by Andrea della Porta

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Subject: Re: [PATCH v3 3/4] mmc: sdhci-brcmstb: Add BCM2712 support

Hi Stefan,

On 08:59 Sat 25 May , Stefan Wahren wrote:
> Hi Andrea,
>
> Am 25.05.24 um 07:39 schrieb Andrea della Porta:
> > On 14:26 Tue 21 May , Stefan Wahren wrote:
> > > Hi Andrea,
> > >
> > > Am 21.05.24 um 10:35 schrieb Andrea della Porta:
> > > > Broadcom BCM2712 SoC has an SDHCI card controller using the SDIO CFG
> > > > register block present on other STB chips. Add support for BCM2712
> > > > SD capabilities of this chipset.
> > > > The silicon is SD Express capable but this driver port does not currently
> > > > include that feature yet.
> > > > Based on downstream driver by raspberry foundation maintained kernel.
> > > >
> > > > Signed-off-by: Andrea della Porta <[email protected]>
> > > > ---
> > > > drivers/mmc/host/sdhci-brcmstb.c | 65 ++++++++++++++++++++++++++++++++
> > > > 1 file changed, 65 insertions(+)
> > > >
> > > > diff --git a/drivers/mmc/host/sdhci-brcmstb.c b/drivers/mmc/host/sdhci-brcmstb.c
> > > > index 9053526fa212..b349262da36e 100644
> > > > --- a/drivers/mmc/host/sdhci-brcmstb.c
> > > > +++ b/drivers/mmc/host/sdhci-brcmstb.c
> > > > @@ -30,6 +30,21 @@
> > > >
> > > > #define SDHCI_ARASAN_CQE_BASE_ADDR 0x200
> > > >
> > > > +#define SDIO_CFG_CQ_CAPABILITY 0x4c
> > > > +#define SDIO_CFG_CQ_CAPABILITY_FMUL GENMASK(13, 12)
> > > > +
> > > > +#define SDIO_CFG_CTRL 0x0
> > > > +#define SDIO_CFG_CTRL_SDCD_N_TEST_EN BIT(31)
> > > > +#define SDIO_CFG_CTRL_SDCD_N_TEST_LEV BIT(30)
> > > > +
> > > > +#define SDIO_CFG_MAX_50MHZ_MODE 0x1ac
> > > > +#define SDIO_CFG_MAX_50MHZ_MODE_STRAP_OVERRIDE BIT(31)
> > > > +#define SDIO_CFG_MAX_50MHZ_MODE_ENABLE BIT(0)
> > > > +
> > > > +#define MMC_CAP_HSE_MASK (MMC_CAP2_HSX00_1_2V | MMC_CAP2_HSX00_1_8V)
> > > > +/* Select all SD UHS type I SDR speed above 50MB/s */
> > > > +#define MMC_CAP_UHS_I_SDR_MASK (MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR104)
> > > > +
> > > > struct sdhci_brcmstb_priv {
> > > > void __iomem *cfg_regs;
> > > > unsigned int flags;
> > > > @@ -38,6 +53,7 @@ struct sdhci_brcmstb_priv {
> > > > };
> > > >
> > > > struct brcmstb_match_priv {
> > > > + void (*cfginit)(struct sdhci_host *host);
> > > > void (*hs400es)(struct mmc_host *mmc, struct mmc_ios *ios);
> > > > struct sdhci_ops *ops;
> > > > const unsigned int flags;
> > > > @@ -168,6 +184,38 @@ static void sdhci_brcmstb_set_uhs_signaling(struct sdhci_host *host,
> > > > sdhci_writew(host, ctrl_2, SDHCI_HOST_CONTROL2);
> > > > }
> > > >
> > > > +static void sdhci_brcmstb_cfginit_2712(struct sdhci_host *host)
> > > > +{
> > > > + struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> > > > + struct sdhci_brcmstb_priv *brcmstb_priv = sdhci_pltfm_priv(pltfm_host);
> > > > + u32 reg, base_clk_mhz;
> > > > +
> > > > + /*
> > > > + * If we support a speed that requires tuning,
> > > > + * then select the delay line PHY as the clock source.
> > > > + */
> > > > + if ((host->mmc->caps & MMC_CAP_UHS_I_SDR_MASK) || (host->mmc->caps2 & MMC_CAP_HSE_MASK)) {
> > > > + reg = readl(brcmstb_priv->cfg_regs + SDIO_CFG_MAX_50MHZ_MODE);
> > > > + reg &= ~SDIO_CFG_MAX_50MHZ_MODE_ENABLE;
> > > > + reg |= SDIO_CFG_MAX_50MHZ_MODE_STRAP_OVERRIDE;
> > > > + writel(reg, brcmstb_priv->cfg_regs + SDIO_CFG_MAX_50MHZ_MODE);
> > > > + }
> > > > +
> > > > + if ((host->mmc->caps & MMC_CAP_NONREMOVABLE) ||
> > > > + (host->mmc->caps & MMC_CAP_NEEDS_POLL)) {
> > > > + /* Force presence */
> > > > + reg = readl(brcmstb_priv->cfg_regs + SDIO_CFG_CTRL);
> > > > + reg &= ~SDIO_CFG_CTRL_SDCD_N_TEST_LEV;
> > > > + reg |= SDIO_CFG_CTRL_SDCD_N_TEST_EN;
> > > > + writel(reg, brcmstb_priv->cfg_regs + SDIO_CFG_CTRL);
> > > > + }
> > > > +
> > > > + /* Guesstimate the timer frequency (controller base clock) */
> > > > + base_clk_mhz = max_t(u32, clk_get_rate(pltfm_host->clk) / (1000 * 1000), 1);
> > > > + reg = SDIO_CFG_CQ_CAPABILITY_FMUL | base_clk_mhz;
> > > > + writel(reg, brcmstb_priv->cfg_regs + SDIO_CFG_CQ_CAPABILITY);
> > > This part assumes the clock isn't changed afterwards, see below ...
> > > > +}
> > > > +
> > > > static void sdhci_brcmstb_dumpregs(struct mmc_host *mmc)
> > > > {
> > > > sdhci_dumpregs(mmc_priv(mmc));
> > > > @@ -200,6 +248,14 @@ static struct sdhci_ops sdhci_brcmstb_ops = {
> > > > .set_uhs_signaling = sdhci_set_uhs_signaling,
> > > > };
> > > >
> > > > +static struct sdhci_ops sdhci_brcmstb_ops_2712 = {
> > > > + .set_clock = sdhci_set_clock,
> > > > + .set_power = sdhci_set_power_and_bus_voltage,
> > > > + .set_bus_width = sdhci_set_bus_width,
> > > > + .reset = sdhci_reset,
> > > > + .set_uhs_signaling = sdhci_set_uhs_signaling,
> > > > +};
> > > > +
> > > > static struct sdhci_ops sdhci_brcmstb_ops_7216 = {
> > > > .set_clock = sdhci_brcmstb_set_clock,
> > > > .set_bus_width = sdhci_set_bus_width,
> > > > @@ -214,6 +270,11 @@ static struct sdhci_ops sdhci_brcmstb_ops_74165b0 = {
> > > > .set_uhs_signaling = sdhci_brcmstb_set_uhs_signaling,
> > > > };
> > > >
> > > > +static const struct brcmstb_match_priv match_priv_2712 = {
> > > > + .cfginit = sdhci_brcmstb_cfginit_2712,
> > > > + .ops = &sdhci_brcmstb_ops_2712,
> > > > +};
> > > > +
> > > > static struct brcmstb_match_priv match_priv_7425 = {
> > > > .flags = BRCMSTB_MATCH_FLAGS_NO_64BIT |
> > > > BRCMSTB_MATCH_FLAGS_BROKEN_TIMEOUT,
> > > > @@ -238,6 +299,7 @@ static struct brcmstb_match_priv match_priv_74165b0 = {
> > > > };
> > > >
> > > > static const struct of_device_id __maybe_unused sdhci_brcm_of_match[] = {
> > > > + { .compatible = "brcm,bcm2712-sdhci", .data = &match_priv_2712 },
> > > > { .compatible = "brcm,bcm7425-sdhci", .data = &match_priv_7425 },
> > > > { .compatible = "brcm,bcm7445-sdhci", .data = &match_priv_7445 },
> > > > { .compatible = "brcm,bcm7216-sdhci", .data = &match_priv_7216 },
> > > > @@ -370,6 +432,9 @@ static int sdhci_brcmstb_probe(struct platform_device *pdev)
> > > > (host->mmc->caps2 & MMC_CAP2_HS400_ES))
> > > > host->mmc_host_ops.hs400_enhanced_strobe = match_priv->hs400es;
> > > >
> > > > + if (match_priv->cfginit)
> > > > + match_priv->cfginit(host);
> > > > +
> > > I'm not sure this is the right place to call cfginit.
> > > sdhci_brcmstb_cfginit_2712 retrives the current controller base clock,
> > > but at the end of? sdhci_brcmstb_probe this clock frequency could be
> > > adjusted by the device property "clock-frequency". So i'm not sure this
> > > is intended.
> > I've tried to interpret the meaning of those two clocks since unfortunately I don't
> > own the datasheet for any of the platforms involved, so please take the following
> > as the result of my own (possibly wrong) intuition and (mostly wild) guessing.
> >
> > The main clock is 'sw_sdio' while 'sdio_freq' is optional and the latter seems to be
> > orthogonal to the former.
> > While sw_sdio is mostly used for SD storage card, sdio_freq seems more related to
> > SDIO family of cards (wifi, gps, camera, etc) for which you could specify a particular
> > (and higher) base frequency.
> > Unfortunately I wasn't able to find any reference to sdio_freq in current devicetree
> > so it's probably only specific to custom appliances: to be honest I'm not even sure
> > that BCM2712 is supporting that improved clock source. Also, from the following lines
> > at the end of cfginit function:
> >
> > /* Guesstimate the timer frequency (controller base clock) */
> > base_clk_mhz = max_t(u32, clk_get_rate(pltfm_host->clk) / (1000 * 1000), 1);
> > reg = SDIO_CFG_CQ_CAPABILITY_FMUL | base_clk_mhz;
> > writel(reg, brcmstb_priv->cfg_regs + SDIO_CFG_CQ_CAPABILITY);
> >
> > judging from the name of SDIO_CFG_CQ_CAPABILITY register, I'd guess that it relates
> > to some Command Queue (timeout?) setting so it's probably only important if CQE is
> > enabled specifying 'supports-cqe' property, which is not in current devicetree (nor
> > in downstream one). If this is the case it's mostly a performance improvement, and
> > as such something that we are not necessarily interested in right now since this
> > patchset adds just minimal boot support. I would then drop those lines, as we could
> > just reintroduce them if they need be once we have a better understanding of that
> > specific register and/if the cqe support will be enabled. As a matter of fact those
> > lines are not working as expected in any case since pltfm_host->clk is set at the
> > very end of sdhci_brcmstb_probe() while the cfginit function is invoked much earlier.
> > The result is that right now the value set ito SDIO_CFG_CQ_CAPABILITY register is always
> > equal to 1MHz. Further testing reveals that it is indeed working fine even with those
> > lines dropped, so I would deem that code as unnecessary for this early patchset.
> > Is it a viable solution?
> I don't have any knowledge about this hardware, so my opinion based on
> your good investigations. But i would be fine with this.
>
> Just to make it clear, this works with and without U-Boot in the bootchain?

Yes, I confirm it works with both.

Thanks,
Andrea

>
> Thanks
> >
> > Many thanks,
> > Andrea
> >
> > > > /*
> > > > * Supply the existing CAPS, but clear the UHS modes. This
> > > > * will allow these modes to be specified by device tree
>