[PATCH RFC 6/6] arm64: wait for transmit completion before next character transmission
Minfei Huang
mhuang at redhat.com
Thu Apr 16 22:36:21 PDT 2015
On 04/16/15 at 10:17pm, Pratyush Anand wrote:
> Previous transmission must be completed before next character to be
> transmitted, otherwise TX buffer may saturate and we will not see all
> the characters on screen.
>
> Signed-off-by: Pratyush Anand <panand at redhat.com>
> ---
> kexec/arch/arm64/include/arch/options.h | 10 +++++++++-
> kexec/arch/arm64/kexec-arm64.c | 17 +++++++++++++++++
> purgatory/arch/arm64/entry.S | 10 ++++++++++
> purgatory/arch/arm64/purgatory-arm64.c | 22 +++++++++++++++++++++-
> 4 files changed, 57 insertions(+), 2 deletions(-)
>
> diff --git a/kexec/arch/arm64/include/arch/options.h b/kexec/arch/arm64/include/arch/options.h
> index af14102220ea..a1f6f2cb00be 100644
> --- a/kexec/arch/arm64/include/arch/options.h
> +++ b/kexec/arch/arm64/include/arch/options.h
> @@ -8,7 +8,9 @@
> #define OPT_PAGE_OFFSET ((OPT_MAX)+4)
> #define OPT_PORT ((OPT_MAX)+5)
> #define OPT_REUSE_CMDLINE ((OPT_MAX+6))
> -#define OPT_ARCH_MAX ((OPT_MAX)+7)
> +#define OPT_PORT_LSR ((OPT_MAX)+7)
> +#define OPT_PORT_LSR_VAL ((OPT_MAX)+8)
> +#define OPT_ARCH_MAX ((OPT_MAX)+9)
>
> #define KEXEC_ARCH_OPTIONS \
> KEXEC_OPTIONS \
> @@ -19,6 +21,8 @@
> { "lite", 0, NULL, OPT_LITE }, \
> { "page-offset", 1, NULL, OPT_PAGE_OFFSET }, \
> { "port", 1, NULL, OPT_PORT }, \
> + { "port-lsr", 1, NULL, OPT_PORT_LSR }, \
> + { "port-lsr-val", 1, NULL, OPT_PORT_LSR_VAL }, \
> { "ramdisk", 1, NULL, OPT_INITRD }, \
> { "reuse-cmdline", 0, NULL, OPT_REUSE_CMDLINE }, \
>
> @@ -34,6 +38,8 @@ static const char arm64_opts_usage[] __attribute__ ((unused)) =
> " --lite Fast reboot, no memory integrity checks.\n"
> " --page-offset Kernel page-offset for binary image load.\n"
> " --port=ADDRESS Purgatory output to port ADDRESS.\n"
> +" --port-lsr=ADDRESS Purgatory output port line status ADDRESS.\n"
> +" --port-lsr-val=VALUE Purgatory output port Line status expected SET value when TX empty.\n"
> " --ramdisk=FILE Use FILE as the kernel initial ramdisk.\n"
> " --reuse-cmdline Use command line arg of primary kernel.\n";
>
> @@ -43,6 +49,8 @@ struct arm64_opts {
> const char *initrd;
> uint64_t page_offset;
> uint64_t port;
> + uint64_t port_lsr;
> + uint32_t port_lsr_val;
> int lite;
> };
>
> diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
> index 190037c75186..5c7445b86305 100644
> --- a/kexec/arch/arm64/kexec-arm64.c
> +++ b/kexec/arch/arm64/kexec-arm64.c
> @@ -99,6 +99,12 @@ int arch_process_options(int argc, char **argv)
> case OPT_PORT:
> arm64_opts.port = strtoull(optarg, NULL, 0);
> break;
> + case OPT_PORT_LSR:
> + arm64_opts.port_lsr = strtoull(optarg, NULL, 0);
> + break;
> + case OPT_PORT_LSR_VAL:
> + arm64_opts.port_lsr_val = strtoull(optarg, NULL, 0);
> + break;
> case OPT_PAGE_OFFSET:
> arm64_opts.page_offset = strtoull(optarg, NULL, 0);
> break;
> @@ -594,6 +600,8 @@ int arm64_load_other_segments(struct kexec_info *info,
> unsigned long dtb_base;
> char *initrd_buf = NULL;
> uint64_t purgatory_sink;
> + uint64_t purgatory_sink_lsr;
> + uint32_t purgatory_sink_lsr_val;
> unsigned long purgatory_base;
> struct dtb dtb_1 = {.name = "dtb_1"};
> struct dtb dtb_2 = {.name = "dtb_2"};
> @@ -615,6 +623,9 @@ int arm64_load_other_segments(struct kexec_info *info,
> dbgprintf("%s:%d: purgatory sink: 0x%" PRIx64 "\n", __func__, __LINE__,
> purgatory_sink);
>
> + purgatory_sink_lsr = arm64_opts.port_lsr;
> + purgatory_sink_lsr_val = arm64_opts.port_lsr_val;
> +
> if (arm64_opts.dtb) {
> dtb_2.buf = slurp_file(arm64_opts.dtb, &dtb_2.size);
> assert(dtb_2.buf);
> @@ -732,6 +743,12 @@ int arm64_load_other_segments(struct kexec_info *info,
> elf_rel_set_symbol(&info->rhdr, "arm64_sink", &purgatory_sink,
> sizeof(purgatory_sink));
>
> + elf_rel_set_symbol(&info->rhdr, "arm64_sink_lsr",
> + &purgatory_sink_lsr, sizeof(purgatory_sink_lsr));
> +
> + elf_rel_set_symbol(&info->rhdr, "arm64_sink_lsr_val",
> + &purgatory_sink_lsr_val, sizeof(purgatory_sink_lsr_val));
> +
> elf_rel_set_symbol(&info->rhdr, "arm64_kernel_entry",
> &kernel_entry, sizeof(kernel_entry));
>
> diff --git a/purgatory/arch/arm64/entry.S b/purgatory/arch/arm64/entry.S
> index 140e91d87ab1..fdb2fca774e7 100644
> --- a/purgatory/arch/arm64/entry.S
> +++ b/purgatory/arch/arm64/entry.S
> @@ -43,6 +43,11 @@ arm64_sink:
> .quad 0
> size arm64_sink
>
> +.globl arm64_sink_lsr
> +arm64_sink_lsr:
> + .quad 0
> +size arm64_sink_lsr
> +
> .globl arm64_kernel_entry
> arm64_kernel_entry:
> .quad 0
> @@ -52,3 +57,8 @@ size arm64_kernel_entry
> arm64_dtb_addr:
> .quad 0
> size arm64_dtb_addr
> +
> +.globl arm64_sink_lsr_val
> +arm64_sink_lsr_val:
> + .word 0
Since arm64_sink_lsr_val is declared as uint32_t, it is better to keep
the same format here.
Thanks
Minfei
> +size arm64_sink_lsr_val
> diff --git a/purgatory/arch/arm64/purgatory-arm64.c b/purgatory/arch/arm64/purgatory-arm64.c
> index 25960c30bd05..1b88bb799f54 100644
> --- a/purgatory/arch/arm64/purgatory-arm64.c
> +++ b/purgatory/arch/arm64/purgatory-arm64.c
> @@ -8,18 +8,38 @@
> /* Symbols set by kexec. */
>
> extern uint32_t *arm64_sink;
> +extern uint32_t *arm64_sink_lsr;
> +extern uint32_t arm64_sink_lsr_val;
> extern void (*arm64_kernel_entry)(uint64_t);
> extern uint64_t arm64_dtb_addr;
>
> +static void wait_for_xmit_complete(void)
> +{
> + volatile uint32_t status;
> + volatile uint32_t *status_reg = (volatile uint32_t *)arm64_sink_lsr;
> +
> + if (!arm64_sink_lsr)
> + return;
> +
> + while (1) {
> + status = *status_reg;
> + if ((status & arm64_sink_lsr_val) == arm64_sink_lsr_val)
> + break;
> + }
> +}
> +
> void putchar(int ch)
> {
> if (!arm64_sink)
> return;
>
> + wait_for_xmit_complete();
> *arm64_sink = ch;
>
> - if (ch == '\n')
> + if (ch == '\n') {
> + wait_for_xmit_complete();
> *arm64_sink = '\r';
> + }
> }
>
> void setup_arch(void)
> --
> 2.1.0
>
>
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