linux/drivers/dma/sh
Yoshihiro Shimoda 218c21043d dmaengine: sh: rcar-dmac: Should not stop the DMAC by rcar_dmac_sync_tcr()
rcar_dmac_chan_get_residue() should not stop the DMAC, because
the commit 538603c602 ("dmaengine: sh: rcar-dmac: avoid to write
CHCR.TE to 1 if TCR is set to 0") had fixed unexpected re-transferring
issue. But it had caused the next issue which might stop the cyclic
mode transferring. Thus, for example R-Car sound might be stopped
suddenly.

According to the commit 73a47bd0da ("dmaengine: rcar-dmac: use TCRB
instead of TCR for residue"), the purpose of clearing CHCR.DE bit is
flushing buffered data to calculate the exact residue.

Such the "exact" residue had been required by sh-sci driver. sh-sci
driver is calling dmaengine_pause() to stop transferring, and get
"exact" residue. Otherwise, it might receive extra data during
getting residue without pausing.

In rx_timer_fn() of sh-sci driver:
	dmaengine_tx_status();		/* For checking roughly */
 	dmaengine_pause();
	dmaengine_tx_status();		/* For getting residue */
	dmaengine_terminate_all();

But, unfortunately the rcar-dmac driver didn't support dmaengine_pause()
at that time. So, the sh-sci driver cannot get the "exact" residue
without stopping the transferring, because rcar-dmac is buffering data
inside.

Because of these backgrounds, rcar-dmac had been cleared/set CHCR.DE
bit in rcar_dmac_chan_get_residue() to synchronizing data and getting
"exact" residue.

However, rcar-dmac driver has rcar_dmac_chan_pause() now, and clearing
CHCR.DE bit in rcar_dmac_chan_get_residue() doesn't need anymore.
So, this patch removes the rcar_dmac_sync_tcr().

Fixes: 73a47bd0da ("dmaengine: rcar-dmac: use TCRB instead of TCR for residue")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
2018-07-31 09:57:27 +05:30
..
Kconfig dmaengine: sh: Use ARCH_RENESAS 2016-02-08 08:48:08 +05:30
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
rcar-dmac.c dmaengine: sh: rcar-dmac: Should not stop the DMAC by rcar_dmac_sync_tcr() 2018-07-31 09:57:27 +05:30
shdma-arm.h dmaengine: shdma: Use defines instead of hardcoded numbers 2014-07-15 18:02:29 +09:00
shdma-base.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
shdma-of.c dmaengine: Remove .owner field for driver 2014-11-06 11:54:18 +05:30
shdma-r8a73a4.c dmaengine: shdma: r8a73a4: Make dma_ts_shift[] static 2015-05-25 22:33:07 +05:30
shdma.h dmaengine: sh: Rework Kconfig and Makefile 2014-07-31 17:15:45 +05:30
shdmac.c dmaengine: shdmac: Change platform check to CONFIG_ARCH_RENESAS 2018-04-25 14:48:30 +05:30
sudmac.c dmaengine: Remove site specific OOM error messages on kzalloc 2016-06-21 21:35:00 +05:30
usb-dmac.c treewide: Use struct_size() for kmalloc()-family 2018-06-06 11:15:43 -07:00