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

From: Boris Brezillon <[email-masked]>
Date: Thu, 21 May 2020 22:16:58 +0200

On Fri, 22 May 2020 01:33:15 +0530
Pratyush Yadav <[email-masked]> wrote:

> On 22/05/20 01:11AM, Pratyush Yadav wrote:
> > On 21/05/20 08:22PM, Boris Brezillon wrote:  
> > > On Wed, 20 May 2020 22:00:38 +0530
> > > Pratyush Yadav <[email-masked]> 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 <[email-masked]>
> > > > ---
> > > >  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.  
> 
> Scratch that. Big/little endian issue. If you'd drop your Signed-off-by, 
> I'll write the commit message and patch it in.

Just add a Suggested-by, that should be fine.

>   
> > > --->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;
> > >    
> 

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