Subject: [PATCH RFC 1/1] irqchip/GICv2m: Add support for multiple v2m frames

From: [email-masked] (Marc Zyngier)
Date: Mon, 12 Oct 2015 11:49:02 +0100

On 11/10/15 18:13, Duc Dang wrote:
> On Fri, Oct 9, 2015 at 2:10 AM, Marc Zyngier <[email-masked]> 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 <[email-masked]>
>>> ---
>>>  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,

	M.
-- 
Jazz is not dead. It just smells funny...