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serial: 8250_dw: Decouple DLF register check from UCV 

Designware UART has an optional feature to enable Fractional Baud Rate
Divisor (DLF) through the FRACTIONAL_BAUD_DIVISOR_EN configuration
parameter, and it is not dependent on ADDITIONAL_FEATURES.

dw8250_setup_port() checks DLF to determine dlf_size only when UART
Component Version (UCV) is non-zero. As mentioned above DLF and UCV are
independent features. Move the logic corresponding to DLF size
calculation ahead of the UCV check to prevent early return. Otherwise,
dlf_size will be zero and driver will not be able to use the
controller's fractional baud rate divisor (DLF) feature.

Signed-off-by: Vamshi Gajjela <vamshigajjela@google.com>
Link: https://lore.kernel.org/r/20231126160420.2442330-1-vamshigajjela@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Vamshi Gajjela 2023-11-26 21:34:20 +05:30 committed by Greg Kroah-Hartman
parent 068ab2135b
commit d804987153
1 changed files with 11 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
drivers/tty/serial/8250/8250_dwlib.c
View File

@ -259,17 +259,6 @@ void dw8250_setup_port(struct uart_port *p)
}
up->capabilities |= UART_CAP_NOTEMT;
/*
* If the Component Version Register returns zero, we know that
* ADDITIONAL_FEATURES are not enabled. No need to go any further.
*/
reg = dw8250_readl_ext(p, DW_UART_UCV);
if (!reg)
return;
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);
@ -282,6 +271,17 @@ void dw8250_setup_port(struct uart_port *p)
p->set_divisor = dw8250_set_divisor;
}
/*
* If the Component Version Register returns zero, we know that
* ADDITIONAL_FEATURES are not enabled. No need to go any further.
*/
reg = dw8250_readl_ext(p, DW_UART_UCV);
if (!reg)
return;
dev_dbg(p->dev, "Designware UART version %c.%c%c\n",
(reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff);
reg = dw8250_readl_ext(p, DW_UART_CPR);
if (!reg) {
reg = data->pdata->cpr_val;