2018-12-07 13:10:50

by Christophe Leroy

Subject: [PATCH] gpio: max7301: fix driver for use with CONFIG_VMAP_STACK

spi_read() and spi_write() require DMA-safe memory. When
CONFIG_VMAP_STACK is selected, those functions cannot be used
with buffers on stack.

This patch replaces calls to spi_read() and spi_write() by
spi_write_then_read() which doesn't require DMA-safe buffers.

Fixes: 0c36ec314735 ("gpio: gpio driver for max7301 SPI GPIO expander")
Cc: <[email protected]>
Signed-off-by: Christophe Leroy <[email protected]>
---
drivers/gpio/gpio-max7301.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/gpio/gpio-max7301.c b/drivers/gpio/gpio-max7301.c
index 68c7942d0a3c..6f7d12ba2f74 100644
--- a/drivers/gpio/gpio-max7301.c
+++ b/drivers/gpio/gpio-max7301.c
@@ -25,7 +25,7 @@ static int max7301_spi_write(struct device *dev, unsigned int reg,
struct spi_device *spi = to_spi_device(dev);
u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);

- return spi_write(spi, (const u8 *)&word, sizeof(word));
+ return spi_write_then_read(spi, &word, sizeof(word), NULL, 0);
}

/* A read from the MAX7301 means two transfers; here, one message each */
@@ -37,14 +37,8 @@ static int max7301_spi_read(struct device *dev, unsigned int reg)
struct spi_device *spi = to_spi_device(dev);

word = 0x8000 | (reg << 8);
- ret = spi_write(spi, (const u8 *)&word, sizeof(word));
- if (ret)
- return ret;
- /*
- * This relies on the fact, that a transfer with NULL tx_buf shifts out
- * zero bytes (=NOOP for MAX7301)
- */
- ret = spi_read(spi, (u8 *)&word, sizeof(word));
+ ret = spi_write_then_read(spi, &word, sizeof(word), &word,
+ sizeof(word));
if (ret)
return ret;
return word & 0xff;
--
2.13.3

2018-12-16 00:16:32

by Linus Walleij

Subject: Re: [PATCH] gpio: max7301: fix driver for use with CONFIG_VMAP_STACK

On Fri, Dec 7, 2018 at 2:07 PM Christophe Leroy <[email protected]> wrote:

> spi_read() and spi_write() require DMA-safe memory. When
> CONFIG_VMAP_STACK is selected, those functions cannot be used
> with buffers on stack.
>
> This patch replaces calls to spi_read() and spi_write() by
> spi_write_then_read() which doesn't require DMA-safe buffers.
>
> Fixes: 0c36ec314735 ("gpio: gpio driver for max7301 SPI GPIO expander")
> Cc: <[email protected]>
> Signed-off-by: Christophe Leroy <[email protected]>

Patch applied for fixes.

Yours,
Linus Walleij