linux-kernel - Re: [PATCH v6 04/19] spi: spi-mem: allow specifying a command's extension

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Date:   Thu, 21 May 2020 20:22:56 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Pratyush Yadav <p.yadav@...com>
Cc:     Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mark Brown <broonie@...nel.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-spi@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, Sekhar Nori <nsekhar@...com>,
        Mason Yang <masonccyang@...c.com.tw>
Subject: Re: [PATCH v6 04/19] spi: spi-mem: allow specifying a command's
 extension

On Wed, 20 May 2020 22:00:38 +0530
Pratyush Yadav <p.yadav@...com> wrote:

> In xSPI mode, flashes expect 2-byte opcodes. The second byte is called
> the "command extension". There can be 3 types of extensions in xSPI:
> repeat, invert, and hex. When the extension type is "repeat", the same
> opcode is sent twice. When it is "invert", the second byte is the
> inverse of the opcode. When it is "hex" an additional opcode byte based
> is sent with the command whose value can be anything.
> 
> So, make opcode a 16-bit value and add a 'nbytes', similar to how
> multiple address widths are handled.
> 
> Signed-off-by: Pratyush Yadav <p.yadav@...com>
> ---
>  include/linux/spi/spi-mem.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
> index e3dcb956bf61..731bb64c6ba6 100644
> --- a/include/linux/spi/spi-mem.h
> +++ b/include/linux/spi/spi-mem.h
> @@ -69,6 +69,8 @@ enum spi_mem_data_dir {
>  
>  /**
>   * struct spi_mem_op - describes a SPI memory operation
> + * @cmd.nbytes: number of opcode bytes (only 1 or 2 are valid). The opcode is
> + *		sent MSB-first.
>   * @cmd.buswidth: number of IO lines used to transmit the command
>   * @cmd.opcode: operation opcode
>   * @cmd.dtr: whether the command opcode should be sent in DTR mode or not
> @@ -94,9 +96,10 @@ enum spi_mem_data_dir {
>   */
>  struct spi_mem_op {
>  	struct {
> +		u8 nbytes;
>  		u8 buswidth;
>  		u8 dtr : 1;
> -		u8 opcode;
> +		u16 opcode;
>  	} cmd;
>  
>  	struct {

As mentioned in one of my previous review, you should patch the mxic
driver before extending the opcode field:

--->8---
diff --git a/drivers/spi/spi-mxic.c b/drivers/spi/spi-mxic.c
index 69491f3a515d..c3f4136a7c1d 100644
--- a/drivers/spi/spi-mxic.c
+++ b/drivers/spi/spi-mxic.c
@@ -356,6 +356,7 @@ static int mxic_spi_mem_exec_op(struct spi_mem *mem,
        int nio = 1, i, ret;
        u32 ss_ctrl;
        u8 addr[8];
+       u8 cmd[2];
 
        ret = mxic_spi_set_freq(mxic, mem->spi->max_speed_hz);
        if (ret)
@@ -393,7 +394,10 @@ static int mxic_spi_mem_exec_op(struct spi_mem *mem,
        writel(readl(mxic->regs + HC_CFG) | HC_CFG_MAN_CS_ASSERT,
               mxic->regs + HC_CFG);
 
-       ret = mxic_spi_data_xfer(mxic, &op->cmd.opcode, NULL, 1);
+       for (i = 0; i < op->cmd.nbytes; i++)
+               cmd[i] = op->cmd.opcode >> (8 * (op->cmd.nbytes - i - 1));
+
+       ret = mxic_spi_data_xfer(mxic, cmd, NULL, op->cmd.nbytes);
        if (ret)
                goto out;