     Joshua Clayton <stillcompiling@...il.com>
Cc:     Moritz Fischer <moritz.fischer@...us.com>,
        Anatolij Gustschin <agust@...x.de>,
        Bastian Stender <bst@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        Russell King <linux@...linux.org.uk>,
        linux-fpga@...r.kernel.org,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v12 1/6] fpga: Add flag to indicate SPI bitstream is bit-reversed

On Fri, Jun 2, 2017 at 3:30 PM, Joshua Clayton <stillcompiling@...il.com> wrote:
> From: Anatolij Gustschin <agust@...x.de>
>
> Add a flag that is passed to the write_init() callback,
> indicating that the SPI bitstream starts with LSB first.
> SPI controllers usually send data with MSB first. If an
> FPGA expects bitstream data as LSB first, the data must
> be reversed either by the SPI controller or by the driver.
>
> Alternatively the bitstream could be prepared as bit-reversed
> to avoid the bit-swapping while sending. This flag indicates
> such bit-reversed SPI bitstream. The low-level driver will
> deal with the flag and perform bit-reversing if needed.
>
> Signed-off-by: Anatolij Gustschin <agust@...x.de>
> Signed-off-by: Joshua Clayton <stillcompiling@...il.com>

Signed-off-by: Alan Tull <atull@...nel.org>

> ---
>
> Changes from v11 (all in patch 4/4)
> - Change "Altera V FPGA" to simply "Altera FPGA"
> - Change the devicetree name to a generic "fpga: fpga@0"
>   from "fpga_spi: cyclonespi@0"
>
>  include/linux/fpga/fpga-mgr.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
> index b4ac24c4411d..01c348ca38b7 100644
> --- a/include/linux/fpga/fpga-mgr.h
> +++ b/include/linux/fpga/fpga-mgr.h
> @@ -67,10 +67,12 @@ enum fpga_mgr_states {
>   * FPGA Manager flags
>   * FPGA_MGR_PARTIAL_RECONFIG: do partial reconfiguration if supported
>   * FPGA_MGR_EXTERNAL_CONFIG: FPGA has been configured prior to Linux booting
> + * FPGA_MGR_BITSTREAM_LSB_FIRST: SPI bitstream bit order is LSB first
>   */
>  #define FPGA_MGR_PARTIAL_RECONFIG      BIT(0)
>  #define FPGA_MGR_EXTERNAL_CONFIG       BIT(1)
>  #define FPGA_MGR_ENCRYPTED_BITSTREAM   BIT(2)
> +#define FPGA_MGR_BITSTREAM_LSB_FIRST   BIT(3)
>
>  /**
>   * struct fpga_image_info - information specific to a FPGA image
> --
> 2.11.0
>