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Message-ID: <CAHQjnOOpaoVAA8RWrYE5yy0eUN=rWLxZ9XEHZR8ajP_AUeOw8Q@mail.gmail.com>
Date: Wed, 7 Dec 2011 17:12:04 +0900
From: KyongHo Cho <pullip.cho@...sung.com>
To: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Ohad Ben-Cohen <ohad@...ery.com>,
linux-samsung-soc@...r.kernel.org,
Russell King <linux@....linux.org.uk>,
linux-kernel@...r.kernel.org,
Younglak Kim <younglak1004.kim@...sung.com>,
iommu@...ts.linux-foundation.org,
Kukjin Kim <kgene.kim@...sung.com>,
Sylwester Nawrocki <s.nawrocki@...sung.com>,
Sanghyun Lee <sanghyun75.lee@...sung.com>,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v7 2/2] iommu/exynos: Add iommu driver for Exynos Platforms
2011/12/6 Marek Szyprowski <m.szyprowski@...sung.com>:
> Hello,
>
> On Tuesday, December 06, 2011 1:21 PM KyongHo Cho wrote:
>
>> On Tue, Dec 6, 2011 at 8:48 PM, Marek Szyprowski
>> <m.szyprowski@...sung.com> wrote:
>> > Hello,
>> >
>> > I'm trying to integrate your SYSMMU driver with my DMA-mapping & IOMMU
>> > API integration patches. I've noticed some issues, please see my comments below.
>> >
>> Thank you!
>>
>> > On Friday, November 18, 2011 10:48 AM KyongHo Cho wrote:
>> >
>> >> +
>> >> +static int exynos_sysmmu_probe(struct platform_device *pdev)
>> >> +{
>> >> + struct resource *res, *ioarea;
>> >> + int ret;
>> >> + int irq;
>> >> + struct device *dev;
>> >> + void *sfr;
>> >> + struct sysmmu_drvdata *data;
>> >> + char *emsg;
>> >> +
>> >> + dev = &pdev->dev;
>> >> +
>> >> + if (dev_get_platdata(dev) == NULL) {
>> >> + pr_debug("%s: No System MMU is assigned for %s.%d.\n", __func__,
>> >> + pdev->name, pdev->id);
>> >> + return -ENODEV;
>> >> + }
>> >> +
>> >> + data = kzalloc(sizeof(*data), GFP_KERNEL);
>> >> + if (!data) {
>> >> + emsg = "Not enough memory";
>> >> + ret = -ENOMEM;
>> >> + goto err_alloc;
>> >> + }
>> >> +
>> >> + data->owner = dev_get_platdata(dev);
>> >> +
>> >> + ret = dev_set_drvdata(dev, data);
>> >> + if (ret) {
>> >> + emsg = "Unable to set driver data.";
>> >> + goto err_init;
>> >> + }
>> >> +
>> >> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> >> + if (!res) {
>> >> + emsg = "Failed probing system MMU: failed to get resource.";
>> >> + goto err_init;
>> >> + }
>> >> +
>> >> + ioarea = request_mem_region(res->start, resource_size(res),
>> >> + dev_name(dev));
>> >> + if (ioarea == NULL) {
>> >> + emsg = "failed to request memory region.";
>> >> + ret = -ENOMEM;
>> >> + goto err_init;
>> >> + }
>> >> +
>> >> + sfr = ioremap(res->start, resource_size(res));
>> >> + if (!sfr) {
>> >> + emsg = "failed to call ioremap().";
>> >> + ret = -ENOENT;
>> >> + goto err_ioremap;
>> >> + }
>> >> +
>> >> + irq = platform_get_irq(pdev, 0);
>> >> + if (irq <= 0) {
>> >> + emsg = "failed to get irq resource.";
>> >> + ret = irq;
>> >> + goto err_irq;
>> >> + }
>> >> +
>> >> + ret = request_irq(irq, exynos_sysmmu_irq, 0, dev_name(dev), data);
>> >> + if (ret) {
>> >> + emsg = "failed to request irq.";
>> >> + goto err_irq;
>> >> + }
>> >> +
>> >> + data->clk = clk_get(dev, "sysmmu");
>> >> + if (IS_ERR(data->clk)) {
>> >> + emsg = "failed to get clock descriptor";
>> >> + ret = PTR_ERR(data->clk);
>> >> + goto err_clk;
>> >> + }
>> >> +
>> >> + data->dev = dev;
>> >> + data->sfrbase = sfr;
>> >> + __set_fault_handler(data, &default_fault_handler);
>> >> + rwlock_init(&data->lock);
>> >
>> > Here is a serious problem: __set_fault_handler takes data->lock which is initialized after
>> calling
>> > this function.
>> >
>>
>> Yeah, you're right. Thank you. I didn't notice it.
>> I will fix it.
>>
>> >> +
>> >> +static unsigned long *alloc_lv2entry(unsigned long *sent, unsigned long iova,
>> >> + short *pgcounter)
>> >> +{
>> >> + if (lv1ent_fault(sent)) {
>> >> + unsigned long *pent;
>> >> +
>> >> + pent = kzalloc(1024, GFP_KERNEL);
>> >
>> > I would use GFP_ATOMIC here. iommu_map() function might be called in atomic context, and
>> > GFP_KERNEL here causes kernel ops/warning.
>>
>> I wanted to avoid to allocate memory from emergency pool.
>> Do you think that it needs to allocate memory with GFP_ATOMIC flag?
>
> Otherwise it will very hard to get it integrated with DMA mapping framework. GFP_ATOMIC
> memory is allocated straight from system free lists, which are refilled on the next
> non-atomic allocation if the watermark level is low enough.
>
> It will be best if iommu_map() can be extended with allocation flags argument, so the
> caller can decide if iommu driver can use GFP_ATOMIC or GFP_KERNEL depending on the context.
>
Understood.
I will change GFP_KERNEL to GFP_ATOMIC in the next patch.
I think it is not good idea to make iommu_map() allocate 2nd level page table
from a specific physical memory pool.
BTW, what about using GFP_KERNEL without __GFP_WAIT?
Then, iommu_map() will fail if there is not enough memory.
Thanks.
KyongHo.
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