linux-kernel - Re: [PATCH v5 2/2] serial:sunplus-uart:Add Sunplus SoC UART Driver

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Message-ID: <YcGOmzKSHOoycZNC@kroah.com>
Date:   Tue, 21 Dec 2021 09:21:47 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     hammer hsieh <hammerh0314@...il.com>
Cc:     robh+dt@...nel.org, linux-serial@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        jirislaby@...nel.org, p.zabel@...gutronix.de, wells.lu@...plus.com,
        Hammer Hsieh <hammer.hsieh@...plus.com>
Subject: Re: [PATCH v5 2/2] serial:sunplus-uart:Add Sunplus SoC UART Driver

On Tue, Dec 21, 2021 at 04:14:16PM +0800, hammer hsieh wrote:
> Greg KH <gregkh@...uxfoundation.org> 於 2021年12月20日 週一 下午11:51寫道：
> >
> > On Mon, Dec 13, 2021 at 03:10:07PM +0800, Hammer Hsieh wrote:
> > > +/* Register offsets */
> > > +#define SUP_UART_DATA                        0x00
> > > +#define SUP_UART_LSR                 0x04
> > > +#define SUP_UART_MSR                 0x08
> > > +#define SUP_UART_LCR                 0x0C
> > > +#define SUP_UART_MCR                 0x10
> > > +#define SUP_UART_DIV_L                       0x14
> > > +#define SUP_UART_DIV_H                       0x18
> > > +#define SUP_UART_ISC                 0x1C
> > > +#define SUP_UART_TX_RESIDUE          0x20
> > > +#define SUP_UART_RX_RESIDUE          0x24
> > > +
> > > +/* Line Status Register bits */
> > > +#define SUP_UART_LSR_TXE             BIT(6) /* tx empty */
> > > +#define SUP_UART_LSR_BC                      BIT(5) /* break condition status */
> > > +#define SUP_UART_LSR_FE                      BIT(4) /* frame error status */
> > > +#define SUP_UART_LSR_OE                      BIT(3) /* overrun error status */
> > > +#define SUP_UART_LSR_PE                      BIT(2) /* parity error status */
> > > +#define SUP_UART_LSR_RX                      BIT(1) /* 1: receive fifo not empty */
> > > +#define SUP_UART_LSR_TX                      BIT(0) /* 1: transmit fifo is not full */
> > > +#define SUP_UART_LSR_TX_NOT_FULL     1
> > > +#define SUP_UART_LSR_BRK_ERROR_BITS  GENMASK(5, 2)
> > > +
> > > +/* Line Control Register bits */
> > > +#define SUP_UART_LCR_BC                      BIT(5) /* break condition select */
> > > +#define SUP_UART_LCR_PR                      BIT(4) /* parity bit polarity select */
> > > +#define SUP_UART_LCR_PE                      BIT(3) /* parity bit enable */
> > > +#define SUP_UART_LCR_ST                      BIT(2) /* stop bits select */
> > > +#define SUP_UART_LCR_WL5             0x00 /*  word length 5 */
> > > +#define SUP_UART_LCR_WL6             0x01 /*  word length 6 */
> > > +#define SUP_UART_LCR_WL7             0x02 /*  word length 7 */
> > > +#define SUP_UART_LCR_WL8             0x03 /*  word length 8 (default) */
> > > +
> > > +/* Modem Control Register bits */
> > > +#define SUP_UART_MCR_LB                      BIT(4) /* Loopback mode */
> > > +#define SUP_UART_MCR_RI                      BIT(3) /* ring indicator */
> > > +#define SUP_UART_MCR_DCD             BIT(2) /* data carrier detect */
> > > +#define SUP_UART_MCR_RTS             BIT(1) /* request to send */
> > > +#define SUP_UART_MCR_DTS             BIT(0) /* data terminal ready */
> > > +
> > > +/* Interrupt Status/Control Register bits */
> > > +#define SUP_UART_ISC_RXM             BIT(5) /* RX interrupt enable */
> > > +#define SUP_UART_ISC_TXM             BIT(4) /* TX interrupt enable */
> > > +#define SUP_UART_ISC_RX                      BIT(1) /* RX interrupt status */
> > > +#define SUP_UART_ISC_TX                      BIT(0) /* TX interrupt status */
> > > +
> > > +#define SUP_DUMMY_READ                       BIT(16) /* drop bytes received on a !CREAD port */
> > > +#define SUP_UART_NR                  5
> >
> > Aren't most of these defines already in the kernel header files?  Why
> > create them again?
> >
> 
> If for reduce code.
> I can add #include<linux/serial_reg.h>
> And remove some overlap define name.
> 
> #define SUP_UART_LCR_PR -> UART_LCR_EPAR
> #define SUP_UART_LCR_PE -> UART_LCR_PARITY
> #define SUP_UART_LCR_ST -> UART_LCR_STOP
> #define SUP_UART_LCR_WL5 -> UART_LCR_WLEN5
> #define SUP_UART_LCR_WL6 -> UART_LCR_WLEN6
> #define SUP_UART_LCR_WL7 -> UART_LCR_WLEN7
> #define SUP_UART_LCR_WL8 -> UART_LCR_WLEN8
> 
> #define SUP_UART_MCR_LB -> UART_MCR_LOOP
> #define SUP_UART_MCR_RI -> UART_MCR_OUT2 ?
> #define SUP_UART_MCR_DCD -> UART_MCR_OUT1 ?
> #define SUP_UART_MCR_RTS -> UART_MCR_RTS
> #define SUP_UART_MCR_DTS -> UART_MCR_DTR
> 
> But the rest define didn't match internal #include<linux/serial_reg.h>
> , those define still need to keep.
> Some use SUP_xxxx specific define.
> Some use internal #include<linux/serial_reg.h>, it is strange.

Do not duplicate defines that we already have for the same hardware
type.

And again, why is this not a normal serial driver for the existing UART
types as this hardware is obviously an 8250 variant?

thanks,

greg k-h