From: Rabin Vincent <[email protected]> Hardware bug: when a logical channel is triggerred by a high priority destination event line, an extra packet transaction is generated in case of important data write response latency on previous logical channel A and if the source transfer of current logical channel B is already completed and if no other channel with a higher priority than B is waiting for execution.
Software workaround: do not set the high priority level for the destination event lines that trigger logical channels. Signed-off-by: Rabin Vincent <[email protected]> Reviewed-by: Shreshtha Kumar Sahu <[email protected]> Acked-by: Linus Walleij <[email protected]> Signed-off-by: Fabio Baltieri <[email protected]> --- drivers/dma/ste_dma40.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c index 760576b..9f8964a 100644 --- a/drivers/dma/ste_dma40.c +++ b/drivers/dma/ste_dma40.c @@ -2180,11 +2180,24 @@ static void __d40_set_prio_rt(struct d40_chan *d40c, int dev_type, bool src) { bool realtime = d40c->dma_cfg.realtime; bool highprio = d40c->dma_cfg.high_priority; - u32 prioreg = highprio ? D40_DREG_PSEG1 : D40_DREG_PCEG1; u32 rtreg = realtime ? D40_DREG_RSEG1 : D40_DREG_RCEG1; u32 event = D40_TYPE_TO_EVENT(dev_type); u32 group = D40_TYPE_TO_GROUP(dev_type); u32 bit = 1 << event; + u32 prioreg; + + /* + * Due to a hardware bug, in some cases a logical channel triggered by + * a high priority destination event line can generate extra packet + * transactions. + * + * The workaround is to not set the high priority level for the + * destination event lines that trigger logical channels. + */ + if (!src && chan_is_logical(d40c)) + highprio = false; + + prioreg = highprio ? D40_DREG_PSEG1 : D40_DREG_PCEG1; /* Destination event lines are stored in the upper halfword */ if (!src) -- 1.7.12.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
