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[PATCH 1/2] drm/bridge: samsung-dsim: use while loop in samsung_dsim_transfer_start

Philipp Zabel posted 2 patches 6 months, 3 weeks ago
[PATCH 1/2] drm/bridge: samsung-dsim: use while loop in samsung_dsim_transfer_start
Posted by Philipp Zabel 6 months, 3 weeks ago 
Turn the open-coded goto-again construct into a while loop, to make
samsung_dsim_transfer_start() a bit shorter and easier to read.

Hold the spinlock when looping back around and avoid the duplicated
list_empty() check.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 51 +++++++++++++++--------------------
 1 file changed, 21 insertions(+), 30 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 0014c497e3fe7d8349a119dbdda30d65d816cccf..1dfc9710bee5134e0e0114ce52f673c21564b11b 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1235,43 +1235,34 @@ static void samsung_dsim_transfer_start(struct samsung_dsim *dsi)
 {
 	unsigned long flags;
 	struct samsung_dsim_transfer *xfer;
-	bool start = false;
 
-again:
 	spin_lock_irqsave(&dsi->transfer_lock, flags);
 
-	if (list_empty(&dsi->transfer_list)) {
+	while (!list_empty(&dsi->transfer_list)) {
+		xfer = list_first_entry(&dsi->transfer_list,
+					struct samsung_dsim_transfer, list);
+
 		spin_unlock_irqrestore(&dsi->transfer_lock, flags);
-		return;
+
+		if (xfer->packet.payload_length &&
+		    xfer->tx_done == xfer->packet.payload_length)
+			/* waiting for RX */
+			return;
+
+		samsung_dsim_send_to_fifo(dsi, xfer);
+
+		if (xfer->packet.payload_length || xfer->rx_len)
+			return;
+
+		xfer->result = 0;
+		complete(&xfer->completed);
+
+		spin_lock_irqsave(&dsi->transfer_lock, flags);
+
+		list_del_init(&xfer->list);
 	}
 
-	xfer = list_first_entry(&dsi->transfer_list,
-				struct samsung_dsim_transfer, list);
-
 	spin_unlock_irqrestore(&dsi->transfer_lock, flags);
-
-	if (xfer->packet.payload_length &&
-	    xfer->tx_done == xfer->packet.payload_length)
-		/* waiting for RX */
-		return;
-
-	samsung_dsim_send_to_fifo(dsi, xfer);
-
-	if (xfer->packet.payload_length || xfer->rx_len)
-		return;
-
-	xfer->result = 0;
-	complete(&xfer->completed);
-
-	spin_lock_irqsave(&dsi->transfer_lock, flags);
-
-	list_del_init(&xfer->list);
-	start = !list_empty(&dsi->transfer_list);
-
-	spin_unlock_irqrestore(&dsi->transfer_lock, flags);
-
-	if (start)
-		goto again;
 }
 
 static bool samsung_dsim_transfer_finish(struct samsung_dsim *dsi)

-- 
2.39.5
Re: [PATCH 1/2] drm/bridge: samsung-dsim: use while loop in samsung_dsim_transfer_start
Posted by Frieder Schrempf 6 months, 3 weeks ago 
Am 27.05.25 um 16:21 schrieb Philipp Zabel:
> Turn the open-coded goto-again construct into a while loop, to make
> samsung_dsim_transfer_start() a bit shorter and easier to read.
> 
> Hold the spinlock when looping back around and avoid the duplicated
> list_empty() check.
> 
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>

> ---
>  drivers/gpu/drm/bridge/samsung-dsim.c | 51 +++++++++++++++--------------------
>  1 file changed, 21 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> index 0014c497e3fe7d8349a119dbdda30d65d816cccf..1dfc9710bee5134e0e0114ce52f673c21564b11b 100644
> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> @@ -1235,43 +1235,34 @@ static void samsung_dsim_transfer_start(struct samsung_dsim *dsi)
>  {
>  	unsigned long flags;
>  	struct samsung_dsim_transfer *xfer;
> -	bool start = false;
>  
> -again:
>  	spin_lock_irqsave(&dsi->transfer_lock, flags);
>  
> -	if (list_empty(&dsi->transfer_list)) {
> +	while (!list_empty(&dsi->transfer_list)) {
> +		xfer = list_first_entry(&dsi->transfer_list,
> +					struct samsung_dsim_transfer, list);
> +
>  		spin_unlock_irqrestore(&dsi->transfer_lock, flags);
> -		return;
> +
> +		if (xfer->packet.payload_length &&
> +		    xfer->tx_done == xfer->packet.payload_length)
> +			/* waiting for RX */
> +			return;
> +
> +		samsung_dsim_send_to_fifo(dsi, xfer);
> +
> +		if (xfer->packet.payload_length || xfer->rx_len)
> +			return;
> +
> +		xfer->result = 0;
> +		complete(&xfer->completed);
> +
> +		spin_lock_irqsave(&dsi->transfer_lock, flags);
> +
> +		list_del_init(&xfer->list);
>  	}
>  
> -	xfer = list_first_entry(&dsi->transfer_list,
> -				struct samsung_dsim_transfer, list);
> -
>  	spin_unlock_irqrestore(&dsi->transfer_lock, flags);
> -
> -	if (xfer->packet.payload_length &&
> -	    xfer->tx_done == xfer->packet.payload_length)
> -		/* waiting for RX */
> -		return;
> -
> -	samsung_dsim_send_to_fifo(dsi, xfer);
> -
> -	if (xfer->packet.payload_length || xfer->rx_len)
> -		return;
> -
> -	xfer->result = 0;
> -	complete(&xfer->completed);
> -
> -	spin_lock_irqsave(&dsi->transfer_lock, flags);
> -
> -	list_del_init(&xfer->list);
> -	start = !list_empty(&dsi->transfer_list);
> -
> -	spin_unlock_irqrestore(&dsi->transfer_lock, flags);
> -
> -	if (start)
> -		goto again;
>  }
>  
>  static bool samsung_dsim_transfer_finish(struct samsung_dsim *dsi)
>
Re: [PATCH 1/2] drm/bridge: samsung-dsim: use while loop in samsung_dsim_transfer_start
Posted by Alexander Stein 6 months, 3 weeks ago 
Am Dienstag, 27. Mai 2025, 16:21:47 CEST schrieb Philipp Zabel:
> Turn the open-coded goto-again construct into a while loop, to make
> samsung_dsim_transfer_start() a bit shorter and easier to read.
> 
> Hold the spinlock when looping back around and avoid the duplicated
> list_empty() check.
> 
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>

> ---
>  drivers/gpu/drm/bridge/samsung-dsim.c | 51 +++++++++++++++--------------------
>  1 file changed, 21 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> index 0014c497e3fe7d8349a119dbdda30d65d816cccf..1dfc9710bee5134e0e0114ce52f673c21564b11b 100644
> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> @@ -1235,43 +1235,34 @@ static void samsung_dsim_transfer_start(struct samsung_dsim *dsi)
>  {
>  	unsigned long flags;
>  	struct samsung_dsim_transfer *xfer;
> -	bool start = false;
>  
> -again:
>  	spin_lock_irqsave(&dsi->transfer_lock, flags);
>  
> -	if (list_empty(&dsi->transfer_list)) {
> +	while (!list_empty(&dsi->transfer_list)) {
> +		xfer = list_first_entry(&dsi->transfer_list,
> +					struct samsung_dsim_transfer, list);
> +
>  		spin_unlock_irqrestore(&dsi->transfer_lock, flags);
> -		return;
> +
> +		if (xfer->packet.payload_length &&
> +		    xfer->tx_done == xfer->packet.payload_length)
> +			/* waiting for RX */
> +			return;
> +
> +		samsung_dsim_send_to_fifo(dsi, xfer);
> +
> +		if (xfer->packet.payload_length || xfer->rx_len)
> +			return;
> +
> +		xfer->result = 0;
> +		complete(&xfer->completed);
> +
> +		spin_lock_irqsave(&dsi->transfer_lock, flags);
> +
> +		list_del_init(&xfer->list);
>  	}
>  
> -	xfer = list_first_entry(&dsi->transfer_list,
> -				struct samsung_dsim_transfer, list);
> -
>  	spin_unlock_irqrestore(&dsi->transfer_lock, flags);
> -
> -	if (xfer->packet.payload_length &&
> -	    xfer->tx_done == xfer->packet.payload_length)
> -		/* waiting for RX */
> -		return;
> -
> -	samsung_dsim_send_to_fifo(dsi, xfer);
> -
> -	if (xfer->packet.payload_length || xfer->rx_len)
> -		return;
> -
> -	xfer->result = 0;
> -	complete(&xfer->completed);
> -
> -	spin_lock_irqsave(&dsi->transfer_lock, flags);
> -
> -	list_del_init(&xfer->list);
> -	start = !list_empty(&dsi->transfer_list);
> -
> -	spin_unlock_irqrestore(&dsi->transfer_lock, flags);
> -
> -	if (start)
> -		goto again;
>  }
>  
>  static bool samsung_dsim_transfer_finish(struct samsung_dsim *dsi)
> 
> 


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