linux-kernel - Re: [PATCH 3/11] memory: tegra: add flush operation for Tegra124 memory clients

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Message-ID: <20150106150744.GB18598@nvidia.com>
Date:	Tue, 6 Jan 2015 23:07:45 +0800
From:	Vince Hsu <vinceh@...dia.com>
To:	Thierry Reding <thierry.reding@...il.com>
CC:	<swarren@...dotorg.org>, <gnurou@...il.com>, <bskeggs@...hat.com>,
	<martin.peres@...e.fr>, <seven@...rod-online.com>,
	<samuel.pitoiset@...il.com>, <nouveau@...ts.freedesktop.org>,
	<linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/11] memory: tegra: add flush operation for Tegra124
 memory clients

On 03:30:00PM Jan 06, Thierry Reding wrote:
> * PGP Signed by an unknown key
> 
> On Tue, Dec 23, 2014 at 06:39:56PM +0800, Vince Hsu wrote:
> > Signed-off-by: Vince Hsu <vinceh@...dia.com>
> > ---
> >  drivers/memory/tegra/tegra124.c | 82 +++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 82 insertions(+)
> > 
> > diff --git a/drivers/memory/tegra/tegra124.c b/drivers/memory/tegra/tegra124.c
> > index 278d40b854c1..036935743a0a 100644
> > --- a/drivers/memory/tegra/tegra124.c
> > +++ b/drivers/memory/tegra/tegra124.c
> > @@ -6,6 +6,7 @@
> >   * published by the Free Software Foundation.
> >   */
> >  
> > +#include <linux/delay.h>
> >  #include <linux/of.h>
> >  #include <linux/mm.h>
> >  
> > @@ -959,7 +960,85 @@ static const struct tegra_smmu_swgroup tegra124_swgroups[] = {
> >  	{ .swgroup = TEGRA_SWGROUP_VI,        .reg = 0x280 },
> >  };
> >  
> > +static const struct tegra_mc_hr tegra124_mc_hr[] = {
> > +	{TEGRA_SWGROUP_AFI,        0x200, 0x200,  0},
> > +	{TEGRA_SWGROUP_AVPC,       0x200, 0x200,  1},
> > +	{TEGRA_SWGROUP_DC,         0x200, 0x200,  2},
> > +	{TEGRA_SWGROUP_DCB,        0x200, 0x200,  3},
> > +	{TEGRA_SWGROUP_HC,         0x200, 0x200,  6},
> > +	{TEGRA_SWGROUP_HDA,        0x200, 0x200,  7},
> > +	{TEGRA_SWGROUP_ISP2,       0x200, 0x200,  8},
> > +	{TEGRA_SWGROUP_MPCORE,     0x200, 0x200,  9},
> > +	{TEGRA_SWGROUP_MPCORELP,   0x200, 0x200, 10},
> > +	{TEGRA_SWGROUP_MSENC,      0x200, 0x200, 11},
> > +	{TEGRA_SWGROUP_PPCS,       0x200, 0x200, 14},
> > +	{TEGRA_SWGROUP_SATA,       0x200, 0x200, 15},
> > +	{TEGRA_SWGROUP_VDE,        0x200, 0x200, 16},
> > +	{TEGRA_SWGROUP_VI,         0x200, 0x200, 17},
> > +	{TEGRA_SWGROUP_VIC,        0x200, 0x200, 18},
> > +	{TEGRA_SWGROUP_XUSB_HOST,  0x200, 0x200, 19},
> > +	{TEGRA_SWGROUP_XUSB_DEV,   0x200, 0x200, 20},
> > +	{TEGRA_SWGROUP_TSEC,       0x200, 0x200, 22},
> > +	{TEGRA_SWGROUP_SDMMC1A,    0x200, 0x200, 29},
> > +	{TEGRA_SWGROUP_SDMMC2A,    0x200, 0x200, 30},
> > +	{TEGRA_SWGROUP_SDMMC3A,    0x200, 0x200, 31},
> 
> The documentation that I have says that the status register for these is
> 0x204.
Oops. Thanks for catching this. Will fix.

> 
> > +	{TEGRA_SWGROUP_SDMMC4A,    0x970, 0x974,  0},
> > +	{TEGRA_SWGROUP_ISP2B,      0x970, 0x974,  1},
> > +	{TEGRA_SWGROUP_GPU,        0x970, 0x974,  2},
> > +};
> > +
> >  #ifdef CONFIG_ARCH_TEGRA_124_SOC
> > +
> > +static bool tegra124_stable_hotreset_check(struct tegra_mc *mc,
> > +		u32 reg, u32 *stat)
> > +{
> > +	int i;
> > +	u32 cur_stat;
> > +	u32 prv_stat;
> > +
> > +	prv_stat = mc_readl(mc, reg);
> > +	for (i = 0; i < 5; i++) {
> > +		cur_stat = mc_readl(mc, reg);
> > +		if (cur_stat != prv_stat)
> > +			return false;
> > +	}
> 
> Why this loop? The function is already called in a polling loop below.
> Also why compare to the previous value of the register? Isn't the only
> thing we're interested in the value of the specific bit?
I recall it's due to a HW bug that there might be a gitch if we program
the ctrl reg and then read the status reg in a short window. This function
is to make sure we have a stable status.

> 
> > +	*stat = cur_stat;
> > +	return true;
> > +}
> > +
> > +static int tegra124_mc_flush(struct tegra_mc *mc,
> > +		const struct tegra_mc_hr *hr_client, bool enable)
> > +{
> > +	u32 val;
> > +
> > +	if (!mc || !hr_client)
> > +		return -EINVAL;
> > +
> > +	val = mc_readl(mc, hr_client->ctrl);
> > +	if (enable)
> > +		val |= BIT(hr_client->bit);
> > +	else
> > +		val &= ~BIT(hr_client->bit);
> > +	mc_writel(mc, val, hr_client->ctrl);
> > +	mc_readl(mc, hr_client->ctrl);
> > +
> > +	/* poll till the flush is done */
> > +	if (enable) {
> > +		do {
> > +			udelay(10);
> 
> This should probably be usleep_range(10, 20) or something.
Maybe no. We might need some spin lock here to ensure only one flushing
operation requested and no race could happen.

> 
> Would it be difficult to implement this for Tegra30 and Tegra114?
No. But I have to check the detail in Tegra30 and Tegra114. And the biggest
problem is I don't have the boards to test.

Thanks,
Vince

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