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Date: Fri, 18 Nov 2022 21:30:54 +0100
From: "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To: netdev@...r.kernel.org,
Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>
Cc: Ira Weiny <ira.weiny@...el.com>
Subject: Re: [PATCH net-next 3/5] cassini: Remove unnecessary use of kmap_atomic()
On venerdì 18 novembre 2022 18:55:36 CET Anirudh Venkataramanan wrote:
> On 11/18/2022 12:35 AM, Fabio M. De Francesco wrote:
> > On giovedì 17 novembre 2022 23:25:55 CET Anirudh Venkataramanan wrote:
> >> Pages for Rx buffers are allocated in cas_page_alloc() using either
> >> GFP_ATOMIC or GFP_KERNEL. Memory allocated with GFP_KERNEL/GFP_ATOMIC
> >> can't come from highmem and so there's no need to kmap() them. Just use
> >> page_address() instead.
> >>
> >> I don't have hardware, so this change has only been compile tested.
> >>
> >> Cc: Ira Weiny <ira.weiny@...el.com>
> >> Cc: Fabio M. De Francesco <fmdefrancesco@...il.com>
> >> Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>
> >> ---
> >>
> >> drivers/net/ethernet/sun/cassini.c | 34 ++++++++++--------------------
> >> 1 file changed, 11 insertions(+), 23 deletions(-)
> >>
> >> diff --git a/drivers/net/ethernet/sun/cassini.c
> >> b/drivers/net/ethernet/sun/cassini.c index 0aca193..2f66cfc 100644
> >> --- a/drivers/net/ethernet/sun/cassini.c
> >> +++ b/drivers/net/ethernet/sun/cassini.c
> >> @@ -1915,7 +1915,7 @@ static int cas_rx_process_pkt(struct cas *cp,
struct
> >> cas_rx_comp *rxc, int off, swivel = RX_SWIVEL_OFF_VAL;
> >>
> >> struct cas_page *page;
> >> struct sk_buff *skb;
> >>
> >> - void *addr, *crcaddr;
> >> + void *crcaddr;
> >>
> >> __sum16 csum;
> >> char *p;
> >>
> >> @@ -1936,7 +1936,7 @@ static int cas_rx_process_pkt(struct cas *cp,
struct
> >> cas_rx_comp *rxc, skb_reserve(skb, swivel);
> >>
> >> p = skb->data;
> >>
> >> - addr = crcaddr = NULL;
> >> + crcaddr = NULL;
> >>
> >> if (hlen) { /* always copy header pages */
> >>
> >> i = CAS_VAL(RX_COMP2_HDR_INDEX, words[1]);
> >> page = cp->rx_pages[CAS_VAL(RX_INDEX_RING, i)]
> >
> > [CAS_VAL(RX_INDEX_NUM, i)];
> >
> >> @@ -1948,12 +1948,10 @@ static int cas_rx_process_pkt(struct cas *cp,
> >> struct
> >> cas_rx_comp *rxc, i += cp->crc_size;
> >>
> >> dma_sync_single_for_cpu(&cp->pdev->dev, page->dma_addr +
> >
> > off,
> >
> >> i, DMA_FROM_DEVICE);
> >>
> >> - addr = cas_page_map(page->buffer);
> >> - memcpy(p, addr + off, i);
> >> + memcpy(p, page_address(page->buffer) + off, i);
> >>
> >> dma_sync_single_for_device(&cp->pdev->dev,
> >>
> >> page->dma_addr + off, i,
> >> DMA_FROM_DEVICE);
> >>
> >> - cas_page_unmap(addr);
> >>
> >> RX_USED_ADD(page, 0x100);
> >> p += hlen;
> >> swivel = 0;
> >>
> >> @@ -1984,12 +1982,11 @@ static int cas_rx_process_pkt(struct cas *cp,
> >> struct
> >> cas_rx_comp *rxc, /* make sure we always copy a header */
> >>
> >> swivel = 0;
> >> if (p == (char *) skb->data) { /* not split */
> >>
> >> - addr = cas_page_map(page->buffer);
> >> - memcpy(p, addr + off, RX_COPY_MIN);
> >> + memcpy(p, page_address(page->buffer) + off,
> >> + RX_COPY_MIN);
> >>
> >> dma_sync_single_for_device(&cp->pdev->dev,
> >>
> >> page->dma_addr
> >
> > + off, i,
> >
> > DMA_FROM_DEVICE);
> >
> >> - cas_page_unmap(addr);
> >>
> >> off += RX_COPY_MIN;
> >> swivel = RX_COPY_MIN;
> >> RX_USED_ADD(page, cp->mtu_stride);
> >>
> >> @@ -2036,10 +2033,8 @@ static int cas_rx_process_pkt(struct cas *cp,
struct
> >> cas_rx_comp *rxc, RX_USED_ADD(page, hlen + cp->crc_size);
> >>
> >> }
> >>
> >> - if (cp->crc_size) {
> >> - addr = cas_page_map(page->buffer);
> >> - crcaddr = addr + off + hlen;
> >> - }
> >> + if (cp->crc_size)
> >> + crcaddr = page_address(page->buffer) + off +
> >
> > hlen;
> >
> >> } else {
> >>
> >> /* copying packet */
> >>
> >> @@ -2061,12 +2056,10 @@ static int cas_rx_process_pkt(struct cas *cp,
> >> struct
> >> cas_rx_comp *rxc, i += cp->crc_size;
> >>
> >> dma_sync_single_for_cpu(&cp->pdev->dev, page->dma_addr +
> >
> > off,
> >
> >> i, DMA_FROM_DEVICE);
> >>
> >> - addr = cas_page_map(page->buffer);
> >> - memcpy(p, addr + off, i);
> >> + memcpy(p, page_address(page->buffer) + off, i);
> >>
> >> dma_sync_single_for_device(&cp->pdev->dev,
> >>
> >> page->dma_addr + off, i,
> >> DMA_FROM_DEVICE);
> >>
> >> - cas_page_unmap(addr);
> >>
> >> if (p == (char *) skb->data) /* not split */
> >>
> >> RX_USED_ADD(page, cp->mtu_stride);
> >>
> >> else
> >>
> >> @@ -2081,20 +2074,17 @@ static int cas_rx_process_pkt(struct cas *cp,
> >> struct
> >> cas_rx_comp *rxc, page->dma_addr,
> >>
> >> dlen + cp-
> >>
> >> crc_size,
> >>
> >> DMA_FROM_DEVICE);
> >>
> >> - addr = cas_page_map(page->buffer);
> >> - memcpy(p, addr, dlen + cp->crc_size);
> >> + memcpy(p, page_address(page->buffer), dlen + cp-
> >> crc_size);
> >>
> >> dma_sync_single_for_device(&cp->pdev->dev,
> >>
> >> page->dma_addr,
> >> dlen + cp-
> >>
> >> crc_size,
> >
> > DMA_FROM_DEVICE);
> >
> >> - cas_page_unmap(addr);
> >>
> >> RX_USED_ADD(page, dlen + cp->crc_size);
> >>
> >> }
> >>
> >> end_copy_pkt:
> >> - if (cp->crc_size) {
> >> - addr = NULL;
> >> + if (cp->crc_size)
> >>
> >> crcaddr = skb->data + alloclen;
> >>
> >> - }
> >> +
> >
> > This is a different logical change. Some maintainers I met would have
asked
> > for a separate patch, but I'm OK with it being here.
>
> cas_page_map()/cap_page_unmap() were using addr. Once these went away
> addr became unnecessary. It would be weird to leave the declaration,
> init and reinit for a variable that's not of any use, and so it was
> removed as well. It's cleaner this way.
>
> Ani
Oh, sorry. You are right here. I didn't notice this connection. I probably
took too little time to read your code carefully and interpreted those two
lines another way :-(
Thanks,
Fabio
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