lkml.org 
[lkml]   [2016]   [Sep]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] serial: stm32: use mapbase instead of membase for DMA
From
Date
Hi Arnd

On 09/23/2016 09:38 PM, Arnd Bergmann wrote:
> Building this driver with a 64-bit dma_addr_t type results in
> a compiler warning:
>
> drivers/tty/serial/stm32-usart.c: In function 'stm32_of_dma_rx_probe':
> drivers/tty/serial/stm32-usart.c:746:20: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
> drivers/tty/serial/stm32-usart.c: In function 'stm32_of_dma_tx_probe':
> drivers/tty/serial/stm32-usart.c:818:20: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>
> While the type conversion here is harmless, this hints at a different
> problem: we pass an __iomem pointer into a DMA engine, which expects
> a phys_addr_t. This happens to work because stm32 has no MMU and
> ioremap() is an identity mapping here, but it's still an incorrect
> API use. Using dma_addr_t is doubly wrong here, because that would
> be the result of dma_map_single() rather than the physical address.
>
> Using the mapbase instead fixes multiple issues:
>
> - the warning is gone
> - we don't go through ioremap in error
> - the cast is gone, making it use the correct resource_size_t/phys_addr_t
> type in the process.
>
> Fixes: 3489187204eb ("serial: stm32: adding dma support")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/tty/serial/stm32-usart.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
> index 4d3001b77e7e..2adb678a863b 100644
> --- a/drivers/tty/serial/stm32-usart.c
> +++ b/drivers/tty/serial/stm32-usart.c
> @@ -743,7 +743,7 @@ static int stm32_of_dma_rx_probe(struct stm32_port *stm32port,
>
> /* Configure DMA channel */
> memset(&config, 0, sizeof(config));
> - config.src_addr = (dma_addr_t)port->membase + ofs->rdr;
> + config.src_addr = port->mapbase + ofs->rdr;
> config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
>
> ret = dmaengine_slave_config(stm32port->rx_ch, &config);
> @@ -815,7 +815,7 @@ static int stm32_of_dma_tx_probe(struct stm32_port *stm32port,
>
> /* Configure DMA channel */
> memset(&config, 0, sizeof(config));
> - config.dst_addr = (dma_addr_t)port->membase + ofs->tdr;
> + config.dst_addr = port->mapbase + ofs->tdr;
> config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
>
> ret = dmaengine_slave_config(stm32port->tx_ch, &config);
>

Indeed, thanks for this finding.

Reviewed-by: Gerald Baeza <gerald.baeza@st.com>

\
 
 \ /
  Last update: 2016-09-26 15:23    [W:0.110 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site