[PATCH v7 2/2] iommu/exynos: Add iommu driver for Exynos Platforms

Hello,

On Tuesday, December 06, 2011 1:21 PM KyongHo Cho wrote:

On Tue, Dec 6, 2011 at 8:48 PM, Marek Szyprowski
[off-list ref] wrote:

quoted

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!

quoted

On Friday, November 18, 2011 10:48 AM KyongHo Cho wrote:

quoted

+
+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

quoted

this function.

Yeah, you're right. Thank you. I didn't notice it.
I will fix it.

quoted

quoted

+
+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. 

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center