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

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Date:   Fri, 22 May 2020 01:11:31 +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>,
        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 21/05/20 08:22PM, Boris Brezillon wrote:
> 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:

IIUC, this patchset doesn't break original functionality of the driver. 
It will work like before with 1-byte opcodes. So I don't think it is the 
responsibility of this patchset to enhance the driver. It didn't work 
before with 2-byte opcodes, it won't work now. IMO this should be a 
separate, independent change.
 
> --->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;
>  

-- 
Regards,
Pratyush Yadav
Texas Instruments India