linux-kernel - Re: [PATCH v7 02/20] spi: spi-mem: allow specifying a command's extension

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Date:   Fri, 22 May 2020 17:32:54 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Pratyush Yadav <p.yadav@...com>,
        Richard Weinberger <richard@....at>
Cc:     Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        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 v7 02/20] spi: spi-mem: allow specifying a command's
 extension

On Fri, 22 May 2020 15:42:43 +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.

A slightly different version of patch 5 should go before this patch,
otherwise your series is not bisectable. By slightly different, I mean
that you should only write one byte, but put this byte in a temporary
var. Or maybe you can squash patch 5 in this one and mention why you do
so in your commit message.

> 
> Signed-off-by: Pratyush Yadav <p.yadav@...com>
> ---
>  drivers/spi/spi-mem.c       | 5 ++++-
>  include/linux/spi/spi-mem.h | 6 +++++-
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index 93e255287ab9..29dcd1d62710 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -159,6 +159,9 @@ bool spi_mem_default_supports_op(struct spi_mem *mem,
>  	if (op->cmd.dtr || op->addr.dtr || op->dummy.dtr || op->data.dtr)
>  		return false;
>  
> +	if (op->cmd.nbytes != 1)
> +		return false;
> +
>  	return true;
>  }
>  EXPORT_SYMBOL_GPL(spi_mem_default_supports_op);
> @@ -173,7 +176,7 @@ static bool spi_mem_buswidth_is_valid(u8 buswidth)
>  
>  static int spi_mem_check_op(const struct spi_mem_op *op)
>  {
> -	if (!op->cmd.buswidth)
> +	if (!op->cmd.buswidth || !op->cmd.nbytes)
>  		return -EINVAL;
>  
>  	if ((op->addr.nbytes && !op->addr.buswidth) ||
> diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
> index e3dcb956bf61..159463cc659c 100644
> --- a/include/linux/spi/spi-mem.h
> +++ b/include/linux/spi/spi-mem.h
> @@ -17,6 +17,7 @@
>  	{							\
>  		.buswidth = __buswidth,				\
>  		.opcode = __opcode,				\
> +		.nbytes = 1,					\
>  	}
>  
>  #define SPI_MEM_OP_ADDR(__nbytes, __val, __buswidth)		\
> @@ -69,6 +70,8 @@ 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 +97,10 @@ enum spi_mem_data_dir {
>   */
>  struct spi_mem_op {
>  	struct {
> +		u8 nbytes;
>  		u8 buswidth;
>  		u8 dtr : 1;
> -		u8 opcode;
> +		u16 opcode;
>  	} cmd;
>  
>  	struct {