[alsa-devel] [PATCH 0/2] OMAP2+: DMA: fix src/dst position reporting
Hello,
If the user asks for the sDMA current position before the first data has been transmitted (before the first DMA request has been generated), the reported position is not valid: src position: CSAC is uninitialized dst position: CDAC is 0
The return values in both case considered invalid. This sitation can be identified by checking if the CDAC register is 0 (it is initialized to 0 in omap_dam_start call). In this case return the programmed source/destination address.
The affected omap_get_dma_src_pos/omap_get_dma_dst_pos functions are used by the audio stack mainly for checking the current position of the audio stream.
Regards, Peter --- Peter Ujfalusi (2): OMAP2+: DMA: Workaround for invalid source position OMAP2+: DMA: Workaround for invalid destination position
arch/arm/plat-omap/dma.c | 25 ++++++++++++++++++++++--- 1 files changed, 22 insertions(+), 3 deletions(-)
If the DMA source position has been asked before the first actual data transfer has been done, the CSAC register does not contain valid information. We can identify this situation by checking the CDAC register: CDAC != 0 indicates that the DMA transfer on the channel has been started already. When CDAC == 0 we can not trust the CSAC value since it has not been updated, and can contain random number. Return the start address in case the DMA has not jet started.
Note: The CDAC register has been initialized to 0 at dma_start time.
Signed-off-by: Peter Ujfalusi peter.ujfalusi@ti.com --- arch/arm/plat-omap/dma.c | 15 +++++++++++++-- 1 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c index c22217c..38b0d44 100644 --- a/arch/arm/plat-omap/dma.c +++ b/arch/arm/plat-omap/dma.c @@ -1024,12 +1024,23 @@ EXPORT_SYMBOL(omap_set_dma_callback); */ dma_addr_t omap_get_dma_src_pos(int lch) { + u32 cdac; dma_addr_t offset = 0;
if (cpu_is_omap15xx()) offset = p->dma_read(CPC, lch); - else - offset = p->dma_read(CSAC, lch); + else { + /* + * CDAC == 0 indicates that the DMA transfer on the channel has + * not been started (no data has been transferred so far). + * Return the programmed source start address in this case. + */ + cdac = p->dma_read(CDAC, lch); + if (likely(cdac)) + offset = p->dma_read(CSAC, lch); + else + offset = p->dma_read(CSSA, lch); + }
if (IS_DMA_ERRATA(DMA_ERRATA_3_3) && offset == 0) offset = p->dma_read(CSAC, lch);
* Peter Ujfalusi peter.ujfalusi@ti.com [111031 06:46]:
If the DMA source position has been asked before the first actual data transfer has been done, the CSAC register does not contain valid information. We can identify this situation by checking the CDAC register: CDAC != 0 indicates that the DMA transfer on the channel has been started already. When CDAC == 0 we can not trust the CSAC value since it has not been updated, and can contain random number. Return the start address in case the DMA has not jet started.
Note: The CDAC register has been initialized to 0 at dma_start time.
Signed-off-by: Peter Ujfalusi peter.ujfalusi@ti.com
arch/arm/plat-omap/dma.c | 15 +++++++++++++-- 1 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c index c22217c..38b0d44 100644 --- a/arch/arm/plat-omap/dma.c +++ b/arch/arm/plat-omap/dma.c @@ -1024,12 +1024,23 @@ EXPORT_SYMBOL(omap_set_dma_callback); */ dma_addr_t omap_get_dma_src_pos(int lch) {
u32 cdac; dma_addr_t offset = 0;
if (cpu_is_omap15xx()) offset = p->dma_read(CPC, lch);
- else
offset = p->dma_read(CSAC, lch);
else {
/** CDAC == 0 indicates that the DMA transfer on the channel has* not been started (no data has been transferred so far).* Return the programmed source start address in this case.*/cdac = p->dma_read(CDAC, lch);if (likely(cdac))offset = p->dma_read(CSAC, lch);elseoffset = p->dma_read(CSSA, lch);}
if (IS_DMA_ERRATA(DMA_ERRATA_3_3) && offset == 0) offset = p->dma_read(CSAC, lch);
Should these tests be done only after the errata re-read for both src and dst patches? Otherwise the errata will not be handled?
Tony
* Tony Lindgren tony@atomide.com [111103 13:53]:
- Peter Ujfalusi peter.ujfalusi@ti.com [111031 06:46]:
If the DMA source position has been asked before the first actual data transfer has been done, the CSAC register does not contain valid information. We can identify this situation by checking the CDAC register: CDAC != 0 indicates that the DMA transfer on the channel has been started already. When CDAC == 0 we can not trust the CSAC value since it has not been updated, and can contain random number. Return the start address in case the DMA has not jet started.
Note: The CDAC register has been initialized to 0 at dma_start time.
Signed-off-by: Peter Ujfalusi peter.ujfalusi@ti.com
arch/arm/plat-omap/dma.c | 15 +++++++++++++-- 1 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c index c22217c..38b0d44 100644 --- a/arch/arm/plat-omap/dma.c +++ b/arch/arm/plat-omap/dma.c @@ -1024,12 +1024,23 @@ EXPORT_SYMBOL(omap_set_dma_callback); */ dma_addr_t omap_get_dma_src_pos(int lch) {
u32 cdac; dma_addr_t offset = 0;
if (cpu_is_omap15xx()) offset = p->dma_read(CPC, lch);
- else
offset = p->dma_read(CSAC, lch);
else {
/** CDAC == 0 indicates that the DMA transfer on the channel has* not been started (no data has been transferred so far).* Return the programmed source start address in this case.*/cdac = p->dma_read(CDAC, lch);if (likely(cdac))offset = p->dma_read(CSAC, lch);elseoffset = p->dma_read(CSSA, lch);}
if (IS_DMA_ERRATA(DMA_ERRATA_3_3) && offset == 0) offset = p->dma_read(CSAC, lch);
Should these tests be done only after the errata re-read for both src and dst patches? Otherwise the errata will not be handled?
Also, please Cc linux-arm-kernel list too so I don't have to repost :)
Tony
If the DMA destination position has been asked before the first actual data transfer has been done, the CDAC register still contains 0 (it is initialized to 0 at omsp_dma_start). If CDAC == 0, return the programmed start address.
Signed-off-by: Peter Ujfalusi peter.ujfalusi@ti.com --- arch/arm/plat-omap/dma.c | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c index 38b0d44..9186491 100644 --- a/arch/arm/plat-omap/dma.c +++ b/arch/arm/plat-omap/dma.c @@ -1066,8 +1066,16 @@ dma_addr_t omap_get_dma_dst_pos(int lch)
if (cpu_is_omap15xx()) offset = p->dma_read(CPC, lch); - else + else { offset = p->dma_read(CDAC, lch); + /* + * CDAC == 0 indicates that the DMA transfer on the channel has + * not been started (no data has been transferred so far). + * Return the programmed destination start address in this case. + */ + if (unlikely(!offset)) + offset = p->dma_read(CDSA, lch); + }
/* * omap 3.2/3.3 erratum: sometimes 0 is returned if CSAC/CDAC is
On 10/31/2011 04:20 PM, Peter Ujfalusi wrote:
Hello,
If the user asks for the sDMA current position before the first data has been transmitted (before the first DMA request has been generated), the reported position is not valid: src position: CSAC is uninitialized dst position: CDAC is 0
The return values in both case considered invalid. This sitation can be identified by checking if the CDAC register is 0 (it is initialized to 0 in omap_dam_start call). In this case return the programmed source/destination address.
The affected omap_get_dma_src_pos/omap_get_dma_dst_pos functions are used by the audio stack mainly for checking the current position of the audio stream.
Regards, Peter
Peter Ujfalusi (2): OMAP2+: DMA: Workaround for invalid source position OMAP2+: DMA: Workaround for invalid destination position
arch/arm/plat-omap/dma.c | 25 ++++++++++++++++++++++--- 1 files changed, 22 insertions(+), 3 deletions(-)
Both,
Reviewed-by: Jarkko Nikula jarkko.nikula@bitmer.com
participants (3)
-
Jarkko Nikula -
Peter Ujfalusi -
Tony Lindgren