HI Ilpo,
Thanks for the feedback.
> Subject: Re: [PATCH v3 3/3] serial: 8250_em: Add serial_out() to struct
> serial8250_em_hw_info
>
> On Fri, 10 Feb 2023, Biju Das wrote:
>
> > As per HW manual section 40.6.1, we need to perform FIFO reset + SW
> > reset before updating the below registers.
> >
> > FCR[7:5], FCR[3:0], LCR[7][5:0], MCR[6:4], DLL[7:0], DLM[7:0] and
> > HCR0[6:5][3:2].
> >
> > This patch adds serial_out() to struct serial8250_em_hw_info to handle
> > this difference between emma mobile and rz/v2m.
> >
> > DLL/DLM register can be updated only by setting LCR[7]. So the
> > updation of LCR[7] will perform reset for DLL/DLM register changes.
> >
> > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> > ---
> > v2->v3:
> > * Replaced readl/writel()->serial8250_em_serial_in/out() in
> serial8250_rzv2m_
> > reg_update() to avoid duplication of offset trickery.
> > * Added support for HCR0 read/write in serial8250_em_{serial_in,
> > serial_out}
> > * Added UART_LCR macro support in serial8250_em_serial_in() to read
> > LCR
> > * Reordered serial8250_em_{serial_in, serial_out} above serial8250_rzv2m_
> > reg_update().
> > * Replaced priv->info->serial_out to info->serial_out.
> > v1->v2:
> > * Added serial_out to struct serial8250_em_hw_info
> > ---
> > drivers/tty/serial/8250/8250_em.c | 67
> > ++++++++++++++++++++++++++++++-
> > 1 file changed, 66 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/tty/serial/8250/8250_em.c
> > b/drivers/tty/serial/8250/8250_em.c
> > index 69cd3b611501..a90a5cc4234a 100644
> > --- a/drivers/tty/serial/8250/8250_em.c
> > +++ b/drivers/tty/serial/8250/8250_em.c
> > @@ -19,10 +19,14 @@
> >
> > #define UART_DLL_EM 9
> > #define UART_DLM_EM 10
> > +#define UART_HCR0 11
> > +
> > +#define UART_HCR0_SW_RESET BIT(7) /* SW Reset */
> >
> > struct serial8250_em_hw_info {
> > unsigned int type;
> > upf_t flags;
> > + void (*serial_out)(struct uart_port *p, int off, int value);
> > };
> >
> > struct serial8250_em_priv {
> > @@ -46,6 +50,7 @@ static void serial8250_em_serial_out(struct uart_port
> *p, int offset, int value)
> > fallthrough;
> > case UART_DLL_EM: /* DLL @ 0x24 (+9) */
> > case UART_DLM_EM: /* DLM @ 0x28 (+9) */
> > + case UART_HCR0: /* HCR0 @ 0x2c */
> > writel(value, p->membase + (offset << 2));
> > }
> > }
> > @@ -55,6 +60,7 @@ static unsigned int serial8250_em_serial_in(struct
> uart_port *p, int offset)
> > switch (offset) {
> > case UART_RX: /* RX @ 0x00 */
> > return readb(p->membase);
> > + case UART_LCR: /* LCR @ 0x10 (+1) */
> > case UART_MCR: /* MCR @ 0x14 (+1) */
> > case UART_LSR: /* LSR @ 0x18 (+1) */
> > case UART_MSR: /* MSR @ 0x1c (+1) */ @@ -64,11 +70,68 @@ static
> > unsigned int serial8250_em_serial_in(struct uart_port *p, int offset)
> > case UART_IIR: /* IIR @ 0x08 */
> > case UART_DLL_EM: /* DLL @ 0x24 (+9) */
> > case UART_DLM_EM: /* DLM @ 0x28 (+9) */
> > + case UART_HCR0: /* HCR0 @ 0x2c */
> > return readl(p->membase + (offset << 2));
> > }
> > return 0;
> > }
> >
> > +static void serial8250_rzv2m_reg_update(struct uart_port *p, int off,
> > +int value) {
> > + unsigned int ier, fcr, lcr, mcr, hcr0;
> > +
> > + ier = serial8250_em_serial_in(p, UART_IER);
> > + lcr = serial8250_em_serial_in(p, UART_LCR);
> > + mcr = serial8250_em_serial_in(p, UART_MCR);
> > + hcr0 = serial8250_em_serial_in(p, UART_HCR0);
> > + /*
> > + * The value of UART_IIR and UART_FCR are 2, but corresponding
> > + * RZ/V2M address offset are different(0x08 and 0x0c). So we need to
> > + * use readl() here.
> > + */
> > + fcr = readl(p->membase + ((UART_FCR + 1) << 2));
>
> I don't get the meaning of that comment. It doesn't seem to match what your
> code does as the code seemingly has nothing to do with IIR (and none of you
> changelogs refer to IIR either)?
The generic macro UART_IIR and UART_FCR in linux/serial_reg.h has a value of 2.
The RZ/V2M register offset don't match with standard ones, we are doing remapping
inside case statements in serial8250_em_serial_in() and serial8250_em_serial_out().
Currently IIR is already present in serial8250_em_serial_in(), so no issue.
But when I tried to add UART_FCR in case, it gives the compilation error.
You cannot have same case values inside switch.
>
> Is the only reason for this that serial8250_em_serial_in() currently lacks
> case UART_FCR: ? Why cannot that just be added there?
Yes, It gives build error.
Cheers,
Biju
>
> --
> i.
>
> > + serial8250_em_serial_out(p, UART_FCR, fcr | UART_FCR_CLEAR_RCVR |
> > + UART_FCR_CLEAR_XMIT);
> > + serial8250_em_serial_out(p, UART_HCR0, hcr0 | UART_HCR0_SW_RESET);
> > + serial8250_em_serial_out(p, UART_HCR0, hcr0 & ~UART_HCR0_SW_RESET);
> > +
> > + switch (off) {
> > + case UART_FCR:
> > + fcr = value;
> > + break;
> > + case UART_LCR:
> > + lcr = value;
> > + break;
> > + case UART_MCR:
> > + mcr = value;
> > + break;
> > + }
> > +
> > + serial8250_em_serial_out(p, UART_IER, ier);
> > + serial8250_em_serial_out(p, UART_FCR, fcr);
> > + serial8250_em_serial_out(p, UART_MCR, mcr);
> > + serial8250_em_serial_out(p, UART_LCR, lcr);
> > + serial8250_em_serial_out(p, UART_HCR0, hcr0); }
> > +
> > +static void serial8250_em_rzv2m_serial_out(struct uart_port *p, int
> > +offset, int value) {
> > + switch (offset) {
> > + case UART_TX:
> > + case UART_SCR:
> > + case UART_IER:
> > + case UART_DLL_EM:
> > + case UART_DLM_EM:
> > + serial8250_em_serial_out(p, offset, value);
> > + break;
> > + case UART_FCR:
> > + case UART_LCR:
> > + case UART_MCR:
> > + serial8250_rzv2m_reg_update(p, offset, value);
> > + }
> > +}
> > +
> > static int serial8250_em_serial_dl_read(struct uart_8250_port *up) {
> > return serial_in(up, UART_DLL_EM) | serial_in(up, UART_DLM_EM) << 8;
> > @@ -120,7 +183,7 @@ static int serial8250_em_probe(struct
> > platform_device *pdev)
> >
> > up.port.iotype = UPIO_MEM32;
> > up.port.serial_in = serial8250_em_serial_in;
> > - up.port.serial_out = serial8250_em_serial_out;
> > + up.port.serial_out = info->serial_out;
> > up.dl_read = serial8250_em_serial_dl_read;
> > up.dl_write = serial8250_em_serial_dl_write;
> >
> > @@ -144,11 +207,13 @@ static int serial8250_em_remove(struct
> > platform_device *pdev) static const struct serial8250_em_hw_info
> emma_mobile_uart_hw_info = {
> > .type = PORT_UNKNOWN,
> > .flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT | UPF_IOREMAP,
> > + .serial_out = serial8250_em_serial_out,
> > };
> >
> > static const struct serial8250_em_hw_info rzv2m_uart_hw_info = {
> > .type = PORT_16750,
> > .flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT | UPF_IOREMAP |
> > UPF_FIXED_TYPE,
> > + .serial_out = serial8250_em_rzv2m_serial_out,
> > };
> >
> > static const struct of_device_id serial8250_em_dt_ids[] = {
> >
