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SubjectRe: [PATCH v2 25/40] mmc: sdhci: Add a quirk to disable card clock during tuning
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On 10/08/18 21:08, Aapo Vienamo wrote:
> Add a quirk to disable card clock when the tuning command is sent.
>
> This has to be done to prevent the SDHCI controller from hanging on
> Tegra210. Without the quirk enabled there appears to be around 10%
> chance that the tuning sequence will fail and time out due to the
> controller locking up.
>
> Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>
> ---
> drivers/mmc/host/sdhci.c | 15 +++++++++++++++
> drivers/mmc/host/sdhci.h | 2 ++
> 2 files changed, 17 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 04dc443..166b16f 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2175,6 +2175,7 @@ static void sdhci_send_tuning(struct sdhci_host *host, u32 opcode)
> struct mmc_request mrq = {};
> unsigned long flags;
> u32 b = host->sdma_boundary;
> + u16 clk;
>
> spin_lock_irqsave(&host->lock, flags);
>
> @@ -2183,6 +2184,13 @@ static void sdhci_send_tuning(struct sdhci_host *host, u32 opcode)
> cmd.mrq = &mrq;
>
> mrq.cmd = &cmd;
> +
> + if (host->quirks2 & SDHCI_QUIRK2_TUNE_DIS_CARD_CLK) {
> + clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> + clk &= ~SDHCI_CLOCK_CARD_EN;
> + sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);

Rather than using a quirk, could you use the sdhci I/O accessors to disable
the clock before the tuning comment is written, udelay(1), and then enable
it again?

> + }
> +
> /*
> * In response to CMD19, the card sends 64 bytes of tuning
> * block to the Host Controller. So we set the block size
> @@ -2213,6 +2221,13 @@ static void sdhci_send_tuning(struct sdhci_host *host, u32 opcode)
> mmiowb();
> spin_unlock_irqrestore(&host->lock, flags);
>
> + if (host->quirks2 & SDHCI_QUIRK2_TUNE_DIS_CARD_CLK) {
> + udelay(1);
> + clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> + clk |= SDHCI_CLOCK_CARD_EN;
> + sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> + }
> +
> /* Wait for Buffer Read Ready interrupt */
> wait_event_timeout(host->buf_ready_int, (host->tuning_done == 1),
> msecs_to_jiffies(50));
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index 0a99008..cc411b0 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -452,6 +452,8 @@ struct sdhci_host {
> #define SDHCI_QUIRK2_DISABLE_HW_TIMEOUT (1<<17)
> /* Don't clear the SDHCI_TRANSFER_MODE register on tuning commands */
> #define SDHCI_QUIRK2_TUNE_SKIP_XFERMODE_REG_PROG (1<<18)
> +/* Disable card clock during tuning */
> +#define SDHCI_QUIRK2_TUNE_DIS_CARD_CLK (1<<19)
>
> int irq; /* Device IRQ */
> void __iomem *ioaddr; /* Mapped address */
>

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