On Thu 20 Feb 01:20 PST 2020, Sayali Lokhande wrote:
> From: Ram Prakash Gupta <rampraka@xxxxxxxxxxxxxx>
>
> During GCC level clock gating of MCLK, the async FIFO
> gets into some hang condition, such that for the next
> transfer after MCLK ungating, first bit of CMD response
> doesn't get written in to the FIFO. This cause the CPSM
> to hang eventually leading to SW timeout.
Does this always happen, on what platforms does this happen? How does
this manifest itself? Can you please elaborate.
>
> To fix the issue, toggle the FIFO write clock after
> MCLK ungated to get the FIFO pointers and flags to
> valid states.
>
> Change-Id: Ibef2d1d283ac0b6983c609a4abc98bc574d31fa6
Please drop the Change-Id and please add
Cc: stable@xxxxxxxxxxxxxxx
If this is a bug fix that should be backported to e.g. 5.4.
> Signed-off-by: Ram Prakash Gupta <rampraka@xxxxxxxxxxxxxx>
> Signed-off-by: Sayali Lokhande <sayalil@xxxxxxxxxxxxxx>
> ---
> drivers/mmc/host/sdhci-msm.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index c3a160c..eaa3e95 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -127,6 +127,8 @@
> #define CQHCI_VENDOR_CFG1 0xA00
> #define CQHCI_VENDOR_DIS_RST_ON_CQ_EN (0x3 << 13)
>
> +#define RCLK_TOGGLE 0x2
Please use BIT(1) instead.
> +
> struct sdhci_msm_offset {
> u32 core_hc_mode;
> u32 core_mci_data_cnt;
> @@ -1554,6 +1556,43 @@ static void __sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
> sdhci_enable_clk(host, clk);
> }
>
> +/*
> + * After MCLK ugating, toggle the FIFO write clock to get
> + * the FIFO pointers and flags to valid state.
> + */
> +static void sdhci_msm_toggle_fifo_write_clk(struct sdhci_host *host)
> +{
> + struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> + struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> + const struct sdhci_msm_offset *msm_offset =
> + msm_host->offset;
This doesn't look to be > 80 chars, please unwrap.
> + struct mmc_card *card = host->mmc->card;
> +
> + if (msm_host->tuning_done ||
> + (card && card->ext_csd.strobe_support &&
> + card->host->ios.enhanced_strobe)) {
> + /*
> + * set HC_REG_DLL_CONFIG_3[1] to select MCLK as
> + * DLL input clock
You can shorten this to /* Select MCLK as DLL input clock */ if you make
the below readl/writel a little bit easier to read.
> + */
> + writel_relaxed(((readl_relaxed(host->ioaddr +
> + msm_offset->core_dll_config_3))
> + | RCLK_TOGGLE), host->ioaddr +
> + msm_offset->core_dll_config_3);
Please use a local variable and write this out as:
val = readl(addr);
val |= RCLK_TOGGLE;
writel(val, addr);
> + /* ensure above write as toggling same bit quickly */
> + wmb();
This ensures ordering of writes, if you want to make sure the write has
hit the hardware before the delay perform a readl() on the address.
> + udelay(2);
> + /*
> + * clear HC_REG_DLL_CONFIG_3[1] to select RCLK as
> + * DLL input clock
> + */
/* Select RCLK as DLL input clock */
> + writel_relaxed(((readl_relaxed(host->ioaddr +
> + msm_offset->core_dll_config_3))
> + & ~RCLK_TOGGLE), host->ioaddr +
> + msm_offset->core_dll_config_3);
Same as above, readl(); val &= ~RCLK_TOGGLE; writel(); will make this
easier on the eyes.
> + }
> +}
> +
> /* sdhci_msm_set_clock - Called with (host->lock) spinlock held. */
> static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
> {
> @@ -2149,6 +2188,10 @@ static __maybe_unused int sdhci_msm_runtime_resume(struct device *dev)
> msm_host->bulk_clks);
> if (ret)
> return ret;
An empty line please.
> + if (host->mmc &&
Afaict host->mmc can't be NULL, can you please confirm that you need
this check.
> + (host->mmc->ios.timing == MMC_TIMING_MMC_HS400))
> + sdhci_msm_toggle_fifo_write_clk(host);
> +
Regards,
Bjorn
> /*
> * Whenever core-clock is gated dynamically, it's needed to
> * restore the SDR DLL settings when the clock is ungated.
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
