Re: [RFC v3 5/7] dmaengine: Add Synopsys eDMA IP PCIe glue-logic

[Gustavo Pimentel <gustavo.pimentel@synopsys.com>]

On 11/01/2019 19:47, Andy Shevchenko wrote:
> On Fri, Jan 11, 2019 at 07:33:41PM +0100, Gustavo Pimentel wrote:
>> Synopsys eDMA IP is normally distributed along with Synopsys PCIe
>> EndPoint IP (depends of the use and licensing agreement).
>>
>> This IP requires some basic configurations, such as:
>>  - eDMA registers BAR
>>  - eDMA registers offset
>>  - eDMA registers size
>>  - eDMA linked list memory BAR
>>  - eDMA linked list memory offset
>>  - eDMA linked list memory sze
>>  - eDMA data memory BAR
>>  - eDMA data memory offset
>>  - eDMA data memory size
>>  - eDMA version
>>  - eDMA mode
>>  - IRQs available for eDMA
>>
>> As a working example, PCIe glue-logic will attach to a Synopsys PCIe
>> EndPoint IP prototype kit (Vendor ID = 0x16c3, Device ID = 0xedda),
>> which has built-in an eDMA IP with this default configuration:
>>  - eDMA registers BAR = 0
>>  - eDMA registers offset = 0x00001000 (4 Kbytes)
>>  - eDMA registers size = 0x00002000 (8 Kbytes)
>>  - eDMA linked list memory BAR = 2
>>  - eDMA linked list memory offset = 0x00000000 (0 Kbytes)
>>  - eDMA linked list memory size = 0x00800000 (8 Mbytes)
>>  - eDMA data memory BAR = 2
>>  - eDMA data memory offset = 0x00800000 (8 Mbytes)
>>  - eDMA data memory size = 0x03800000 (56 Mbytes)
>>  - eDMA version = 0
>>  - eDMA mode = EDMA_MODE_UNROLL
>>  - IRQs = 1
>>
>> This driver can be compile as built-in or external module in kernel.
>>
>> To enable this driver just select DW_EDMA_PCIE option in kernel
>> configuration, however it requires and selects automatically DW_EDMA
>> option too.
>>
> 
>> Changes:
>> RFC v1->RFC v2:
> 
> Changes go after '--- ' line.

At the last Linux Plumbers Conference there were some subsystem maintainers who
asked that the track changes be included in the description as a way to not lose
the previous work done. That why I put it before the '---' line, but it's
indifferent to me, I can put it after the '---' line.

> 
>>  - Replace comments // (C99 style) by /**/
>>  - Merge two pcim_iomap_regions() calls into just one call
>>  - Remove pci_try_set_mwi() call
>>  - Replace some dev_info() by dev_dbg() to reduce *noise*
>>  - Remove pci_name(pdev) call after being call dw_edma_remove()
>>  - Remove all power management support
>>  - Fix the headers of the .c and .h files according to the most recent
>>    convention
>>  - Fix errors and checks pointed out by checkpatch with --strict option
>>  - Replace patch small description tag from dma by dmaengine
>> RFC v2->RFC v3:
>>  - Fix printk variable of phys_addr_t type
>>  - Fix missing variable initialization (chan->configured)
>>  - Change linked list size to 512 Kbytes
>>  - Add data memory information
>>  - Add register size information
>>  - Add comments or improve existing ones
>>  - Add possibility to work with multiple IRQs feature
>>  - Replace MSI and MSI-X enable condition by pci_dev_msi_enabled()
>>  - Replace code to acquire MSI(-X) address and data by
>>    get_cached_msi_msg()
> 
>> +enum dw_edma_pcie_bar {
>> +	BAR_0,
>> +	BAR_1,
>> +	BAR_2,
>> +	BAR_3,
>> +	BAR_4,
>> +	BAR_5
>> +};
> 
> pci-epf.h has this.
> Why duplicate?

I can use that header sure. Thanks.

> 
> 
> What else is being duplicated from PCI core?
> 
>> +static bool disable_msix;
>> +module_param(disable_msix, bool, 0644);
>> +MODULE_PARM_DESC(disable_msix, "Disable MSI-X interrupts");
> 
> Why?!
> We are no allow new module parameters without very strong arguments.

Since this is a reference driver and might be used to test customized HW
solutions, I added this parameter to allow the possibility to test the solution
forcing the MSI feature binding. This is required specially if who will test
this solution has a Root Complex with both features available (MSI and MSI-X),
because the Kernel will give always preference to MSI-X binding (assuming that
the EP has also both features available).

> 
>> +
>> +static int dw_edma_pcie_probe(struct pci_dev *pdev,
>> +			      const struct pci_device_id *pid)
>> +{
>> +	const struct dw_edma_pcie_data *pdata = (void *)pid->driver_data;
>> +	struct device *dev = &pdev->dev;
>> +	struct dw_edma_chip *chip;
>> +	struct dw_edma *dw;
>> +	unsigned int irq_flags = PCI_IRQ_MSI;
>> +	int err, nr_irqs, i;
>> +
> 
>> +	if (!pdata) {
>> +		dev_err(dev, "%s missing data structure\n", pci_name(pdev));
>> +		return -EFAULT;
>> +	}
> 
> Useless check.

Why? It's just a precaution, isn't it a good practice always to think of the
worst case?

> 
>> +
>> +	/* Enable PCI device */
>> +	err = pcim_enable_device(pdev);
>> +	if (err) {
>> +		dev_err(dev, "%s enabling device failed\n", pci_name(pdev));
>> +		return err;
>> +	}
>> +
>> +	/* Mapping PCI BAR regions */
>> +	err = pcim_iomap_regions(pdev, BIT(pdata->rg_bar) |
>> +				       BIT(pdata->ll_bar) |
>> +				       BIT(pdata->dt_bar),
>> +				 pci_name(pdev));
>> +	if (err) {
> 
>> +		dev_err(dev, "%s eDMA BAR I/O remapping failed\n",
>> +			pci_name(pdev));
> 
> Isn't it pci_err() ?
> Same comment for the rest similar cases above and below.

Ok, I'll replace all dev_* function in this file.
Thanks.

> 
>> +		return err;
>> +	}
>> +
>> +	pci_set_master(pdev);
>> +
>> +	nr_irqs = pci_alloc_irq_vectors(pdev, 1, pdata->irqs_cnt, irq_flags);
>> +	if (nr_irqs < 1) {
>> +		dev_err(dev, "%s failed to alloc IRQ vector (Number of IRQs=%u)\n",
>> +			pci_name(pdev), nr_irqs);
>> +		return -EPERM;
>> +	}
>> +
>> +	/* Data structure initialization */
>> +	chip->dw = dw;
>> +	chip->dev = dev;
>> +	chip->id = pdev->devfn;
>> +	chip->irq = pdev->irq;
>> +
> 
>> +	if (!pcim_iomap_table(pdev))
>> +		return -EACCES;
> 
> Never happen condition. Thus useless.

pcim_iomap_table() can return NULL in case of allocation failure. Besides that,
isn't it a good practice always to think of the worst case?

> 
>> +	dev_info(dev, "DesignWare eDMA PCIe driver loaded completely\n");
> 
> Useless.

It's helpful for bring up, I can pass it to dbg.

> 
>> +}
>> +
>> +static void dw_edma_pcie_remove(struct pci_dev *pdev)
>> +{
>> +	struct dw_edma_chip *chip = pci_get_drvdata(pdev);
>> +	struct device *dev = &pdev->dev;
>> +	int err;
>> +
>> +	/* Stopping eDMA driver */
>> +	err = dw_edma_remove(chip);
>> +	if (err)
>> +		dev_warn(dev, "can't remove device properly: %d\n", err);
>> +
>> +	/* Freeing IRQs */
>> +	pci_free_irq_vectors(pdev);
>> +
>> +	dev_info(dev, "DesignWare eDMA PCIe driver unloaded completely\n");
> 
> Ditto.

It's helpful for bring up, I can pass it to dbg.

> 
>> +}
> 
>> +MODULE_DEVICE_TABLE(pci, dw_edma_pcie_id_table);
>> +
>> +static struct pci_driver dw_edma_pcie_driver = {
>> +	.name		= "dw-edma-pcie",
>> +	.id_table	= dw_edma_pcie_id_table,
>> +	.probe		= dw_edma_pcie_probe,
>> +	.remove		= dw_edma_pcie_remove,
> 
> Power management?

I've removed the power management for now, since with my current setup I don't
have the necessary conditions to test it. I prefer not submitting that code for now.

> 
>> +};
> 

Thanks for the inputs Andy! They have been pretty good!

Regards,
Gustavo