Preserve the original value of the Divisor Latch Fraction (DLF) register. When the DLF register is modified without preservation, it can disrupt the baudrate settings established by firmware or bootloader, leading to data corruption and the generation of unreadable or distorted characters.
Fixes: 701c5e73b296 ("serial: 8250_dw: add fractional divisor support") Signed-off-by: Ruihong Luo colorsu1922@gmail.com --- v4: * Use the old_dlf to hold the DLF register value
drivers/tty/serial/8250/8250_dwlib.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_dwlib.c b/drivers/tty/serial/8250/8250_dwlib.c index 75f32f054ebb..84843e204a5e 100644 --- a/drivers/tty/serial/8250/8250_dwlib.c +++ b/drivers/tty/serial/8250/8250_dwlib.c @@ -244,7 +244,7 @@ void dw8250_setup_port(struct uart_port *p) struct dw8250_port_data *pd = p->private_data; struct dw8250_data *data = to_dw8250_data(pd); struct uart_8250_port *up = up_to_u8250p(p); - u32 reg; + u32 reg, old_dlf;
pd->hw_rs485_support = dw8250_detect_rs485_hw(p); if (pd->hw_rs485_support) { @@ -270,9 +270,11 @@ void dw8250_setup_port(struct uart_port *p) dev_dbg(p->dev, "Designware UART version %c.%c%c\n", (reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff);
+ /* Preserve value written by firmware or bootloader */ + old_dlf = dw8250_readl_ext(p, DW_UART_DLF); dw8250_writel_ext(p, DW_UART_DLF, ~0U); reg = dw8250_readl_ext(p, DW_UART_DLF); - dw8250_writel_ext(p, DW_UART_DLF, 0); + dw8250_writel_ext(p, DW_UART_DLF, old_dlf);
if (reg) { pd->dlf_size = fls(reg);
Hi,
Thanks for your patch.
FYI: kernel test robot notices the stable kernel rule is not satisfied.
Rule: 'Cc: stable@vger.kernel.org' or 'commit <sha1> upstream.' Subject: [PATCH v4] serial: 8250_dw: Preserve original value of DLF register Link: https://lore.kernel.org/stable/20230713004235.35904-1-colorsu1922%40gmail.co...
The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
On Thu, Jul 13, 2023 at 08:42:36AM +0800, Ruihong Luo wrote:
Preserve the original value of the Divisor Latch Fraction (DLF) register. When the DLF register is modified without preservation, it can disrupt the baudrate settings established by firmware or bootloader, leading to data corruption and the generation of unreadable or distorted characters.
You forgot to add my tag. Why? Do you think the name of variable warrants this? Whatever, Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com
Next time if you don't pick up somebody's tag, care to explain in the changelog why.
Fixes: 701c5e73b296 ("serial: 8250_dw: add fractional divisor support") Signed-off-by: Ruihong Luo colorsu1922@gmail.com
On Thu, 13 Jul 2023, Ruihong Luo wrote:
Preserve the original value of the Divisor Latch Fraction (DLF) register. When the DLF register is modified without preservation, it can disrupt the baudrate settings established by firmware or bootloader, leading to data corruption and the generation of unreadable or distorted characters.
Fixes: 701c5e73b296 ("serial: 8250_dw: add fractional divisor support")
You forgot to add:
Cc: stable@vger.kernel.org
Signed-off-by: Ruihong Luo colorsu1922@gmail.com
Other than that,
Reviewed-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com
On Fri, Jul 14, 2023 at 03:07:42PM +0300, Ilpo Järvinen wrote:
On Thu, 13 Jul 2023, Ruihong Luo wrote:
Preserve the original value of the Divisor Latch Fraction (DLF) register. When the DLF register is modified without preservation, it can disrupt the baudrate settings established by firmware or bootloader, leading to data corruption and the generation of unreadable or distorted characters.
Fixes: 701c5e73b296 ("serial: 8250_dw: add fractional divisor support")
You forgot to add:
Cc: stable@vger.kernel.org
It's there. Just not in the commit message. It's fine.
Signed-off-by: Ruihong Luo colorsu1922@gmail.com
Other than that,
Reviewed-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com
On Fri, Jul 14, 2023 at 03:31:11PM +0300, Andy Shevchenko wrote:
On Fri, Jul 14, 2023 at 03:07:42PM +0300, Ilpo Järvinen wrote:
On Thu, 13 Jul 2023, Ruihong Luo wrote:
Preserve the original value of the Divisor Latch Fraction (DLF) register. When the DLF register is modified without preservation, it can disrupt the baudrate settings established by firmware or bootloader, leading to data corruption and the generation of unreadable or distorted characters.
Fixes: 701c5e73b296 ("serial: 8250_dw: add fractional divisor support")
You forgot to add:
Cc: stable@vger.kernel.org
It's there. Just not in the commit message. It's fine.
No it isn't, that's not how to have a patch added to the stable tree, as my form letter says:
<formletter>
This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.
</formletter>
I'll go fix it up by hand...
On Tue, Jul 25, 2023 at 08:31:17PM +0200, Greg Kroah-Hartman wrote:
On Fri, Jul 14, 2023 at 03:31:11PM +0300, Andy Shevchenko wrote:
On Fri, Jul 14, 2023 at 03:07:42PM +0300, Ilpo Järvinen wrote:
On Thu, 13 Jul 2023, Ruihong Luo wrote:
Preserve the original value of the Divisor Latch Fraction (DLF) register. When the DLF register is modified without preservation, it can disrupt the baudrate settings established by firmware or bootloader, leading to data corruption and the generation of unreadable or distorted characters.
Fixes: 701c5e73b296 ("serial: 8250_dw: add fractional divisor support")
You forgot to add:
Cc: stable@vger.kernel.org
It's there. Just not in the commit message. It's fine.
No it isn't, that's not how to have a patch added to the stable tree, as my form letter says:
<formletter>
This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.
</formletter>
I'll go fix it up by hand...
Good to know, thank you for the clarification!
linux-stable-mirror@lists.linaro.org
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Andy Shevchenko -
Greg Kroah-Hartman -
Ilpo Järvinen -
kernel test robot -
Ruihong Luo