Re: [RFC PATCH v3.1 12/27] mmc: sdhci-uhs2: add reset function

Adrian Hunter
2020-11-26T08:16:42Z

On 6/11/20 4:27 am, AKASHI Takahiro wrote:
> Sdhci_uhs2_reset() does a UHS-II specific reset operation.
>
> Signed-off-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> ---
> drivers/mmc/host/sdhci-uhs2.c | 49 +++++++++++++++++++++++++++++++++++
> drivers/mmc/host/sdhci-uhs2.h | 1 +
> drivers/mmc/host/sdhci.c | 3 ++-
> drivers/mmc/host/sdhci.h | 1 +
> 4 files changed, 53 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
> index 08905ed081fb..e2b9743fe17d 100644
> --- a/drivers/mmc/host/sdhci-uhs2.c
> +++ b/drivers/mmc/host/sdhci-uhs2.c
> @@ -10,6 +10,7 @@
> * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
> */
>
> +#include <linux/delay.h>
> #include <linux/module.h>
>
> #include "sdhci.h"
> @@ -49,6 +50,54 @@ void sdhci_uhs2_dump_regs(struct sdhci_host *host)
> }
> EXPORT_SYMBOL_GPL(sdhci_uhs2_dump_regs);
>
> +/*****************************************************************************\
> + * *
> + * Low level functions *
> + * *
> +\*****************************************************************************/
> +
> +/**
> + * sdhci_uhs2_reset - invoke SW reset
> + * @host: SDHCI host
> + * @mask: Control mask
> + *
> + * Invoke SW reset, depending on a bit in @mask and wait for completion.
> + */
> +void sdhci_uhs2_reset(struct sdhci_host *host, u16 mask)
> +{
> + unsigned long timeout;
> +
> + if (!(host->mmc->caps & MMC_CAP_UHS2))

Please make a helper so this can be like:

if (!sdhci_uhs2_mode(host))

The capability will be always present for hosts that support UHS2, but not
all cards support UHS2 mode. I suggest just adding a bool to struct
sdhci_host to keep track of when the host is in UHS2 mode.

> + return;
> +
> + sdhci_writew(host, mask, SDHCI_UHS2_SW_RESET);
> +
> + if (mask & SDHCI_UHS2_SW_RESET_FULL) {
> + host->clock = 0;
> + /* Reset-all turns off SD Bus Power */
> + if (host->quirks2 & SDHCI_QUIRK2_CARD_ON_NEEDS_BUS_ON)

I would prefer not to support any legacy quirks that we do not need right
now. Just be sure to add a comment somewhere listing which quirks are not
supported for UHS2 host controllers.

> + sdhci_runtime_pm_bus_off(host);
> + }
> +
> + /* Wait max 100 ms */
> + timeout = 10000;
> +
> + /* hw clears the bit when it's done */
> + while (sdhci_readw(host, SDHCI_UHS2_SW_RESET) & mask) {

This kind of loop can now be done with read_poll_timeout_atomic(sdhci_readw,
..., host, SDHCI_UHS2_SW_RESET)

> + if (timeout == 0) {
> + pr_err("%s: %s: Reset 0x%x never completed.\n",
> + __func__, mmc_hostname(host->mmc), (int)mask);
> + pr_err("%s: clean reset bit\n",
> + mmc_hostname(host->mmc));
> + sdhci_writeb(host, 0, SDHCI_UHS2_SW_RESET);
> + return;
> + }
> + timeout--;
> + udelay(10);
> + }
> +}
> +EXPORT_SYMBOL_GPL(sdhci_uhs2_reset);
> +
> /*****************************************************************************\
> * *
> * Driver init/exit *
> diff --git a/drivers/mmc/host/sdhci-uhs2.h b/drivers/mmc/host/sdhci-uhs2.h
> index b9529d32b58d..7bb7a0d67109 100644
> --- a/drivers/mmc/host/sdhci-uhs2.h
> +++ b/drivers/mmc/host/sdhci-uhs2.h
> @@ -210,5 +210,6 @@
> struct sdhci_host;
>
> void sdhci_uhs2_dump_regs(struct sdhci_host *host);
> +void sdhci_uhs2_reset(struct sdhci_host *host, u16 mask);
>
> #endif /* __SDHCI_UHS2_H */
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index d4a57e8c9bb8..af336bdb4305 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -195,13 +195,14 @@ static void sdhci_runtime_pm_bus_on(struct sdhci_host *host)
> pm_runtime_get_noresume(host->mmc->parent);
> }
>
> -static void sdhci_runtime_pm_bus_off(struct sdhci_host *host)
> +void sdhci_runtime_pm_bus_off(struct sdhci_host *host)
> {
> if (!host->bus_on)
> return;
> host->bus_on = false;
> pm_runtime_put_noidle(host->mmc->parent);
> }
> +EXPORT_SYMBOL_GPL(sdhci_runtime_pm_bus_off);
>
> void sdhci_reset(struct sdhci_host *host, u8 mask)
> {
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index d9d7a76cedc1..b9932423db08 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -831,6 +831,7 @@ static inline void sdhci_read_caps(struct sdhci_host *host)
> __sdhci_read_caps(host, NULL, NULL, NULL);
> }
>
> +void sdhci_runtime_pm_bus_off(struct sdhci_host *host);
> u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
> unsigned int *actual_clock);
> void sdhci_set_clock(struct sdhci_host *host, unsigned int clock);
>