RE: [PATCH v5 1/3] dmaengine: imx-sdma: fix buffer ownership
From: Robin Gong <hidden>
Date: 2019-12-04 09:20:04
Also in:
dmaengine, lkml
On 2019-9-23 Philipp Puschmann [off-list ref] wrote:
BD_DONE flag marks ownership of the buffer. When 1 SDMA owns the buffer, when 0 ARM owns it. When processing the buffers in sdma_update_channel_loop the ownership of the currently processed buffer was set to SDMA again before running the callback function of the buffer and while the sdma script may be running in parallel. So there was the possibility to get the buffer overwritten by SDMA before it has been processed by kernel
Does this patch need indeed? I don't think any difference here move done flag before callback or after callback, because callback never care this flag and actually done flag is setup for next time rather than this time. Basically, this flag should be set to 1 quickly asap so that sdma could use this bd asap. If delay the flag may cause sdma channel stop since all BDs consumed. Could you try again your case without this patch?
quoted hunk ↗ jump to hunk
leading to kind of random errors in the upper layers, e.g. bluetooth. Fixes: 1ec1e82f2510 ("dmaengine: Add Freescale i.MX SDMA support") Signed-off-by: Philipp Puschmann <redacted> --- Changelog v5: - no changes Changelog v4: - fixed the fixes tag Changelog v3: - use correct dma_wmb() instead of dma_wb() - add fixes tag Changelog v2: - add dma_wb() drivers/dma/imx-sdma.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c index9ba74ab7e912..b42281604e54 100644--- a/drivers/dma/imx-sdma.c +++ b/drivers/dma/imx-sdma.c@@ -802,7 +802,6 @@ static void sdma_update_channel_loop(structsdma_channel *sdmac) */ desc->chn_real_count = bd->mode.count; - bd->mode.status |= BD_DONE; bd->mode.count = desc->period_len; desc->buf_ptail = desc->buf_tail; desc->buf_tail = (desc->buf_tail + 1) % desc->num_bd; @@ -817,6 +816,9 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac) dmaengine_desc_get_callback_invoke(&desc->vd.tx, NULL); spin_lock(&sdmac->vc.lock); + dma_wmb(); + bd->mode.status |= BD_DONE; + if (error) sdmac->status = old_status; } -- 2.23.0
_______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel