linux-kernel - Re: [PATCH v2 04/11] spi: spi-mem: allow specifying a command's extension

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Message-ID: <20200228094142.436fjee5fb7w6pd2@ti.com>
Date:   Fri, 28 Feb 2020 15:11:42 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     Boris Brezillon <boris.brezillon@...labora.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>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        <devicetree@...r.kernel.org>, Sekhar Nori <nsekhar@...com>,
        <linux-kernel@...r.kernel.org>, <linux-spi@...r.kernel.org>,
        <linux-mtd@...ts.infradead.org>
Subject: Re: [PATCH v2 04/11] spi: spi-mem: allow specifying a command's
 extension

On 27/02/20 05:44PM, Boris Brezillon wrote:
> On Wed, 26 Feb 2020 15:06:56 +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.
> > 
> > Signed-off-by: Pratyush Yadav <p.yadav@...com>
> > ---
> >  drivers/spi/spi-mem.c       | 23 +++++++++++++++++++++++
> >  include/linux/spi/spi-mem.h | 24 ++++++++++++++++++++++++
> >  2 files changed, 47 insertions(+)
> > 
> > diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> > index cb13e0878b95..3838ddc9aeec 100644
> > --- a/drivers/spi/spi-mem.c
> > +++ b/drivers/spi/spi-mem.c
> > @@ -462,6 +462,29 @@ int spi_mem_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
> >  }
> >  EXPORT_SYMBOL_GPL(spi_mem_adjust_op_size);
> >  
> > +int spi_mem_get_cmd_ext(const struct spi_mem_op *op, u8 *ext)
> > +{
> > +	switch (op->cmd.ext_type) {
> > +	case SPI_MEM_EXT_INVERT:
> > +		*ext = ~op->cmd.opcode;
> > +		break;
> > +
> > +	case SPI_MEM_EXT_REPEAT:
> > +		*ext = op->cmd.opcode;
> > +		break;
> > +
> > +	case SPI_MEM_EXT_HEX:
> > +		*ext = op->cmd.ext;
> > +		break;
> > +
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(spi_mem_get_cmd_ext);
> > +
> >  static ssize_t spi_mem_no_dirmap_read(struct spi_mem_dirmap_desc *desc,
> >  				      u64 offs, size_t len, void *buf)
> >  {
> > diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
> > index 4669082b4e3b..06ccab17e4d0 100644
> > --- a/include/linux/spi/spi-mem.h
> > +++ b/include/linux/spi/spi-mem.h
> > @@ -67,11 +67,31 @@ enum spi_mem_data_dir {
> >  	SPI_MEM_DATA_OUT,
> >  };
> >  
> > +/**
> > + * enum spi_mem_cmd_ext - describes the command opcode extension in DTR mode
> > + * @SPI_MEM_EXT_NONE: no extension. This is the default, and is used in Legacy
> > + *		      SPI mode
> > + * @SPI_MEM_EXT_REPEAT: the extension is same as the opcode
> > + * @SPI_MEM_EXT_INVERT: the extension is the bitwise inverse of the opcode
> > + * @SPI_MEM_EXT_HEX: the extension is any hex value. The command and opcode
> > + *		     combine to form a 16-bit opcode.
> > + */
> > +enum spi_mem_cmd_ext {
> > +	SPI_MEM_EXT_NONE = 0,
> > +	SPI_MEM_EXT_REPEAT,
> > +	SPI_MEM_EXT_INVERT,
> > +	SPI_MEM_EXT_HEX,
> > +};
> > +
> >  /**
> >   * struct spi_mem_op - describes a SPI memory operation
> >   * @cmd.buswidth: number of IO lines used to transmit the command
> >   * @cmd.opcode: operation opcode
> >   * @cmd.is_dtr: whether the command opcode should be sent in DTR mode or not
> > + * @cmd.ext_type: type of the command opcode extension in DTR mode
> > + * @cmd.ext: value of the command opcode extension in DTR mode. It is
> > + *	     only set when 'ext_type' is 'SPI_MEM_EXT_HEX'. In all other
> > + *	     cases, the extension can be directly derived from the opcode.
> >   * @addr.nbytes: number of address bytes to send. Can be zero if the operation
> >   *		 does not need to send an address
> >   * @addr.buswidth: number of IO lines used to transmit the address cycles
> > @@ -97,6 +117,8 @@ struct spi_mem_op {
> >  		u8 buswidth;
> >  		u8 opcode;
> >  		bool is_dtr;
> > +		enum spi_mem_cmd_ext ext_type;
> > +		u8 ext;
> 
> Could we instead make opcode an u16 (or u8[2]) and pass the number of
> bytes, as done for the other addr? Mode can be extracted from the
> opcode/nbytes values if really needed, and the caller would be
> responsible for filling those fields properly (which shouldn't be too
> hard)

Ok. Will do.
 
> >  	} cmd;
> >  
> >  	struct {
> > @@ -361,6 +383,8 @@ int spi_mem_driver_register_with_owner(struct spi_mem_driver *drv,
> >  
> >  void spi_mem_driver_unregister(struct spi_mem_driver *drv);
> >  
> > +int spi_mem_get_cmd_ext(const struct spi_mem_op *op, u8 *ext);
> > +
> >  #define spi_mem_driver_register(__drv)                                  \
> >  	spi_mem_driver_register_with_owner(__drv, THIS_MODULE)
> >  
> 

-- 
Regards,
Pratyush Yadav
Texas Instruments India