[PATCH 6/7] dmaengine: ste_dma40: don't allow high priority dest event lines
From: Rabin Vincent 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 Reviewed-by: Shreshtha Kumar Sahu Acked-by: Linus Walleij Signed-off-by: Fabio Baltieri --- 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 d8d58d9..f871df6 100644 --- a/drivers/dma/ste_dma40.c +++ b/drivers/dma/ste_dma40.c @@ -2181,11 +2181,24 @@ 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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 6/7] dmaengine: ste_dma40: don't allow high priority dest event lines
From: Rabin Vincent rabin.vinc...@stericsson.com 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 rabin.vinc...@stericsson.com Reviewed-by: Shreshtha Kumar Sahu shreshthakumar.s...@stericsson.com Acked-by: Linus Walleij linus.wall...@linaro.org Signed-off-by: Fabio Baltieri fabio.balti...@linaro.org --- 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 d8d58d9..f871df6 100644 --- a/drivers/dma/ste_dma40.c +++ b/drivers/dma/ste_dma40.c @@ -2181,11 +2181,24 @@ 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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/