On Mon, Feb 27, 2017 at 12:09:02PM +0200, Mikko Perttunen wrote:
> On 23.02.2017 19:24, Thierry Reding wrote:
> > From: Thierry Reding <[email protected]>
> >
> > Program the receive queue size based on the RX FIFO size and enable
> > hardware flow control for large FIFOs.
> >
> > Signed-off-by: Thierry Reding <[email protected]>
> > ---
> > drivers/net/ethernet/stmicro/stmmac/dwmac4.h | 12 +++++++
> > drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c | 43 ++++++++++++++++++++++--
> > 2 files changed, 53 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
> > index db45134fddf0..9acc1f1252b3 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
> > @@ -180,6 +180,7 @@ enum power_event {
> > #define MTL_OP_MODE_TSF BIT(1)
> >
> > #define MTL_OP_MODE_TQS_MASK GENMASK(24, 16)
> > +#define MTL_OP_MODE_TQS_SHIFT 16
> >
> > #define MTL_OP_MODE_TTC_MASK 0x70
> > #define MTL_OP_MODE_TTC_SHIFT 4
> > @@ -193,6 +194,17 @@ enum power_event {
> > #define MTL_OP_MODE_TTC_384 (6 << MTL_OP_MODE_TTC_SHIFT)
> > #define MTL_OP_MODE_TTC_512 (7 << MTL_OP_MODE_TTC_SHIFT)
> >
> > +#define MTL_OP_MODE_RQS_MASK GENMASK(29, 20)
> > +#define MTL_OP_MODE_RQS_SHIFT 20
> > +
> > +#define MTL_OP_MODE_RFD_MASK GENMASK(19, 14)
> > +#define MTL_OP_MODE_RFD_SHIFT 14
> > +
> > +#define MTL_OP_MODE_RFA_MASK GENMASK(13, 8)
> > +#define MTL_OP_MODE_RFA_SHIFT 8
> > +
> > +#define MTL_OP_MODE_EHFC BIT(7)
> > +
> > #define MTL_OP_MODE_RTC_MASK 0x18
> > #define MTL_OP_MODE_RTC_SHIFT 3
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
> > index 8d249f3b34c8..03d230201960 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
> > @@ -185,8 +185,9 @@ static void dwmac4_rx_watchdog(void __iomem *ioaddr, u32 riwt)
> > }
> >
> > static void dwmac4_dma_chan_op_mode(void __iomem *ioaddr, int txmode,
> > - int rxmode, u32 channel)
> > + int rxmode, u32 channel, int rxfifosz)
> > {
> > + unsigned int rqs = rxfifosz / 256 - 1;
> > u32 mtl_tx_op, mtl_rx_op, mtl_rx_int;
> >
> > /* Following code only done for channel 0, other channels not yet
> > @@ -252,6 +253,44 @@ static void dwmac4_dma_chan_op_mode(void __iomem *ioaddr, int txmode,
> > mtl_rx_op |= MTL_OP_MODE_RTC_128;
> > }
> >
> > + mtl_rx_op &= ~MTL_OP_MODE_RQS_MASK;
> > + mtl_rx_op |= rqs << MTL_OP_MODE_RQS_SHIFT;
> > +
> > + /* enable flow control only if each channel gets 4 KiB or more FIFO */
> > + if (rxfifosz >= 4096) {
> > + unsigned int rfd, rfa;
> > +
> > + mtl_rx_op |= MTL_OP_MODE_EHFC;
> > +
> > + switch (rxfifosz) {
> > + case 4096:
> > + rfd = 0x03;
> > + rfa = 0x01;
> > + break;
> > +
> > + case 8192:
> > + rfd = 0x06;
> > + rfa = 0x0a;
> > + break;
> > +
> > + case 16384:
> > + rfd = 0x06;
> > + rfa = 0x12;
> > + break;
> > +
> > + default:
> > + rfd = 0x06;
> > + rfa = 0x1e;
> > + break;
> > + }
>
> Are these values correct? In the 4096 case, rfd > rfa, in all other cases
> the other way around. In any case it would be useful to have a comment
> clarifying the thresholds in bytes.
I'll investigate. To be honest I simply took this from Stephen's U-Boot
driver since that's already tested. I trust Stephen, so I didn't bother
double-checking.
Thierry
On 03/09/2017 12:42 PM, Thierry Reding wrote:
> On Mon, Feb 27, 2017 at 12:09:02PM +0200, Mikko Perttunen wrote:
>> On 23.02.2017 19:24, Thierry Reding wrote:
>>> From: Thierry Reding <[email protected]>
>>>
>>> Program the receive queue size based on the RX FIFO size and enable
>>> hardware flow control for large FIFOs.
>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
>>> @@ -252,6 +253,44 @@ static void dwmac4_dma_chan_op_mode(void __iomem *ioaddr, int txmode,
>>> mtl_rx_op |= MTL_OP_MODE_RTC_128;
>>> }
>>>
>>> + mtl_rx_op &= ~MTL_OP_MODE_RQS_MASK;
>>> + mtl_rx_op |= rqs << MTL_OP_MODE_RQS_SHIFT;
>>> +
>>> + /* enable flow control only if each channel gets 4 KiB or more FIFO */
>>> + if (rxfifosz >= 4096) {
>>> + unsigned int rfd, rfa;
>>> +
>>> + mtl_rx_op |= MTL_OP_MODE_EHFC;
>>> +
>>> + switch (rxfifosz) {
>>> + case 4096:
>>> + rfd = 0x03;
>>> + rfa = 0x01;
>>> + break;
>>> +
>>> + case 8192:
>>> + rfd = 0x06;
>>> + rfa = 0x0a;
>>> + break;
>>> +
>>> + case 16384:
>>> + rfd = 0x06;
>>> + rfa = 0x12;
>>> + break;
>>> +
>>> + default:
>>> + rfd = 0x06;
>>> + rfa = 0x1e;
>>> + break;
>>> + }
>>
>> Are these values correct? In the 4096 case, rfd > rfa, in all other cases
>> the other way around. In any case it would be useful to have a comment
>> clarifying the thresholds in bytes.
>
> I'll investigate. To be honest I simply took this from Stephen's U-Boot
> driver since that's already tested. I trust Stephen, so I didn't bother
> double-checking.
I don't recall for sure, but I think these values came directly from
either the upstream kernel (the non-stmmac driver) or NV downstream
kernel EQoS driver, and I re-used them without investigating. I'm not
even sure if the outer if() expression is true; these numbers might not
even end up being used?
On Thu, Mar 09, 2017 at 01:18:11PM -0700, Stephen Warren wrote:
> On 03/09/2017 12:42 PM, Thierry Reding wrote:
> > On Mon, Feb 27, 2017 at 12:09:02PM +0200, Mikko Perttunen wrote:
> > > On 23.02.2017 19:24, Thierry Reding wrote:
> > > > From: Thierry Reding <[email protected]>
> > > >
> > > > Program the receive queue size based on the RX FIFO size and enable
> > > > hardware flow control for large FIFOs.
>
> > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
>
> > > > @@ -252,6 +253,44 @@ static void dwmac4_dma_chan_op_mode(void __iomem *ioaddr, int txmode,
> > > > mtl_rx_op |= MTL_OP_MODE_RTC_128;
> > > > }
> > > >
> > > > + mtl_rx_op &= ~MTL_OP_MODE_RQS_MASK;
> > > > + mtl_rx_op |= rqs << MTL_OP_MODE_RQS_SHIFT;
> > > > +
> > > > + /* enable flow control only if each channel gets 4 KiB or more FIFO */
> > > > + if (rxfifosz >= 4096) {
> > > > + unsigned int rfd, rfa;
> > > > +
> > > > + mtl_rx_op |= MTL_OP_MODE_EHFC;
> > > > +
> > > > + switch (rxfifosz) {
> > > > + case 4096:
> > > > + rfd = 0x03;
> > > > + rfa = 0x01;
> > > > + break;
> > > > +
> > > > + case 8192:
> > > > + rfd = 0x06;
> > > > + rfa = 0x0a;
> > > > + break;
> > > > +
> > > > + case 16384:
> > > > + rfd = 0x06;
> > > > + rfa = 0x12;
> > > > + break;
> > > > +
> > > > + default:
> > > > + rfd = 0x06;
> > > > + rfa = 0x1e;
> > > > + break;
> > > > + }
> > >
> > > Are these values correct? In the 4096 case, rfd > rfa, in all other cases
> > > the other way around. In any case it would be useful to have a comment
> > > clarifying the thresholds in bytes.
> >
> > I'll investigate. To be honest I simply took this from Stephen's U-Boot
> > driver since that's already tested. I trust Stephen, so I didn't bother
> > double-checking.
>
> I don't recall for sure, but I think these values came directly from either
> the upstream kernel (the non-stmmac driver) or NV downstream kernel EQoS
> driver, and I re-used them without investigating. I'm not even sure if the
> outer if() expression is true; these numbers might not even end up being
> used?
Yes they are, and they were even the key to making the STMMAC driver
work on Tegra186. Without programming these fields the driver would fail
to receive any packets.
I noticed that you had comments in the U-Boot driver that I had left out
(most likely because I forgot to add them after cleaning up after the
hacking session). Here's the original extract from U-Boot:
/*
* Set Threshold for Activating Flow Contol space for min 2
* frames ie, (1500 * 1) = 1500 bytes.
*
* Set Threshold for Deactivating Flow Contol for space of
* min 1 frame (frame size 1500bytes) in receive fifo
*/
if (rqs == ((4096 / 256) - 1)) {
/*
* This violates the above formula because of FIFO size
* limit therefore overflow may occur inspite of this.
*/
rfd = 0x3; /* Full-3K */
rfa = 0x1; /* Full-1.5K */
} else if (rqs == ((8192 / 256) - 1)) {
rfd = 0x6; /* Full-4K */
rfa = 0xa; /* Full-6K */
} else if (rqs == ((16384 / 256) - 1)) {
rfd = 0x6; /* Full-4K */
rfa = 0x12; /* Full-10K */
} else {
rfd = 0x6; /* Full-4K */
rfa = 0x1E; /* Full-16K */
}
Two things are strange about this:
1) the first comment says "2 frames", but the threshold value is
clearly just one frame
2) the first set of rfd/rfa values has a wrong comment, by my
understanding: Full-3K should really be Full-2.5K
The encoding of these values is essentially:
threshold = full - (1K + value * 0.5K)
Here's my updated version from the kernel driver:
/*
* Set Threshold for Activating Flow Control to min 2 frames,
* i.e. 1500 * 2 = 3000 bytes.
*
* Set Threshold for Deactivating Flow Control to min 1 frame,
* i.e. 1500 bytes.
*/
switch (rxfifosz) {
case 4096:
/*
* This violates the above formula because of FIFO size
* limit therefore overflow may occur in spite of this.
*/
rfd = 0x03; /* Full-2.5K */
rfa = 0x01; /* Full-1.5K */
break;
case 8192:
rfd = 0x06; /* Full-4K */
rfa = 0x0a; /* Full-6K */
break;
case 16384:
rfd = 0x06; /* Full-4K */
rfa = 0x12; /* Full-10K */
break;
default:
rfd = 0x06; /* Full-4K */
rfa = 0x1e; /* Full-16K */
break;
}
As best as I can tell these values are within the constraints given in
the TRM and they also make sense to me for the purposes they're used
for.
Thierry