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SubjectRe: [PATCH v2 11/40] mmc: sdhci: Add a quirk to skip clearing the transfer mode register on tuning
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On 10/08/18 21:08, Aapo Vienamo wrote:
> Add SDHCI_QUIRK2_TUNE_SKIP_XFERRMODE_REG_PROG to skip programming the
> SDHCI_TRANSFER_MODE in sdhci_set_transfer_mode() if tuning command is
> being sent.
>
> On Tegra210 and Tegra186 the tuning sequence hangs if the SDHCI
> transfer mode register is touched.
>
> Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>
> ---
> drivers/mmc/host/sdhci.c | 6 ++++++
> drivers/mmc/host/sdhci.h | 2 ++
> 2 files changed, 8 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index a7b5602..04dc443 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1028,6 +1028,12 @@ static void sdhci_set_transfer_mode(struct sdhci_host *host,
>
> if (data == NULL) {
> if (host->quirks2 &
> + SDHCI_QUIRK2_TUNE_SKIP_XFERMODE_REG_PROG &&
> + (cmd->opcode == MMC_SEND_TUNING_BLOCK ||
> + cmd->opcode == MMC_SEND_TUNING_BLOCK_HS200)) {
> + return;
> + }

Rather than introduce a quirk, can't we just dodge the unnecessary write e.g.

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 1b3fbd9bd5c5..68af6a67e397 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1033,10 +1033,19 @@ static void sdhci_set_transfer_mode(struct sdhci_host *host,
if (cmd->opcode != MMC_SEND_TUNING_BLOCK_HS200)
sdhci_writew(host, 0x0, SDHCI_TRANSFER_MODE);
} else {
- /* clear Auto CMD settings for no data CMDs */
+ u16 orig;
+
+ /* clear Auto CMD settings for no data CMDs */
mode = sdhci_readw(host, SDHCI_TRANSFER_MODE);
- sdhci_writew(host, mode & ~(SDHCI_TRNS_AUTO_CMD12 |
- SDHCI_TRNS_AUTO_CMD23), SDHCI_TRANSFER_MODE);
+ orig = mode;
+ mode &= ~(SDHCI_TRNS_AUTO_CMD12 | SDHCI_TRNS_AUTO_CMD23);
+ /*
+ * Do not write transfer mode unnecessarily because it
+ * can upset some host controllers (e.g. sdhci-tregra)
+ * during tuning.
+ */
+ if (mode != orig)
+ sdhci_writew(host, new_mode, SDHCI_TRANSFER_MODE);
}
return;
}

Alternatively

> + if (host->quirks2 &
> SDHCI_QUIRK2_CLEAR_TRANSFERMODE_REG_BEFORE_CMD) {
> sdhci_writew(host, 0x0, SDHCI_TRANSFER_MODE);
> } else {
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index 23966f8..0a99008 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -450,6 +450,8 @@ struct sdhci_host {
> * obtainable timeout.
> */
> #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)
>
> int irq; /* Device IRQ */
> void __iomem *ioaddr; /* Mapped address */
>

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