RE: [PATCH v2] mmc: mtk-sd: increase the minimum bus frequency

[Peng Fan (OSS)]

> Subject: [PATCH v2] mmc: mtk-sd: increase the minimum bus frequency

Could you please rebase? I am not able to apply this patch.

Thanks,
Peng.

> 
> With a 48MHz input clock, the lowest bus frequency can be as low as
> 4800 / (4 * 4095) = 2930Hz. Such an extremely low frequency will cause
> the mmc framework take seconds to finish the initialization.
> 
> Limiting the minimum bus frequency to a slightly higher value can solve the
> issue without any side effects.
> 
> Signed-off-by: Weijie Gao 
> ---
>  drivers/mmc/mtk-sd.c | 5 +
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/mmc/mtk-sd.c b/drivers/mmc/mtk-sd.c index
> 3b9c122..626a4d3 100644
> --- a/drivers/mmc/mtk-sd.c
> +++ b/drivers/mmc/mtk-sd.c
> @@ -232,6 +232,8 @@
> 
>  #define SCLK_CYCLES_SHIFT20
> 
> +#define MIN_BUS_CLK  20
> +
>  #define CMD_INTS_MASK\
>   (MSDC_INT_CMDRDY | MSDC_INT_RSPCRCERR |
> MSDC_INT_CMDTMO)
> 
> @@ -1639,6 +1641,9 @@ static int msdc_drv_probe(struct udevice *dev)
>   else
>   cfg->f_min = host->src_clk_freq / (4 * 4095);
> 
> + if (cfg->f_min < MIN_BUS_CLK)
> + cfg->f_min = MIN_BUS_CLK;
> +
>   cfg->f_max = host->src_clk_freq;
> 
>   cfg->b_max = 1024;
> --
> 1.9.1

Re: [PATCH v2] mmc: mtk-sd: increase the minimum bus frequency

[Jaehoon Chung]

On 3/5/21 12:24 PM, Weijie Gao wrote:
> With a 48MHz input clock, the lowest bus frequency can be as low as
> 4800 / (4 * 4095) = 2930Hz. Such an extremely low frequency will cause
> the mmc framework take seconds to finish the initialization.
> 
> Limiting the minimum bus frequency to a slightly higher value can solve the
> issue without any side effects.
> 
> Signed-off-by: Weijie Gao 

Reviewed-by: Jaehoon Chung 

Best Regards,
Jaehoon Chung

> ---
>  drivers/mmc/mtk-sd.c | 5 +
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/mmc/mtk-sd.c b/drivers/mmc/mtk-sd.c
> index 3b9c122..626a4d3 100644
> --- a/drivers/mmc/mtk-sd.c
> +++ b/drivers/mmc/mtk-sd.c
> @@ -232,6 +232,8 @@
>  
>  #define SCLK_CYCLES_SHIFT20
>  
> +#define MIN_BUS_CLK  20
> +
>  #define CMD_INTS_MASK\
>   (MSDC_INT_CMDRDY | MSDC_INT_RSPCRCERR | MSDC_INT_CMDTMO)
>  
> @@ -1639,6 +1641,9 @@ static int msdc_drv_probe(struct udevice *dev)
>   else
>   cfg->f_min = host->src_clk_freq / (4 * 4095);
>  
> + if (cfg->f_min < MIN_BUS_CLK)
> + cfg->f_min = MIN_BUS_CLK;
> +
>   cfg->f_max = host->src_clk_freq;
>  
>   cfg->b_max = 1024;
> 

[PATCH v2] mmc: mtk-sd: increase the minimum bus frequency

[Weijie Gao]

With a 48MHz input clock, the lowest bus frequency can be as low as
4800 / (4 * 4095) = 2930Hz. Such an extremely low frequency will cause
the mmc framework take seconds to finish the initialization.

Limiting the minimum bus frequency to a slightly higher value can solve the
issue without any side effects.

Signed-off-by: Weijie Gao 
---
 drivers/mmc/mtk-sd.c | 5 +
 1 file changed, 5 insertions(+)

diff --git a/drivers/mmc/mtk-sd.c b/drivers/mmc/mtk-sd.c
index 3b9c122..626a4d3 100644
--- a/drivers/mmc/mtk-sd.c
+++ b/drivers/mmc/mtk-sd.c
@@ -232,6 +232,8 @@
 
 #define SCLK_CYCLES_SHIFT  20
 
+#define MIN_BUS_CLK20
+
 #define CMD_INTS_MASK  \
(MSDC_INT_CMDRDY | MSDC_INT_RSPCRCERR | MSDC_INT_CMDTMO)
 
@@ -1639,6 +1641,9 @@ static int msdc_drv_probe(struct udevice *dev)
else
cfg->f_min = host->src_clk_freq / (4 * 4095);
 
+   if (cfg->f_min < MIN_BUS_CLK)
+   cfg->f_min = MIN_BUS_CLK;
+
cfg->f_max = host->src_clk_freq;
 
cfg->b_max = 1024;
-- 
1.9.1