Re: [PATCH 24/25 v7] xen/arm: vpl011: Add a pl011 uart DT node in the guest device tree

[Julien Grall <julien.grall@arm.com>]

On 07/08/17 09:53, Bhupinder Thakur wrote:
> The SBSA UART node format is as specified in
> Documentation/devicetree/bindings/serial/arm_sbsa_uart.txt and given below:
>
> ARM SBSA defined generic UART
> ------------------------------
> This UART uses a subset of the PL011 registers and consequently lives
> in the PL011 driver. It's baudrate and other communication parameters
> cannot be adjusted at runtime, so it lacks a clock specifier here.
>
> Required properties:
> - compatible: must be "arm,sbsa-uart"
> - reg: exactly one register range
> - interrupts: exactly one interrupt specifier
> - current-speed: the (fixed) baud rate set by the firmware
>
> Currently the baud rate of 115200 has been selected as a default value,
> which is one of the valid baud rate settings. Higher baud rate was
> selected since an emulated pl011 can support any valid baud rate without
> any limitation of the hardware.
>
> A check is added to ensure that user specified irq does not conflict with
> the SPI assgined to vpl011. If there is a conflict then it flags an error.
>
> Signed-off-by: Bhupinder Thakur <bhupinder.thakur@linaro.org>
> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> Acked-by: Wei Liu <wei.liu2@citrix.com>
> ---
> CC: Ian Jackson <ian.jackson@eu.citrix.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> CC: Stefano Stabellini <sstabellini@kernel.org>
> CC: Julien Grall <julien.grall@arm.com>
>
> Changes since v6:
> - Added a comment explaining why user specified IRQ should not conflict with vpl011
>   SPI.
> - Checking the vuart type explicitly against vpl011 enum type.
> - Removed uart-compat string and using "arm,sbsa-uart" string directly.
> - I have retained the reviewed-by/acked-by tags as these are minor changes.
>
>  tools/libxl/libxl_arm.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
>
> diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c
> index a33d3c9..6629852 100644
> --- a/tools/libxl/libxl_arm.c
> +++ b/tools/libxl/libxl_arm.c
> @@ -43,11 +43,29 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
>  {
>      uint32_t nr_spis = 0;
>      unsigned int i;
> +    uint32_t vuart_irq = 0;
> +
> +    /*
> +     * If pl011 vuart is enabled then increment the nr_spis to allow allocation
> +     * of SPI VIRQ for pl011.
> +     */
> +    if (d_config->b_info.arch_arm.vuart == LIBXL_VUART_TYPE_SBSA_UART) {
> +        nr_spis += (GUEST_VPL011_SPI - 32) + 1;
> +        vuart_irq = GUEST_VPL011_SPI;
> +    }
>
>      for (i = 0; i < d_config->b_info.num_irqs; i++) {
>          uint32_t irq = d_config->b_info.irqs[i];
>          uint32_t spi;
>
> +        /*
> +         * The user specified irq should not conflict with the vpl011 irq.
> +         */

I am sorry but in the changelog you wrote: "Add a comment explaining why 
user specified IRQ should not conflict with vpl011 SPI". But you still 
don't explain why... And I still don't see the TODO requested on v6.

> +        if (irq == vuart_irq) {

Hmmm if vUART is not enabled you would compare to 0. And I don't think 
we should make this assumption in the code. This would also give a 
random error to the user.

It would be better if you introduce a local boolean vuart_enabled to 
know whether you need to check the conflict.

> +            LOG(ERROR, "Physical IRQ %u conflicting with pl011 SPI\n", irq);
> +            return ERROR_FAIL;
> +        }
> +
>          if (irq < 32)
>              continue;
>
> @@ -590,6 +608,38 @@ static int make_hypervisor_node(libxl__gc *gc, void *fdt,
>      return 0;
>  }
>
> +static int make_vpl011_uart_node(libxl__gc *gc, void *fdt,
> +                                 const struct arch_info *ainfo,
> +                                 struct xc_dom_image *dom)
> +{
> +    int res;
> +    gic_interrupt intr;
> +
> +    res = fdt_begin_node(fdt, "sbsa-pl011");
> +    if (res) return res;
> +
> +    res = fdt_property_compat(gc, fdt, 1, "arm,sbsa-uart");
> +    if (res) return res;
> +
> +    res = fdt_property_regs(gc, fdt, ROOT_ADDRESS_CELLS, ROOT_SIZE_CELLS,
> +                            1,
> +                            GUEST_PL011_BASE, GUEST_PL011_SIZE);
> +    if (res) return res;
> +
> +    set_interrupt(intr, GUEST_VPL011_SPI, 0xf, DT_IRQ_TYPE_LEVEL_HIGH);
> +
> +    res = fdt_property_interrupts(gc, fdt, &intr, 1);
> +    if (res) return res;
> +
> +    /* Use a default baud rate of 115200. */
> +    fdt_property_u32(fdt, "current-speed", 115200);
> +
> +    res = fdt_end_node(fdt);
> +    if (res) return res;
> +
> +    return 0;
> +}
> +
>  static const struct arch_info *get_arch_info(libxl__gc *gc,
>                                               const struct xc_dom_image *dom)
>  {
> @@ -889,6 +939,9 @@ next_resize:
>          FDT( make_timer_node(gc, fdt, ainfo, xc_config->clock_frequency) );
>          FDT( make_hypervisor_node(gc, fdt, vers) );
>
> +        if (info->arch_arm.vuart == LIBXL_VUART_TYPE_SBSA_UART)
> +            FDT( make_vpl011_uart_node(gc, fdt, ainfo, dom) );
> +
>          if (pfdt)
>              FDT( copy_partial_fdt(gc, fdt, pfdt) );
>
>

Cheers,

-- 
Julien Grall

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