Re: [PATCH v8 4/5] usb: ehci: Add new EHCI driver for Broadcom STB SoC's

Alan Stern
2020-05-09T00:47:54Z

On Fri, 8 May 2020, Al Cooper wrote:

A few minor typos in the patch description:

> Add a new EHCI driver for Broadcom STB SoC's. A new EHCI driver
> was created instead of adding support to the existing ehci platform
> driver because of the code required to workaround bugs in the EHCI
-----------------------------------------^

"workaround" is a noun; the verb form is "work around".

> controller. The primary workround is for a bug where the Core
-----------------------------^

Missing "a".

> violates the SOF interval between the first two SOFs transmitted after
> resume. This only happens if the resume occurs near the end of a
> microframe. The fix is to intercept the echi-hcd request to complete
-------------------------------------------^

ehci, not echi.

> RESUME and align it to the start of the next microframe.
>
> Signed-off-by: Al Cooper <alcooperx@gmail.com>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> ---

Basically this new driver is fine. However...

> +static inline void ehci_brcm_wait_for_sof(struct ehci_hcd *ehci, u32 delay)
> +{
> + u32 frame_idx = ehci_readl(ehci, &ehci->regs->frame_index);
> + u32 val;
> + int res;
> +
> + /* Wait for next microframe (every 125 usecs) */
> + res = readl_relaxed_poll_timeout(&ehci->regs->frame_index, val,
> + val != frame_idx, 1, 130);
> + if (res)
> + dev_err(ehci_to_hcd(ehci)->self.controller,
> + "Error waiting for SOF\n");

If this patch is going to be redone anyway, you might as well change
dev_err() to ehci_err() -- that's what it's for. I should have noticed
this earlier, sorry.

> +static int ehci_brcm_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct resource *res_mem;
> + struct brcm_priv *priv;
> + struct usb_hcd *hcd;
> + int irq;
> + int err;
> +
> + err = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));
> + if (err)
> + return err;
> +
> + irq = platform_get_irq(pdev, 0);
> + if (irq <= 0)
> + return irq;

I don't want to get involved in the question of whether or not 0 is a
valid IRQ number. The consensus has gone back and forth over the
years, and it just doesn't seem important.

However, as Sergei points out, if 0 is going to be regarded as an
invalid value then we shouldn't return 0 from the probe function here.

I'll leave the decision on how to handle this matter up to Greg. :-)

Alan Stern