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Re: [Qemu-arm] [Qemu-devel] [PATCH v2] char: cadence: check baud rate ge
Re: [Qemu-arm] [Qemu-devel] [PATCH v2] char: cadence: check baud rate generator and divider values
Tue, 25 Oct 2016 15:29:14 -0700
On Tue, Oct 25, 2016 at 11:24 AM, P J P <address@hidden> wrote:
> Hello Alistair,
> +-- On Tue, 25 Oct 2016, Alistair Francis wrote --+
> | > * Device model for Cadence UART
> | > + * ->
> | Can you say what page/section the UART spec is in the Xilinx TRM?
> Chapter 19 UART Controller, page 585, 19.2.3 Baud Rate Generator.
> | I think it might also be worth noting that the datasheet is a Xilinx
> | datasheet that covers the Cadence UART. Others might be using the IP
> | as well and might get confused why you are referring to a Xilinx
> | datasheet.
> Right, I'll add above section details in the comment.
> | > + case R_BRGR: /* Baud rate generator */
> | > + s->r[offset] = 0x028B; /* default reset value */
> | Is this the correct behavior, or should the write just be ignored?
> | pg.587 of the TRM doesn't really make this clear, did you find this
> | somewhere else?
> True, page 587 does not clearly mention if it should be ignored.
> But in Appendix B, Register details for 'Baud_rate_gen_reg0' says
> 0: Disables baud_sample
> 1: Clock divisor bypass (baud_sample = sel_clk)
> 2 - 65535: baud_sample
> | > + case R_BDIV: /* Baud rate divider */
> | > + s->r[offset] = 0x0F;
> Appendix B, Register details for 'Baud_rate_divider_reg0' says
> 0 - 3: ignored
> 4 - 255: Baud rate
> ie. values 0-3 are ignored. But should we avoid writing 's->r[R_BRGR]' &
> 's->r[R_BDIV]' for these values? That would lead to undefined values being
> using in 'uart_parameters_setup()', no?
I think your email crossed with Peter. Have a look at what he said.
That should clarify everything.
> Thank you.
> Prasad J Pandit / Red Hat Product Security Team
> 47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F
Re: [Qemu-arm] [PATCH v2] char: cadence: check baud rate generator and divider values, Peter Maydell, 2016/10/25