FAILED: patch "[PATCH] serial: 8250_pxa: Configure tx_loadsz to match FIFO IRQ level" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 5208e7ced520a813b4f4774451fbac4e517e78b2
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024061755-unissued-basically-add8@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

5208e7ced520 ("serial: 8250_pxa: Configure tx_loadsz to match FIFO IRQ level") cc6628f07e0d ("serial: 8250_pxa: Switch to use uart_read_port_properties()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5208e7ced520a813b4f4774451fbac4e517e78b2 Mon Sep 17 00:00:00 2001
From: Doug Brown <[email protected]>
Date: Sun, 19 May 2024 12:19:30 -0700
Subject: [PATCH] serial: 8250_pxa: Configure tx_loadsz to match FIFO IRQ level

The FIFO is 64 bytes, but the FCR is configured to fire the TX interrupt when the FIFO is half empty (bit 3 = 0). Thus, we should only write 32 bytes when a TX interrupt occurs.

This fixes a problem observed on the PXA168 that dropped a bunch of TX bytes during large transmissions.

index f1a51b00b1b9..ba96fa913e7f 100644
@@ -125,6 +125,7 @@ static int serial_pxa_probe(struct platform_device *pdev)
 	uart.port.iotype = UPIO_MEM32;
 	uart.port.regshift = 2;
 	uart.port.fifosize = 64;
+	uart.tx_loadsz = 32;
 	uart.dl_write = serial_pxa_dl_write;
 
 	ret = serial8250_register_8250_port(&uart);

The FIFO is 64 bytes, but the FCR is configured to fire the TX interrupt when the FIFO is half empty (bit 3 = 0). Thus, we should only write 32 bytes when a TX interrupt occurs.

This fixes a problem observed on the PXA168 that dropped a bunch of TX bytes during large transmissions.

---
 drivers/tty/serial/8250/8250_pxa.c | 1 +
 1 file changed, 1 insertion(+)

index 795e55142d4c..70a56062f791 100644
@@ -124,6 +124,7 @@ static int serial_pxa_probe(struct platform_device *pdev)
 	uart.port.regshift = 2;
 	uart.port.irq = irq;
 	uart.port.fifosize = 64;
+	uart.tx_loadsz = 32;
 	uart.port.flags = UPF_IOREMAP | UPF_SKIP_TEST | UPF_FIXED_TYPE;
 	uart.port.dev = &pdev->dev;
 	uart.port.uartclk = clk_get_rate(data->clk);

2.34.1