linux-kernel - Re: [PATCH RFC 1/1] irqchip/GICv2m: Add support for multiple v2m frames

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Date:	Tue, 13 Oct 2015 07:57:52 -0700
From:	Duc Dang <dhdang@....com>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Jason Cooper <jason@...edaemon.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	patches <patches@....com>
Subject: Re: [PATCH RFC 1/1] irqchip/GICv2m: Add support for multiple v2m frames

On Mon, Oct 12, 2015 at 3:49 AM, Marc Zyngier <marc.zyngier@....com> wrote:
> On 11/10/15 18:13, Duc Dang wrote:
>> On Fri, Oct 9, 2015 at 2:10 AM, Marc Zyngier <marc.zyngier@....com> wrote:
>>> Hi Duc,
>>>
>>> On 08/10/15 08:48, Duc Dang wrote:
>>>> GICv2m driver currently only supports single v2m frame. This
>>>> patch extend this driver to support multiple v2m frames. All of
>>>> the v2m frames will be own by a single MSI domain. Each PCIe node
>>>> can specify msi-parent as the first frame of the v2m frame list
>>>> to be able to use all available v2m frames for MSI interrupts.
>>>>
>>>> This patch should be applied on top of patch
>>>> (irqchip/GICv2m: Add workaround for APM X-Gene GICv2m erratum):
>>>> https://lkml.org/lkml/2015/10/6/922
>>>>
>>>> Signed-off-by: Duc Dang <dhdang@....com>
>>>> ---
>>>>  drivers/irqchip/irq-gic-v2m.c | 221 ++++++++++++++++++++++++++++++------------
>>>>  1 file changed, 159 insertions(+), 62 deletions(-)
>>>>
>>>> diff --git a/drivers/irqchip/irq-gic-v2m.c b/drivers/irqchip/irq-gic-v2m.c
>>>> index 4c17c18..8ecaf9e 100644
>>>> --- a/drivers/irqchip/irq-gic-v2m.c
>>>> +++ b/drivers/irqchip/irq-gic-v2m.c
>>>> @@ -51,13 +51,19 @@
>>>>  #define GICV2M_NEEDS_SPI_OFFSET              0x00000001
>>>>
>>>>  struct v2m_data {
>>>> -     spinlock_t msi_cnt_lock;
>>>>       struct resource res;    /* GICv2m resource */
>>>>       void __iomem *base;     /* GICv2m virt address */
>>>>       u32 spi_start;          /* The SPI number that MSIs start */
>>>>       u32 nr_spis;            /* The number of SPIs for MSIs */
>>>> -     unsigned long *bm;      /* MSI vector bitmap */
>>>>       u32 flags;              /* v2m flags for specific implementation */
>>>> +     struct list_head list;  /* Link to other v2m frames */
>>>> +};
>>>> +
>>>> +struct gicv2m_ctrlr {
>>>> +     spinlock_t v2m_ctrlr_lock;      /* Lock for all v2m frames */
>>>> +     u32 nr_vecs;                    /* Total MSI vectors */
>>>> +     unsigned long *bm;              /* MSI vector bitmap */
>>>> +     struct list_head v2m_frms;      /* List of v2m frames */
>>>>  };
>>>>
>>>>  static void gicv2m_mask_msi_irq(struct irq_data *d)
>>>> @@ -98,11 +104,29 @@ static int gicv2m_set_affinity(struct irq_data *irq_data,
>>>>       return ret;
>>>>  }
>>>>
>>>> +static struct v2m_data *irq_data_to_v2m_frm(struct irq_data *data,
>>>> +                                         struct gicv2m_ctrlr *v2m_ctrlr)
>>>> +{
>>>> +     struct v2m_data *v2m;
>>>> +
>>>> +     list_for_each_entry(v2m, &v2m_ctrlr->v2m_frms, list) {
>>>> +             if ((data->hwirq >= v2m->spi_start) &&
>>>> +                 (data->hwirq < (v2m->spi_start + v2m->nr_spis)))
>>>> +                     return v2m;
>>>> +     }
>>>> +
>>>> +     return NULL;
>>>> +}
>>>> +
>>>>  static void gicv2m_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>>>>  {
>>>> -     struct v2m_data *v2m = irq_data_get_irq_chip_data(data);
>>>> -     phys_addr_t addr = v2m->res.start + V2M_MSI_SETSPI_NS;
>>>> +     struct gicv2m_ctrlr *v2m_ctrlr = irq_data_get_irq_chip_data(data);
>>>> +     struct v2m_data *v2m;
>>>> +     phys_addr_t addr;
>>>>
>>>> +     v2m = irq_data_to_v2m_frm(data, v2m_ctrlr);
>>>> +     WARN_ON(!v2m);
>>>> +     addr = v2m->res.start + V2M_MSI_SETSPI_NS;
>>>
>>> At that particular point, I've stopped reading.
>>>
>>> Pointlessly iterating over the frames when you can store the right one
>>> in irq_data was bad enough, but having a WARN_ON() followed by a panic
>>> is just not acceptable. Either you warn and avoid the crash, or you just
>>> assume that the whole thing is sane and will never be inconsistent.
>>
>> Yes, my bad.
>>>
>>> You are also changing the way this driver works, and not for the best.
>>> I've just written something fairly similar, with the following diffstat:
>>>
>>>  1 file changed, 76 insertions(+), 45 deletions(-)
>>>
>>> The current infrastructure is sound, you just have to make use of it.
>>>
>>> I've pushed the following (untested) patch:
>>>
>>> https://git.kernel.org/cgit/linux/kernel/git/maz/arm-platforms.git/commit/?h=irq/multi-v2m&id=45e35adb60087792626570ff21bb23ab0f67a6ac
>>>
>>> Let me know if that works for you.
>>
>> Yes! I try and your patch definitely works on my X-Gene 2 board.
>
> OK, I'll post that for review, together with your Tested-by tag.

Thanks a lot, Marc.
>
> Thanks,
>
>         M.
> --
> Jazz is not dead. It just smells funny...

Regards,
Duc Dang.
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