[RFC] mtd: atmel-quadspi: fix build issues

Submitted by Arnd Bergmann on July 21, 2017, 10:21 p.m.

Details

Message ID 20170721222204.3402340-1-arnd@arndb.de
State Under Review
Delegated to: Cyrille Pitchen
Headers show

Commit Message

Arnd Bergmann July 21, 2017, 10:21 p.m.
I ran into a link-time error with the atmel-quadspi driver on the
EBSA110 platform:

drivers/mtd/built-in.o: In function `atmel_qspi_run_command':
:(.text+0x1ee3c): undefined reference to `_memcpy_toio'
:(.text+0x1ee48): undefined reference to `_memcpy_fromio'

The problem is that _memcpy_toio/_memcpy_fromio are not available
on that platform, and we have to prevent building the driver there.

A related problem is that the functions are not portable APIs
and should not be called directly from a device driver. On
little-endian machines, the regular memcpy_toio/memcpy_fromio
functions are defined as optimized versions using multi-byte
transfers that are much faster.

Cyrille mentioned that initially using memcpy_toio/memcpy_fromio
did not work, but I suspect that this was the result of a bug
that has since been fixed. With that change, we can also
compile-test on other architectures.

Link: http://lists.infradead.org/pipermail/linux-mtd/2016-July/068583.html
Fixes: 161aaab8a067 ("mtd: atmel-quadspi: add driver for Atmel QSPI controller")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/mtd/spi-nor/Kconfig         | 2 +-
 drivers/mtd/spi-nor/atmel-quadspi.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

Comments

Cyrille Pitchen Aug. 1, 2017, 7:41 p.m.
Hi Arnd,

Le 22/07/2017 à 00:21, Arnd Bergmann a écrit :
> I ran into a link-time error with the atmel-quadspi driver on the
> EBSA110 platform:
> 
> drivers/mtd/built-in.o: In function `atmel_qspi_run_command':
> :(.text+0x1ee3c): undefined reference to `_memcpy_toio'
> :(.text+0x1ee48): undefined reference to `_memcpy_fromio'
> 
> The problem is that _memcpy_toio/_memcpy_fromio are not available
> on that platform, and we have to prevent building the driver there.
> 
> A related problem is that the functions are not portable APIs
> and should not be called directly from a device driver. On
> little-endian machines, the regular memcpy_toio/memcpy_fromio
> functions are defined as optimized versions using multi-byte
> transfers that are much faster.
> 
> Cyrille mentioned that initially using memcpy_toio/memcpy_fromio
> did not work, but I suspect that this was the result of a bug
> that has since been fixed. With that change, we can also
> compile-test on other architectures.
> 
> Link: http://lists.infradead.org/pipermail/linux-mtd/2016-July/068583.html
> Fixes: 161aaab8a067 ("mtd: atmel-quadspi: add driver for Atmel QSPI controller")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/mtd/spi-nor/Kconfig         | 2 +-
>  drivers/mtd/spi-nor/atmel-quadspi.c | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/Kconfig b/drivers/mtd/spi-nor/Kconfig
> index 293c8a4d1e49..22e5fc4080f8 100644
> --- a/drivers/mtd/spi-nor/Kconfig
> +++ b/drivers/mtd/spi-nor/Kconfig
> @@ -41,7 +41,7 @@ config SPI_ASPEED_SMC
>  
>  config SPI_ATMEL_QUADSPI
>  	tristate "Atmel Quad SPI Controller"
> -	depends on ARCH_AT91 || (ARM && COMPILE_TEST)
> +	depends on ARCH_AT91 || (COMPILE_TEST && !ARCH_EBSA110)
>  	depends on OF && HAS_IOMEM
>  	help
>  	  This enables support for the Quad SPI controller in master mode.
> diff --git a/drivers/mtd/spi-nor/atmel-quadspi.c b/drivers/mtd/spi-nor/atmel-quadspi.c
> index ba76fa8f2031..ff3849106e77 100644
> --- a/drivers/mtd/spi-nor/atmel-quadspi.c
> +++ b/drivers/mtd/spi-nor/atmel-quadspi.c
> @@ -208,9 +208,9 @@ static int atmel_qspi_run_transfer(struct atmel_qspi *aq,
>  	if (cmd->enable.bits.address)
>  		ahb_mem += cmd->address;
>  	if (cmd->tx_buf)
> -		_memcpy_toio(ahb_mem, cmd->tx_buf, cmd->buf_len);
> +		memcpy_toio(ahb_mem, cmd->tx_buf, cmd->buf_len);
>  	else
> -		_memcpy_fromio(cmd->rx_buf, ahb_mem, cmd->buf_len);
> +		memcpy_fromio(cmd->rx_buf, ahb_mem, cmd->buf_len);
>

At least on AT91 platforms and likely on most ARM boards,
memcpy_fromio == memcpy_toio == memcpy.

I got some sama5d2 hardware last week, so I'll try to test your patch
within few days because as you said maybe memcpy() was broken when I
developed this driver at first but now memcpy() is likely to have been
fixed so it might be interesting to get rid of _memcpy_fromio() and
_memcpy_toio() because this is not the first time those 2 functions have
created issues when building the Atmel Quad SPI driver on other platforms.

So thanks for you're patch, I'll give it a try :)

Best regards,

Cyrille


>  	return 0;
>  }
>
Arnd Bergmann Aug. 1, 2017, 8:10 p.m.
On Tue, Aug 1, 2017 at 9:41 PM, Cyrille Pitchen
<cyrille.pitchen@wedev4u.fr> wrote:
> Le 22/07/2017 à 00:21, Arnd Bergmann a écrit :

>> --- a/drivers/mtd/spi-nor/atmel-quadspi.c
>> +++ b/drivers/mtd/spi-nor/atmel-quadspi.c
>> @@ -208,9 +208,9 @@ static int atmel_qspi_run_transfer(struct atmel_qspi *aq,
>>       if (cmd->enable.bits.address)
>>               ahb_mem += cmd->address;
>>       if (cmd->tx_buf)
>> -             _memcpy_toio(ahb_mem, cmd->tx_buf, cmd->buf_len);
>> +             memcpy_toio(ahb_mem, cmd->tx_buf, cmd->buf_len);
>>       else
>> -             _memcpy_fromio(cmd->rx_buf, ahb_mem, cmd->buf_len);
>> +             memcpy_fromio(cmd->rx_buf, ahb_mem, cmd->buf_len);
>>
>
> At least on AT91 platforms and likely on most ARM boards,
> memcpy_fromio == memcpy_toio == memcpy.

Just to give more background, it's a bit more complicated than this:

On big-endian kernels, memcpy_fromio/memcpy_toio are
always defined as _memcpy_fromio/_memcpy_toio so we
do byte load/store operations in the correct order, while
little-endian kernels have the optimized mmiocpy() that redirects
to memcpy(). This is true for all ARM platforms other than EBSA110
IIRC.

Also, mmiocpy is an exported symbol that aliases to the external
memcpy definition, but we can't call memcpy directly, because gcc
knows how to inline calls to memcpy() and replace them by direct
load/store instructions that might be unaligned and trap on uncached
mmio areas.

> I got some sama5d2 hardware last week, so I'll try to test your patch
> within few days because as you said maybe memcpy() was broken when I
> developed this driver at first but now memcpy() is likely to have been
> fixed so it might be interesting to get rid of _memcpy_fromio() and
> _memcpy_toio() because this is not the first time those 2 functions have
> created issues when building the Atmel Quad SPI driver on other platforms.
>
> So thanks for you're patch, I'll give it a try :)

Ok, thanks.

       Arnd

Patch hide | download patch | download mbox

diff --git a/drivers/mtd/spi-nor/Kconfig b/drivers/mtd/spi-nor/Kconfig
index 293c8a4d1e49..22e5fc4080f8 100644
--- a/drivers/mtd/spi-nor/Kconfig
+++ b/drivers/mtd/spi-nor/Kconfig
@@ -41,7 +41,7 @@  config SPI_ASPEED_SMC
 
 config SPI_ATMEL_QUADSPI
 	tristate "Atmel Quad SPI Controller"
-	depends on ARCH_AT91 || (ARM && COMPILE_TEST)
+	depends on ARCH_AT91 || (COMPILE_TEST && !ARCH_EBSA110)
 	depends on OF && HAS_IOMEM
 	help
 	  This enables support for the Quad SPI controller in master mode.
diff --git a/drivers/mtd/spi-nor/atmel-quadspi.c b/drivers/mtd/spi-nor/atmel-quadspi.c
index ba76fa8f2031..ff3849106e77 100644
--- a/drivers/mtd/spi-nor/atmel-quadspi.c
+++ b/drivers/mtd/spi-nor/atmel-quadspi.c
@@ -208,9 +208,9 @@  static int atmel_qspi_run_transfer(struct atmel_qspi *aq,
 	if (cmd->enable.bits.address)
 		ahb_mem += cmd->address;
 	if (cmd->tx_buf)
-		_memcpy_toio(ahb_mem, cmd->tx_buf, cmd->buf_len);
+		memcpy_toio(ahb_mem, cmd->tx_buf, cmd->buf_len);
 	else
-		_memcpy_fromio(cmd->rx_buf, ahb_mem, cmd->buf_len);
+		memcpy_fromio(cmd->rx_buf, ahb_mem, cmd->buf_len);
 
 	return 0;
 }