* [PATCH] sunxi: mmc: A20: Fix MMC optimisation
@ 2021-09-03 15:49 Andre Przywara
2021-09-04 10:38 ` Jaehoon Chung
0 siblings, 1 reply; 2+ messages in thread
From: Andre Przywara @ 2021-09-03 15:49 UTC (permalink / raw)
To: Jagan Teki, Tom Rini; +Cc: Jernej Skrabec, Samuel Holland, u-boot, linux-sunxi
Some SoCs (as seen on A20) seem to misreport the MMC FIFO level if the
FIFO is completely full: the level size reads as zero, but the FIFO_FULL
bit is set. We won't do a single iteration of the read loop in this
case, so will be stuck forever.
Check for this situation and use a safe minimal FIFO size instead when
we hit this case.
This fixes MMC boot on A20 devices after the MMC FIFO optimisation
(9faae5457f52).
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
drivers/mmc/sunxi_mmc.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/mmc/sunxi_mmc.c b/drivers/mmc/sunxi_mmc.c
index 178b8cf106..aaab0cf866 100644
--- a/drivers/mmc/sunxi_mmc.c
+++ b/drivers/mmc/sunxi_mmc.c
@@ -349,10 +349,14 @@ static int mmc_trans_data_by_cpu(struct sunxi_mmc_priv *priv, struct mmc *mmc,
* register without checking the status register after every
* read. That saves half of the costly MMIO reads, effectively
* doubling the read performance.
+ * Some SoCs (A20) report a level of 0 if the FIFO is
+ * completely full (value masked out?). Use a safe minimal
+ * FIFO size in this case.
*/
- for (in_fifo = SUNXI_MMC_STATUS_FIFO_LEVEL(status);
- in_fifo > 0;
- in_fifo--)
+ in_fifo = SUNXI_MMC_STATUS_FIFO_LEVEL(status);
+ if (in_fifo == 0 && (status & SUNXI_MMC_STATUS_FIFO_FULL))
+ in_fifo = 32;
+ for (; in_fifo > 0; in_fifo--)
buff[i++] = readl_relaxed(&priv->reg->fifo);
dmb();
}
--
2.17.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] sunxi: mmc: A20: Fix MMC optimisation
2021-09-03 15:49 [PATCH] sunxi: mmc: A20: Fix MMC optimisation Andre Przywara
@ 2021-09-04 10:38 ` Jaehoon Chung
0 siblings, 0 replies; 2+ messages in thread
From: Jaehoon Chung @ 2021-09-04 10:38 UTC (permalink / raw)
To: Andre Przywara, Jagan Teki, Tom Rini
Cc: Jernej Skrabec, Samuel Holland, u-boot, linux-sunxi
Andre Przywara wrote on 9/4/21 12:49 AM:
> Some SoCs (as seen on A20) seem to misreport the MMC FIFO level if the
> FIFO is completely full: the level size reads as zero, but the FIFO_FULL
> bit is set. We won't do a single iteration of the read loop in this
> case, so will be stuck forever.
>
> Check for this situation and use a safe minimal FIFO size instead when
> we hit this case.
>
> This fixes MMC boot on A20 devices after the MMC FIFO optimisation
> (9faae5457f52).
>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Best Regards,
Jaehoon Chung
> ---
> drivers/mmc/sunxi_mmc.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mmc/sunxi_mmc.c b/drivers/mmc/sunxi_mmc.c
> index 178b8cf106..aaab0cf866 100644
> --- a/drivers/mmc/sunxi_mmc.c
> +++ b/drivers/mmc/sunxi_mmc.c
> @@ -349,10 +349,14 @@ static int mmc_trans_data_by_cpu(struct sunxi_mmc_priv *priv, struct mmc *mmc,
> * register without checking the status register after every
> * read. That saves half of the costly MMIO reads, effectively
> * doubling the read performance.
> + * Some SoCs (A20) report a level of 0 if the FIFO is
> + * completely full (value masked out?). Use a safe minimal
> + * FIFO size in this case.
> */
> - for (in_fifo = SUNXI_MMC_STATUS_FIFO_LEVEL(status);
> - in_fifo > 0;
> - in_fifo--)
> + in_fifo = SUNXI_MMC_STATUS_FIFO_LEVEL(status);
> + if (in_fifo == 0 && (status & SUNXI_MMC_STATUS_FIFO_FULL))
> + in_fifo = 32;
> + for (; in_fifo > 0; in_fifo--)
> buff[i++] = readl_relaxed(&priv->reg->fifo);
> dmb();
> }
^ permalink raw reply [flat|nested] 2+ messages in thread
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