[PATCH 4.5 028/200] dmaengine: hsu: correct use of channel status register

Greg Kroah-Hartman
2016-05-03T01:23:18Z

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

commit 4f4bc0abff79dc9d7ccbd3143adbf8ad1f4fe6ab upstream.

There is a typo in documentation regarding to descriptor empty bit (DESCE)
which is set to 1 when descriptor is empty. Thus, status register at the end of
a transfer usually returns all DESCE bits set and thus it will never be zero.

Moreover, there are 2 bits (CDESC) that encode current descriptor, on which
interrupt has been asserted. In case when we have few descriptors programmed we
might have non-zero value.

Remove DESCE and CDESC bits from DMA channel status register (HSU_CH_SR) when
reading it.

Fixes: 2b49e0c56741 ("dmaengine: append hsu DMA driver")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/dma/hsu/hsu.c | 2 +-
drivers/dma/hsu/hsu.h | 3 +++
2 files changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/dma/hsu/hsu.c
+++ b/drivers/dma/hsu/hsu.c
@@ -135,7 +135,7 @@ static u32 hsu_dma_chan_get_sr(struct hs
sr = hsu_chan_readl(hsuc, HSU_CH_SR);
spin_unlock_irqrestore(&hsuc->vchan.lock, flags);

- return sr;
+ return sr & ~(HSU_CH_SR_DESCE_ANY | HSU_CH_SR_CDESC_ANY);
}

irqreturn_t hsu_dma_irq(struct hsu_dma_chip *chip, unsigned short nr)
--- a/drivers/dma/hsu/hsu.h
+++ b/drivers/dma/hsu/hsu.h
@@ -41,6 +41,9 @@
#define HSU_CH_SR_DESCTO(x) BIT(8 + (x))
#define HSU_CH_SR_DESCTO_ANY (BIT(11) | BIT(10) | BIT(9) | BIT(8))
#define HSU_CH_SR_CHE BIT(15)
+#define HSU_CH_SR_DESCE(x) BIT(16 + (x))
+#define HSU_CH_SR_DESCE_ANY (BIT(19) | BIT(18) | BIT(17) | BIT(16))
+#define HSU_CH_SR_CDESC_ANY (BIT(31) | BIT(30))

/* Bits in HSU_CH_CR */
#define HSU_CH_CR_CHA BIT(0)