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authorAndy Shevchenko <andriy.shevchenko@linux.intel.com>2015-09-14 11:55:36 +0300
committerVinod Koul <vinod.koul@intel.com>2015-09-25 07:51:16 +0530
commit0b23a1ece9be2c3e04c3b8d3594a1ada1fa1ae50 (patch)
treeb72250d28adee020ab9ca2ec7c135466ddbf15a4 /drivers/dma/idma64.c
parentc1492b4c541e3a382b60f1b5879cd3c4d246ad31 (diff)
downloadlinux-0b23a1ece9be2c3e04c3b8d3594a1ada1fa1ae50.tar.bz2
dmaengine: idma64: improve residue estimation
The residue calculation may provide a wrong estimation when the transfer is started. There are possible scenarios we have to separate: 1) the transfer is not started yet; residue is equal to the total length; 2) the transfer is just started (first chunk is ongoing); residue is equal to the total length without already transfered bytes; 3) the transfer is ongoing and we already sent few chunks of data; residue is equal to the total length without fully transfered chunks and already sent bytes. Mistakenly the calculation in cases 2) and 3) was done in the similar way and the result is equal to -bytes that have been transfered, i.e. quite big since size_t type can't keep negative values. Rewrite the calculation algorithm to be one pass and have a correct result. Besides above in case user asks for a status of the active DMA descriptor without pausing an ongoing transfer the residue will be estimated based on the register value, though it's still racy. Since the transfer is active the value is continuously being changed. Here we have to read two registers at a time. To minimize an error make those reads close to each other. Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Diffstat (limited to 'drivers/dma/idma64.c')
-rw-r--r--drivers/dma/idma64.c16
1 files changed, 8 insertions, 8 deletions
diff --git a/drivers/dma/idma64.c b/drivers/dma/idma64.c
index 18c14e1f1414..48d6d9e94f67 100644
--- a/drivers/dma/idma64.c
+++ b/drivers/dma/idma64.c
@@ -355,23 +355,23 @@ static size_t idma64_active_desc_size(struct idma64_chan *idma64c)
struct idma64_desc *desc = idma64c->desc;
struct idma64_hw_desc *hw;
size_t bytes = desc->length;
- u64 llp;
- u32 ctlhi;
+ u64 llp = channel_readq(idma64c, LLP);
+ u32 ctlhi = channel_readl(idma64c, CTL_HI);
unsigned int i = 0;
- llp = channel_readq(idma64c, LLP);
do {
hw = &desc->hw[i];
- } while ((hw->llp != llp) && (++i < desc->ndesc));
+ if (hw->llp == llp)
+ break;
+ bytes -= hw->len;
+ } while (++i < desc->ndesc);
if (!i)
return bytes;
- do {
- bytes -= desc->hw[--i].len;
- } while (i);
+ /* The current chunk is not fully transfered yet */
+ bytes += desc->hw[--i].len;
- ctlhi = channel_readl(idma64c, CTL_HI);
return bytes - IDMA64C_CTLH_BLOCK_TS(ctlhi);
}