[PATCH 1/2] DMA: fix AMBA PL08x driver issue with 64bit DMA address type

[Rob Herring]

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.

Perhaps bus_addr_offset needs a better name to indicate it is dealing
with bus alignment rather than bus address offset.

Rob

> 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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