Re: [PATCH 2/3] spi: mxic: patch for octal DTR mode support

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Pratyush,

Pratyush Yadav <p.yadav@ti.com> wrote on Tue, 2 Feb 2021 01:40:30 +0530:

> On 01/02/21 03:49PM, Miquel Raynal wrote:
> > Hello,
> > 
> > zhengxunli <zhengxunli@mxic.com.tw> wrote on Fri, 29 Jan 2021 16:13:37
> > +0800:
> >   
> > > Driver patch for octal 8D-8D-8D mode support.
> > > 
> > > Signed-off-by: zhengxunli <zhengxunli@mxic.com.tw>
> > > ---
> > >  drivers/spi/spi-mxic.c | 33 ++++++++++++++++++++++-----------
> > >  1 file changed, 22 insertions(+), 11 deletions(-)
> > > 
> > > diff --git a/drivers/spi/spi-mxic.c b/drivers/spi/spi-mxic.c
> > > index 96b4182..821328a 100644
> > > --- a/drivers/spi/spi-mxic.c
> > > +++ b/drivers/spi/spi-mxic.c
> > > @@ -335,8 +335,8 @@ static int mxic_spi_data_xfer(struct mxic_spi *mxic, const void *txbuf,
> > >  static bool mxic_spi_mem_supports_op(struct spi_mem *mem,
> > >  				     const struct spi_mem_op *op)
> > >  {
> > > -	if (op->data.buswidth > 4 || op->addr.buswidth > 4 ||
> > > -	    op->dummy.buswidth > 4 || op->cmd.buswidth > 4)
> > > +	if (op->data.buswidth > 8 || op->addr.buswidth > 8 ||
> > > +	    op->dummy.buswidth > 8 || op->cmd.buswidth > 8)
> > >  		return false;  
> 
> Can the controller support mixed DTR modes? For example, can it support 
> 4S-4D-4D operations? If no, then please add a check for that here. See 
> cqspi_supports_mem_op() for an example.
> 
> > >  
> > >  	if (op->data.nbytes && op->dummy.nbytes &&
> > > @@ -346,7 +346,7 @@ static bool mxic_spi_mem_supports_op(struct spi_mem *mem,
> > >  	if (op->addr.nbytes > 7)
> > >  		return false;
> > >  
> > > -	return spi_mem_default_supports_op(mem, op);
> > > +	return true;  
> > 
> > Does not seem correct. Why would you drop this check?  
> 
> spi_mem_default_supports_op() rejects DTR ops for backward 
> compatibility.
> 
> But skipping that would mean skipping the spi_check_buswidth_req() calls 
> [0]. Maybe we should export that part as a library function so 
> controllers can use it and not have to roll their own logic?
> 
> [0] They are not _technically_ needed. Not calling them would mean the 
> spi-{rx,tx}-bus-width DT properties would be ignored. The negotiation 
> for supported opcodes will happen on what the controller _actually_ 
> supports and what SPI NOR says the flash supports. So for example you 
> can't force a octal capable flash to use quad mode. Not sure if that is 
> a good thing or a bad thing.

I don't think is a good idea to ignore the user inputs. If these
properties are populated one will not understand why, in this
particular case, they won't get parsed.

Perhaps having a spi_mem_dtr_supports_op() or something alike which
calls a common helper (eg. spi_mem_generic_supports_op()) shared
with spi_mem_default_supports_op() would make sense.

>  
> > >  }
> > >  
> > >  static int mxic_spi_mem_exec_op(struct spi_mem *mem,
> > > @@ -355,14 +355,15 @@ static int mxic_spi_mem_exec_op(struct spi_mem *mem,
> > >  	struct mxic_spi *mxic = spi_master_get_devdata(mem->spi->master);
> > >  	int nio = 1, i, ret;
> > >  	u32 ss_ctrl;
> > > -	u8 addr[8];
> > > -	u8 opcode = op->cmd.opcode;
> > > +	u8 addr[8], cmd[2];
> > >  
> > >  	ret = mxic_spi_set_freq(mxic, mem->spi->max_speed_hz);
> > >  	if (ret)
> > >  		return ret;
> > >  
> > > -	if (mem->spi->mode & (SPI_TX_QUAD | SPI_RX_QUAD))
> > > +	if (mem->spi->mode & (SPI_TX_OCTAL | SPI_RX_OCTAL))
> > > +		nio = 8;
> > > +	else if (mem->spi->mode & (SPI_TX_QUAD | SPI_RX_QUAD))  
> 
> Hmm, shouldn't you be looking at op->*.buswidth?
> 
> > >  		nio = 4;
> > >  	else if (mem->spi->mode & (SPI_TX_DUAL | SPI_RX_DUAL))
> > >  		nio = 2;
> > > @@ -374,19 +375,25 @@ static int mxic_spi_mem_exec_op(struct spi_mem *mem,
> > >  	       mxic->regs + HC_CFG);
> > >  	writel(HC_EN_BIT, mxic->regs + HC_EN);
> > >  
> > > -	ss_ctrl = OP_CMD_BYTES(1) | OP_CMD_BUSW(fls(op->cmd.buswidth) - 1);
> > > +	ss_ctrl = OP_CMD_BYTES(op->cmd.nbytes) |
> > > +		  OP_CMD_BUSW(fls(op->cmd.buswidth) - 1) |
> > > +		  (op->cmd.dtr ? OP_CMD_DDR : 0);
> > >  
> > >  	if (op->addr.nbytes)
> > >  		ss_ctrl |= OP_ADDR_BYTES(op->addr.nbytes) |
> > > -			   OP_ADDR_BUSW(fls(op->addr.buswidth) - 1);
> > > +			   OP_ADDR_BUSW(fls(op->addr.buswidth) - 1) |
> > > +			   (op->addr.dtr ? OP_ADDR_DDR : 0);
> > >  
> > >  	if (op->dummy.nbytes)
> > >  		ss_ctrl |= OP_DUMMY_CYC(op->dummy.nbytes);
> > >  
> > >  	if (op->data.nbytes) {
> > > -		ss_ctrl |= OP_DATA_BUSW(fls(op->data.buswidth) - 1);
> > > +		ss_ctrl |= OP_DATA_BUSW(fls(op->data.buswidth) - 1) |
> > > +			   (op->data.dtr ? OP_DATA_DDR : 0);
> > >  		if (op->data.dir == SPI_MEM_DATA_IN)
> > >  			ss_ctrl |= OP_READ;
> > > +			if (op->data.dtr)
> > > +				ss_ctrl |= OP_DQS_EN;
> > >  	}
> > >  
> > >  	writel(ss_ctrl, mxic->regs + SS_CTRL(mem->spi->chip_select));
> > > @@ -394,7 +401,10 @@ 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, &opcode, NULL, 1);
> > > +	for (i = 0; i < op->cmd.nbytes; i++)  
> > 
> > Can we add a check in mxic_spi_mem_check_op to ensure nbytes is never >
> > 2 ?
> >   
> > > +		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;
> > >  
> > > @@ -567,7 +577,8 @@ static int mxic_spi_probe(struct platform_device *pdev)
> > >  	master->bits_per_word_mask = SPI_BPW_MASK(8);
> > >  	master->mode_bits = SPI_CPOL | SPI_CPHA |
> > >  			SPI_RX_DUAL | SPI_TX_DUAL |
> > > -			SPI_RX_QUAD | SPI_TX_QUAD;
> > > +			SPI_RX_QUAD | SPI_TX_QUAD |
> > > +			SPI_RX_OCTAL | SPI_TX_OCTAL;
> > >  
> > >  	mxic_spi_hw_init(mxic);
> > >    
> > 
> > Otherwise looks fine.
> > 
> > Thanks,
> > Miquèl
> >   
> 

Thanks,
Miquèl

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