[PATCH net-next 1/2] net: stmmac: fix unsafe MTL DMA macro

[PATCH net-next 1/2] net: stmmac: fix unsafe MTL DMA macro

[Junxiao Chang]

Macro like "#define abc(x) (x, x)" is unsafe which might introduce
side effects. Each MTL RxQ DMA channel mask is 4 bits, so using
(0xf << chan) instead of GENMASK(x + 3, x) to avoid unsafe macro.

Fixes: d43042f4da3e ("net: stmmac: mapping mtl rx to dma channel")
Signed-off-by: Junxiao Chang <junxiao.chang@intel.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac4.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
index 71dad409f78b0..3c1490408a1c3 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
@@ -333,7 +333,7 @@ enum power_event {
 #define MTL_RXQ_DMA_MAP1		0x00000c34 /* queue 4 to 7 */
 #define MTL_RXQ_DMA_Q04MDMACH_MASK	GENMASK(3, 0)
 #define MTL_RXQ_DMA_Q04MDMACH(x)	((x) << 0)
-#define MTL_RXQ_DMA_QXMDMACH_MASK(x)	GENMASK(11 + (8 * ((x) - 1)), 8 * (x))
+#define MTL_RXQ_DMA_QXMDMACH_MASK(x)	(0xf << 8 * (x))
 #define MTL_RXQ_DMA_QXMDMACH(chan, q)	((chan) << (8 * (q)))
 
 #define MTL_CHAN_BASE_ADDR		0x00000d00
-- 
2.25.1

[PATCH net-next 2/2] net: stmmac: remove duplicate dma queue channel macros

[Junxiao Chang]

It doesn't need extra macros for queue 0 & 4. Same macro could
be used for all 8 queues.

Signed-off-by: Junxiao Chang <junxiao.chang@intel.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac4.h      |  2 --
 drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c | 11 ++++-------
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
index 3c1490408a1c3..ccd49346d3b30 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
@@ -331,8 +331,6 @@ enum power_event {
 
 #define MTL_RXQ_DMA_MAP0		0x00000c30 /* queue 0 to 3 */
 #define MTL_RXQ_DMA_MAP1		0x00000c34 /* queue 4 to 7 */
-#define MTL_RXQ_DMA_Q04MDMACH_MASK	GENMASK(3, 0)
-#define MTL_RXQ_DMA_Q04MDMACH(x)	((x) << 0)
 #define MTL_RXQ_DMA_QXMDMACH_MASK(x)	(0xf << 8 * (x))
 #define MTL_RXQ_DMA_QXMDMACH(chan, q)	((chan) << (8 * (q)))
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
index c25bfecb4a2df..64b916728bdd4 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
@@ -219,15 +219,12 @@ static void dwmac4_map_mtl_dma(struct mac_device_info *hw, u32 queue, u32 chan)
 	else
 		value = readl(ioaddr + MTL_RXQ_DMA_MAP1);
 
-	if (queue == 0 || queue == 4) {
-		value &= ~MTL_RXQ_DMA_Q04MDMACH_MASK;
-		value |= MTL_RXQ_DMA_Q04MDMACH(chan);
-	} else if (queue > 4) {
-		value &= ~MTL_RXQ_DMA_QXMDMACH_MASK(queue - 4);
-		value |= MTL_RXQ_DMA_QXMDMACH(chan, queue - 4);
-	} else {
+	if (queue < 4) {
 		value &= ~MTL_RXQ_DMA_QXMDMACH_MASK(queue);
 		value |= MTL_RXQ_DMA_QXMDMACH(chan, queue);
+	} else {
+		value &= ~MTL_RXQ_DMA_QXMDMACH_MASK(queue - 4);
+		value |= MTL_RXQ_DMA_QXMDMACH(chan, queue - 4);
 	}
 
 	if (queue < 4)
-- 
2.25.1

Re: [PATCH net-next 1/2] net: stmmac: fix unsafe MTL DMA macro

[Jakub Kicinski]

On Fri, 21 Oct 2022 19:47:10 +0800 Junxiao Chang wrote:
> Macro like "#define abc(x) (x, x)" is unsafe which might introduce
> side effects. Each MTL RxQ DMA channel mask is 4 bits, so using
> (0xf << chan) instead of GENMASK(x + 3, x) to avoid unsafe macro.
> 
> Fixes: d43042f4da3e ("net: stmmac: mapping mtl rx to dma channel")

You need to point out an existing usage where this is causing problems,
otherwise this is not a fix.

And squash the two patches together, it's going to be easier to review.

RE: [PATCH net-next 1/2] net: stmmac: fix unsafe MTL DMA macro

[Chang, Junxiao]

Thank you for reviewing it. There is no real issue if this macro only be used in stmmac driver and parameter is not function or "i++".

I will squash these two patches.

Regards,
Junxiao

-----Original Message-----
From: Jakub Kicinski <kuba@kernel.org> 
Sent: Tuesday, October 25, 2022 12:00 PM
To: Chang, Junxiao <junxiao.chang@intel.com>
Cc: peppe.cavallaro@st.com; alexandre.torgue@foss.st.com; joabreu@synopsys.com; davem@davemloft.net; edumazet@google.com; pabeni@redhat.com; mcoquelin.stm32@gmail.com; Joao.Pinto@synopsys.com; netdev@vger.kernel.org; linux-stm32@st-md-mailman.stormreply.com; linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next 1/2] net: stmmac: fix unsafe MTL DMA macro

On Fri, 21 Oct 2022 19:47:10 +0800 Junxiao Chang wrote:
> Macro like "#define abc(x) (x, x)" is unsafe which might introduce 
> side effects. Each MTL RxQ DMA channel mask is 4 bits, so using (0xf 
> << chan) instead of GENMASK(x + 3, x) to avoid unsafe macro.
> 
> Fixes: d43042f4da3e ("net: stmmac: mapping mtl rx to dma channel")

You need to point out an existing usage where this is causing problems, otherwise this is not a fix.

And squash the two patches together, it's going to be easier to review.