Hi Tomi,
Thank you for the patch.
On Fri, Mar 13, 2020 at 10:26:39AM +0200, Tomi Valkeinen wrote:
> When the CAL driver stops streaming, it will shut everything down
> without waiting for the current frame to finish. This leaves the CAL DMA
> in a slightly undefined state, and when CAL DMA is enabled when the
> stream is started the next time, the old DMA transfer will continue.
>
> It is not clear if the old DMA transfer continues with the exact
> settings of the original transfer, or is it a mix of old and new
> settings, but in any case the end result is memory corruption as the
> destination memory address is no longer valid.
>
> I could not find any way to ensure that any old DMA transfer would be
> discarded, except perhaps full CAL reset. But we cannot do a full reset
> when one port is getting enabled, as that would reset both ports.
>
> This patch tries to make sure that the DMA transfer is finished properly
> when the stream is being stopped. I say "tries", as, as mentioned above,
> I don't see a way to force the DMA transfer to finish. I believe this
> fixes the corruptions for normal cases, but if for some reason the DMA
> of the final frame would stall a lot, resulting in timeout in the code
> waiting for the DMA to finish, we'll again end up with unfinished DMA
> transfer. However, I don't know what could cause such a timeout.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> drivers/media/platform/ti-vpe/cal.c | 32 +++++++++++++++++++++++++++++
> 1 file changed, 32 insertions(+)
>
> diff --git a/drivers/media/platform/ti-vpe/cal.c b/drivers/media/platform/ti-vpe/cal.c
> index be54806180a5..b857cab120ad 100644
> --- a/drivers/media/platform/ti-vpe/cal.c
> +++ b/drivers/media/platform/ti-vpe/cal.c
> @@ -414,6 +414,8 @@ struct cal_ctx {
> struct cal_buffer *cur_frm;
> /* Pointer pointing to next v4l2_buffer */
> struct cal_buffer *next_frm;
> +
> + bool dma_act;
> };
>
> static const struct cal_fmt *find_format_by_pix(struct cal_ctx *ctx,
> @@ -944,6 +946,7 @@ static void csi2_lane_config(struct cal_ctx *ctx)
>
> static void csi2_ppi_enable(struct cal_ctx *ctx)
> {
> + reg_write(ctx->dev, CAL_CSI2_PPI_CTRL(ctx->csi2_port), BIT(3));
> reg_write_field(ctx->dev, CAL_CSI2_PPI_CTRL(ctx->csi2_port),
> CAL_GEN_ENABLE, CAL_CSI2_PPI_CTRL_IF_EN_MASK);
> }
> @@ -1206,15 +1209,25 @@ static irqreturn_t cal_irq(int irq_cal, void *data)
> if (isportirqset(irqst2, 1)) {
> ctx = dev->ctx[0];
>
> + spin_lock(&ctx->slock);
> + ctx->dma_act = false;
> +
> if (ctx->cur_frm != ctx->next_frm)
> cal_process_buffer_complete(ctx);
> +
> + spin_unlock(&ctx->slock);
> }
>
> if (isportirqset(irqst2, 2)) {
> ctx = dev->ctx[1];
>
> + spin_lock(&ctx->slock);
> + ctx->dma_act = false;
> +
> if (ctx->cur_frm != ctx->next_frm)
> cal_process_buffer_complete(ctx);
> +
> + spin_unlock(&ctx->slock);
> }
> }
>
> @@ -1230,6 +1243,7 @@ static irqreturn_t cal_irq(int irq_cal, void *data)
> dma_q = &ctx->vidq;
>
> spin_lock(&ctx->slock);
> + ctx->dma_act = true;
> if (!list_empty(&dma_q->active) &&
> ctx->cur_frm == ctx->next_frm)
> cal_schedule_next_buffer(ctx);
> @@ -1241,6 +1255,7 @@ static irqreturn_t cal_irq(int irq_cal, void *data)
> dma_q = &ctx->vidq;
>
> spin_lock(&ctx->slock);
> + ctx->dma_act = true;
> if (!list_empty(&dma_q->active) &&
> ctx->cur_frm == ctx->next_frm)
> cal_schedule_next_buffer(ctx);
> @@ -1713,10 +1728,27 @@ static void cal_stop_streaming(struct vb2_queue *vq)
> struct cal_ctx *ctx = vb2_get_drv_priv(vq);
> struct cal_dmaqueue *dma_q = &ctx->vidq;
> struct cal_buffer *buf, *tmp;
> + unsigned long timeout;
> unsigned long flags;
> int ret;
> + bool dma_act;
>
> csi2_ppi_disable(ctx);
> +
> + /* wait for stream and dma to finish */
> + dma_act = true;
> + timeout = jiffies + msecs_to_jiffies(500);
> + while (dma_act && time_before(jiffies, timeout)) {
> + msleep(50);
> +
> + spin_lock_irqsave(&ctx->slock, flags);
> + dma_act = ctx->dma_act;
> + spin_unlock_irqrestore(&ctx->slock, flags);
> + }
Waiting for the transfer to complete seems to be a good idea, but how
about using a wait queue instead of such a loop ? That would allow
better usage of CPU time and faster reaction time, and shouldn't be
difficult to implement. You may also want to replace dma_act with a
state if needed (in case you need to express running/stopping/stopped
states), and I would rename it to running if you just need a boolean.
> +
> + if (dma_act)
> + ctx_err(ctx, "failed to disable dma cleanly\n");
> +
> disable_irqs(ctx);
> csi2_phy_deinit(ctx);
>
--
Regards,
Laurent Pinchart
