linux-kernel - Re: [PATCH 3/3] mmc: sdhci-of-arasan: Add support for ZynqMP Platform Tap Delays Setup

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Message-ID: <5feac3fb-bef3-b7d1-57d6-81e115e1f555@xilinx.com>
Date:   Mon, 17 Jun 2019 13:27:43 +0200
From:   Michal Simek <michal.simek@...inx.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Manish Narani <manish.narani@...inx.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Michal Simek <michal.simek@...inx.com>,
        Adrian Hunter <adrian.hunter@...el.com>, rajan.vaja@...inx.com,
        jolly.shah@...inx.com, nava.manne@...inx.com,
        Olof Johansson <olof@...om.net>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 3/3] mmc: sdhci-of-arasan: Add support for ZynqMP Platform
 Tap Delays Setup

Hi,

On 17. 06. 19 13:15, Ulf Hansson wrote:
> On Tue, 11 Jun 2019 at 11:57, Manish Narani <manish.narani@...inx.com> wrote:
>>
>> Apart from taps set by auto tuning, ZynqMP platform has feature to set
>> the tap values manually. Add support to read tap delay values from
>> DT and set the same in HW via ZynqMP SoC framework. Reading Tap
>> Delays from DT is optional, if the property is not available in DT the
>> driver will use the pre-defined Tap Delay Values.
>>
>> Signed-off-by: Manish Narani <manish.narani@...inx.com>
>> ---
>>  drivers/mmc/host/sdhci-of-arasan.c | 173 ++++++++++++++++++++++++++++++++++++-
>>  1 file changed, 172 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/host/sdhci-of-arasan.c b/drivers/mmc/host/sdhci-of-arasan.c
>> index b12abf9..7af6cec 100644
>> --- a/drivers/mmc/host/sdhci-of-arasan.c
>> +++ b/drivers/mmc/host/sdhci-of-arasan.c
>> @@ -22,6 +22,7 @@
>>  #include <linux/phy/phy.h>
>>  #include <linux/regmap.h>
>>  #include <linux/of.h>
>> +#include <linux/firmware/xlnx-zynqmp.h>
>>
>>  #include "cqhci.h"
>>  #include "sdhci-pltfm.h"
>> @@ -32,6 +33,10 @@
>>
>>  #define PHY_CLK_TOO_SLOW_HZ            400000
>>
>> +/* Default settings for ZynqMP Tap Delays */
>> +#define ZYNQMP_ITAP_DELAYS {0, 0x15, 0x15, 0, 0x15, 0, 0, 0x3D, 0x12, 0, 0}
>> +#define ZYNQMP_OTAP_DELAYS {0, 0x5, 0x6, 0, 0x5, 0x3, 0x3, 0x4, 0x6, 0x3, 0}
>> +
>>  /*
>>   * On some SoCs the syscon area has a feature where the upper 16-bits of
>>   * each 32-bit register act as a write mask for the lower 16-bits.  This allows
>> @@ -81,6 +86,7 @@ struct sdhci_arasan_soc_ctl_map {
>>   * @sdcardclk:         Pointer to normal 'struct clock' for sdcardclk_hw.
>>   * @soc_ctl_base:      Pointer to regmap for syscon for soc_ctl registers.
>>   * @soc_ctl_map:       Map to get offsets into soc_ctl registers.
>> + * @of_data:           Platform specific runtime data storage pointer
>>   */
>>  struct sdhci_arasan_data {
>>         struct sdhci_host *host;
>> @@ -101,6 +107,15 @@ struct sdhci_arasan_data {
>>  /* Controller immediately reports SDHCI_CLOCK_INT_STABLE after enabling the
>>   * internal clock even when the clock isn't stable */
>>  #define SDHCI_ARASAN_QUIRK_CLOCK_UNSTABLE BIT(1)
>> +
>> +       void *of_data;
>> +};
>> +
>> +struct sdhci_arasan_zynqmp_data {
>> +       void (*set_tap_delay)(struct sdhci_host *host);
>> +       const struct zynqmp_eemi_ops *eemi_ops;
>> +       u8 tapdly[MMC_TIMING_MMC_HS400 + 1][2]; /* [0] for input delay, */
>> +                                               /* [1] for output delay */
>>  };
> 
> Please use two different structs, one for the clock provider data and
> one for the mmc variant/platform data. This makes the code more
> readable.

Origin version before sending that out was using two fields.
+	u32 itapdly[MMC_TIMING_MMC_HS400 + 1];
+	u32 otapdly[MMC_TIMING_MMC_HS400 + 1];

I did asked for putting it together to two dimensional array for
improving readability of this code. The reason was that you need to take
care about input/output together.
One thing I was also suggesting was to use instead of 2 just enum values
to specify IN=0/OUT/MAX to improve readability of this.
Do you think that using enum should be enough?


> In regards to the mmc data part, I suggest to drop the
> ->set_tap_delay() callback, but rather use a boolean flag to indicate
> whether clock phases needs to be changed for the variant. Potentially
> that could even be skipped and instead call clk_set_phase()
> unconditionally, as the clock core deals fine with clock providers
> that doesn't support the ->set_phase() callback.

In connection to another version of this driver for latest Xilinx chip
it would be better to keep set_tap_delay callback in the driver. The
reason is that new chip/ip is capable to setup tap delays directly
without asking firmware to do it. That's why for versal IP there is a
need to call different setup_tap_delay function.

> 
> [...]
> 
> Otherwise this looks good to me!
> 
> When it comes to patch1, I need an ack from Michal to pick it up.

I am waiting till Rob ack dt binding and then I wanted to talk to you if
you want to take it with 1/3 or if you want me to take all of them via
my tree.
In previous releases I was taking them via my tree because there were
several subsystem changing firmware interface. In this cycle there are
just small changes to firmware interface that's why taking it via your
tree shouldn't be a problem too.

Thanks,
Michal