netdev - Re: [PATCH 4/6] ethernet: stmmac: fix dma physical address of descriptor when display ring

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Date:   Mon, 11 Jan 2021 09:30:23 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Joakim Zhang <qiangqing.zhang@....com>, peppe.cavallaro@...com,
        alexandre.torgue@...com, joabreu@...opsys.com, davem@...emloft.net,
        kuba@...nel.org
Cc:     netdev@...r.kernel.org, linux-imx@....com
Subject: Re: [PATCH 4/6] ethernet: stmmac: fix dma physical address of
 descriptor when display ring

On 1/11/21 3:35 AM, Joakim Zhang wrote:
> Driver uses dma_alloc_coherent to allocate dma memory for descriptors,
> dma_alloc_coherent will return both the virtual address and physical
> address. AFAIK, virt_to_phys could not convert virtual address to
> physical address, for which memory is allocated by dma_alloc_coherent.
> 
> Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> ---
>  .../ethernet/stmicro/stmmac/dwmac4_descs.c    |  5 +-
>  .../net/ethernet/stmicro/stmmac/enh_desc.c    |  5 +-
>  drivers/net/ethernet/stmicro/stmmac/hwif.h    |  3 +-
>  .../net/ethernet/stmicro/stmmac/norm_desc.c   |  5 +-
>  .../net/ethernet/stmicro/stmmac/stmmac_main.c | 50 ++++++++++++-------
>  5 files changed, 44 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
> index c6540b003b43..8e1ee33ba1e6 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
> @@ -402,7 +402,8 @@ static void dwmac4_rd_set_tx_ic(struct dma_desc *p)
>  	p->des2 |= cpu_to_le32(TDES2_INTERRUPT_ON_COMPLETION);
>  }
>  
> -static void dwmac4_display_ring(void *head, unsigned int size, bool rx)
> +static void dwmac4_display_ring(void *head, unsigned int size, bool rx,
> +				unsigned int dma_rx_phy, unsigned int desc_size)
>  {
>  	struct dma_desc *p = (struct dma_desc *)head;
>  	int i;
> @@ -411,7 +412,7 @@ static void dwmac4_display_ring(void *head, unsigned int size, bool rx)
>  
>  	for (i = 0; i < size; i++) {
>  		pr_info("%03d [0x%x]: 0x%x 0x%x 0x%x 0x%x\n",
> -			i, (unsigned int)virt_to_phys(p),
> +			i, (unsigned int)(dma_rx_phy + i * desc_size),

This code will probably not work correctly on a machine with physical
addresses greater than 32-bit anyway and the address bits would be
truncated then, cannot you use a phy_addr_t or dma_addr_t and use %pa as
far as the printk format goes?
-- 
Florian