[RFC 3/9] MIPS: add virt_to_phys() and phys_to_virt()

[Antony Pavlov]

On Fri, 4 Sep 2015 08:20:48 +0200
Sascha Hauer <s.hauer at pengutronix.de> wrote:

> On Fri, Aug 28, 2015 at 06:46:14PM +0300, Antony Pavlov wrote:
> > On Fri, 28 Aug 2015 08:34:32 +0200
> > Sascha Hauer <s.hauer at pengutronix.de> wrote:
> > 
> > > On Fri, Aug 28, 2015 at 01:24:04AM +0300, Antony Pavlov wrote:
> > > > N.B. phys_to_virt() translates phys address
> > > > to KSEG1 (uncached) address as barebox mips
> > > > has no cache support.
> > > 
> > > What would it take to implement cache support for mips?
> > lack of the cache support is critical problem for current barebox mips support.
> > I'm planning to add cache support in several weeks.
> > This task needs much test efforts for different boards.
> > 
> > Anyway I can't carry out cache adding work at one.
> > But adding virt_to_phys and DMA support will help to add cache support one day anyway.
> 
> Looking at this again the virt_to_phys/phys_to_virt macros are not
> necessary. dma_alloc_coherent() already returns both the virtual address
> and the DMA address. It should be possible to replace DMA_ADDRESS_BROKEN
> in the ehci driver with a real pointer and use it appropriatly in the
> driver.
> 

I have tried to get physical address from dma_alloc_coherent(),
here is a small part of my patch (just for demonstration):

--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -41,6 +41,7 @@ struct ehci_priv {
 	struct ehci_hcor *hcor;
 	struct usb_host host;
 	struct QH *qh_list;
+	dma_addr_t qh_list_dma;
 	struct qTD *td;
 	int portreset;
 	unsigned long flags;
@@ -403,7 +410,7 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
 		goto fail;
 	}
 
-	ehci->qh_list->qh_link = cpu_to_hc32((uint32_t)ehci->qh_list | QH_LINK_TYPE_QH);
+	ehci->qh_list->qh_link = cpu_to_hc32(ehci->qh_list_dma | QH_LINK_TYPE_QH);
 
 	token = hc32_to_cpu(qh->qt_token);
 	if (!(token & 0x80)) {
@@ -1306,7 +1313,7 @@ int ehci_register(struct device_d *dev, struct ehci_data *data)
 	ehci->post_init = data->post_init;
 
 	ehci->qh_list = dma_alloc_coherent(sizeof(struct QH) * NUM_TD,
-					   DMA_ADDRESS_BROKEN);
+					   &ehci->qh_list_dma);
 	ehci->periodic_queue = dma_alloc_coherent(sizeof(struct QH),
 						  DMA_ADDRESS_BROKEN);
 	ehci->td = dma_alloc_coherent(sizeof(struct qTD) * NUM_TD,


However ehci_td_buffer() gets buf pointer outside of ehci driver (e.g. via usb_bulk_msg()),
so it is difficult to avoid virt_to_phys() in ehci_td_buffer(), e.g.:

@@ -195,7 +197,7 @@ static int ehci_td_buffer(struct qTD *td, void *buf, size_t sz)
 
        idx = 0;
        while (idx < 5) {
-               td->qt_buffer[idx] = cpu_to_hc32(addr);
+               td->qt_buffer[idx] = cpu_to_hc32(virt_to_phys(addr));
                next = (addr + 4096) & ~4095;
                delta = next - addr;
                if (delta >= sz)

Have you any idea?

-- 
Best regards,
  Antony Pavlov