[PATCH 1/2] DMA: fix AMBA PL08x driver issue with 64bit DMA address type
Andre Przywara
andre.przywara at linaro.org
Thu Aug 15 17:07:26 EDT 2013
On 08/14/2013 09:13 PM, Rob Herring wrote:
> On Wed, Aug 14, 2013 at 8:00 AM, Russell King - ARM Linux
> <linux at arm.linux.org.uk> wrote:
>> NAK.
>
> This patch has nothing to do with dma masks or your dma mask series.
> The code deals with bus alignment and cleans up the code to do
> alignment operations in a sane way compared to modulo operator. The
> only thing 64-bit dma_addr_t did was expose crap code.
I agree. Actually I'd see the DMA mask thing just as an opportunity to
fix this code, not as the reason. I guess there are gazillions of
drivers in the ARM world which have problems with any address related
variable being bigger than 32bit, and those should all be fixed eventually.
> Perhaps bus_addr_offset needs a better name to indicate it is dealing
> with bus alignment rather than bus address offset.
Actually my first patch version called this function
unaligned_bus_addr(), but this was rather odd with the one non-boolean
usage of it - where it actually wants to know the offset.
Regards,
Andre.
>> On Wed, Aug 14, 2013 at 02:52:08PM +0200, Andre Przywara wrote:
>>> In Rob's recent pull request the patch
>>> ARM: highbank: select ARCH_DMA_ADDR_T_64BIT for LPAE
>>> promotes dma_addr_t to 64bit, which breaks compilation of the
>>> AMBA PL08x DMA driver.
>>> GCC has no function for the 64bit/8bit modulo operation.
>>> Looking more closely the divisor can only be 1, 2 or 4, so the full
>>> featured '%' modulo operation is overkill and can be replaced by
>>> simple bit masking.
>>>
>>> Signed-off-by: Andre Przywara <andre.przywara at linaro.org>
>>> ---
>>> drivers/dma/amba-pl08x.c | 16 ++++++++++------
>>> 1 file changed, 10 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
>>> index 06fe45c..29e1cf9 100644
>>> --- a/drivers/dma/amba-pl08x.c
>>> +++ b/drivers/dma/amba-pl08x.c
>>> @@ -286,6 +286,11 @@ static inline struct pl08x_txd *to_pl08x_txd(struct dma_async_tx_descriptor *tx)
>>> return container_of(tx, struct pl08x_txd, vd.tx);
>>> }
>>>
>>> +static int bus_addr_offset(struct pl08x_bus_data *bus)
>>> +{
>>> + return bus->addr & (bus->buswidth - 1);
>>> +}
>>> +
>>> /*
>>> * Mux handling.
>>> *
>>> @@ -886,8 +891,8 @@ static int pl08x_fill_llis_for_desc(struct pl08x_driver_data *pl08x,
>>> return 0;
>>> }
>>>
>>> - if ((bd.srcbus.addr % bd.srcbus.buswidth) ||
>>> - (bd.dstbus.addr % bd.dstbus.buswidth)) {
>>> + if (bus_addr_offset(&bd.srcbus) ||
>>> + bus_addr_offset(&bd.dstbus)) {
>>> dev_err(&pl08x->adev->dev,
>>> "%s src & dst address must be aligned to src"
>>> " & dst width if peripheral is flow controller",
>>> @@ -908,9 +913,8 @@ static int pl08x_fill_llis_for_desc(struct pl08x_driver_data *pl08x,
>>> */
>>> if (bd.remainder < mbus->buswidth)
>>> early_bytes = bd.remainder;
>>> - else if ((mbus->addr) % (mbus->buswidth)) {
>>> - early_bytes = mbus->buswidth - (mbus->addr) %
>>> - (mbus->buswidth);
>>> + else if (bus_addr_offset(mbus)) {
>>> + early_bytes = mbus->buswidth - bus_addr_offset(mbus);
>>> if ((bd.remainder - early_bytes) < mbus->buswidth)
>>> early_bytes = bd.remainder;
>>> }
>>> @@ -928,7 +932,7 @@ static int pl08x_fill_llis_for_desc(struct pl08x_driver_data *pl08x,
>>> * Master now aligned
>>> * - if slave is not then we must set its width down
>>> */
>>> - if (sbus->addr % sbus->buswidth) {
>>> + if (bus_addr_offset(sbus)) {
>>> dev_dbg(&pl08x->adev->dev,
>>> "%s set down bus width to one byte\n",
>>> __func__);
>>> --
>>> 1.7.12.1
>>>
>>
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