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

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Date:   Sat, 23 May 2020 02:00:02 +0530
From:   Pratyush Yadav <me@...avpratyush.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     Pratyush Yadav <p.yadav@...com>,
        Richard Weinberger <richard@....at>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Mason Yang <masonccyang@...c.com.tw>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Sekhar Nori <nsekhar@...com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        linux-kernel@...r.kernel.org,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Mark Brown <broonie@...nel.org>, linux-mtd@...ts.infradead.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-mediatek@...ts.infradead.org, linux-spi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v7 02/20] spi: spi-mem: allow specifying a command's
 extension

On 22/05/20 05:32PM, Boris Brezillon wrote:
> 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.

How about the patch below before this patch? The supports_op() will 
reject multi-byte opcodes anyway, so we only care about single-byte 
opcodes for now. Multi-byte opcodes can be patched and tested later. 
This avoids squashing changes in this patch and having the changes split 
over two patches; one before and one after.

-- 8< --
diff --git a/drivers/spi/spi-mxic.c b/drivers/spi/spi-mxic.c
index 69491f3a515d..4e4292f0ee1d 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 opcode = op->cmd.opcode & 0xff;
 
 	ret = mxic_spi_set_freq(mxic, mem->spi->max_speed_hz);
 	if (ret)
@@ -393,7 +394,7 @@ 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);
+	ret = mxic_spi_data_xfer(mxic, &opcode, NULL, 1);
 	if (ret)
 		goto out;
 
-- 
Regards,
Pratyush Yadav