[PATCH] mmc: meson: initial ocr available by default value

[PATCH] mmc: meson: initial ocr available by default value

[Rong Chen]

The patch will add a value of ocr supported by the controller,
to specify some of voltage values are supported.

Ocr_avail should place an initial value to avoid uncertain
value for the platform that unsupport regulator such as S4.

Signed-off-by: Rong Chen <rong.chen@amlogic.com>
---
 drivers/mmc/host/meson-gx-mmc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index 8f36536cb1b6..c339e12d5516 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -4,6 +4,9 @@
  *
  * Copyright (c) 2016 BayLibre, SAS.
  * Author: Kevin Hilman <khilman@baylibre.com>
+ *
+ * Copyright (c) 2021 Amlogic, inc.
+ * Author: Rong Chen <Rong.Chen@amlogic.com>
  */
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -130,6 +133,7 @@
 #define SD_EMMC_DESC_CHAIN_MODE BIT(1)
 
 #define MUX_CLK_NUM_PARENTS 2
+#define SD_EMMC_OCR_AVAIL 0x200080
 
 struct meson_mmc_data {
 	unsigned int tx_delay_mask;
@@ -1150,6 +1154,7 @@ static int meson_mmc_probe(struct platform_device *pdev)
 	host->dram_access_quirk = device_property_read_bool(&pdev->dev,
 					"amlogic,dram-access-quirk");
 
+	mmc->ocr_avail = SD_EMMC_OCR_AVAIL;
 	/* Get regulators and the supported OCR mask */
 	host->vqmmc_enabled = false;
 	ret = mmc_regulator_get_supply(mmc);

base-commit: 141edd9e99eb91393e8a4d97742bd98328bff724
-- 
2.25.1

Re: [PATCH] mmc: meson: initial ocr available by default value

[Martin Blumenstingl]

Hello,

On Mon, Dec 13, 2021 at 8:03 AM Rong Chen <rong.chen@amlogic.com> wrote:
>
> The patch will add a value of ocr supported by the controller,
> to specify some of voltage values are supported.
Can you please share some details on this topic?

We already have many boards upstreamed which work fine without
manually setting ocr_avail in the driver.
In general there's two types of boards:
1) boards where the regulator can switch between different voltages.
One example is the Odroid-C2, see meson-gxbb-odroidc2.dts [0]
Here we specify:
  vmmc-supply = <&tflash_vdd>;
  vqmmc-supply = <&tf_io>;
&tflash_vdd is either turned off or at 3.3V when turned on.
&tf_io can be either turned off, 1.8V or 3.3V.

2) boards where the voltages are fixed.
One example is Radxa Zero, see meson-g12a-radxa-zero.dts [1]
For the SD card the board uses:
  vmmc-supply = <&vddao_3v3>;
  vqmmc-supply = <&vddao_3v3>;
(meaning fixed 3.3V always-on power source for both VMMC and VQMMC)
and for eMMC the board uses:
  vmmc-supply = <&vcc_3v3>;
  vqmmc-supply = <&vcc_1v8>;
(meaning: 3.3V always-on power source for vmmc and 1.8V always-on
power source for VQMMC)

With the information from the regulators the MMC core will
automatically detect ocr_avail in Linux.
Or in other words: your .dts may be missing the link between regulator
and MMC controller vmmc/vqmmc.
Can you please double-check this?


Best regards,
Martin


[0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts?id=2585cf9dfaaddf00b069673f27bb3f8530e2039c#n354
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/amlogic/meson-g12a-radxa-zero.dts?id=2585cf9dfaaddf00b069673f27bb3f8530e2039c#n333

Re: [PATCH] mmc: meson: initial ocr available by default value

[Jerome Brunet]

On Mon 13 Dec 2021 at 19:50, "rong.chen@amlogic.com" <rong.chen@amlogic.com> wrote:

> Hello,
> If 3.3V always-on power source for vmmc is supplied by hardware boards fixed, don't need regulator in software, so  .dts unnecessary the link between regulator
> and MMC controller vmmc/vqmmc. 

Controllable or not, your vmmc/vqmmc regulators should be described in
DT.

There are several examples of this in arch/arm64/boot/dts/amlogic/*.dts


>
> ------------------------------------------------------------------------------------------------------------------------------------------------------
> rong.chen@amlogic.com
>
>   
>  From: Martin Blumenstingl
>  Date: 2021-12-13 16:00
>  To: Rong Chen
>  CC: Ulf Hansson; Neil Armstrong; Kevin Hilman; Jerome Brunet; --to=1131046452; 45581586; linux-mmc; linux-arm-kernel; linux-amlogic; linux-kernel
>  Subject: Re: [PATCH] mmc: meson: initial ocr available by default value
>  [ EXTERNAL EMAIL ]
>   
>  Hello,
>   
>  On Mon, Dec 13, 2021 at 8:03 AM Rong Chen <rong.chen@amlogic.com> wrote:
>  >
>  > The patch will add a value of ocr supported by the controller,
>  > to specify some of voltage values are supported.
>  Can you please share some details on this topic?
>   
>  We already have many boards upstreamed which work fine without
>  manually setting ocr_avail in the driver.
>  In general there's two types of boards:
>  1) boards where the regulator can switch between different voltages.
>  One example is the Odroid-C2, see meson-gxbb-odroidc2.dts [0]
>  Here we specify:
>    vmmc-supply = <&tflash_vdd>;
>    vqmmc-supply = <&tf_io>;
>  &tflash_vdd is either turned off or at 3.3V when turned on.
>  &tf_io can be either turned off, 1.8V or 3.3V.
>   
>  2) boards where the voltages are fixed.
>  One example is Radxa Zero, see meson-g12a-radxa-zero.dts [1]
>  For the SD card the board uses:
>    vmmc-supply = <&vddao_3v3>;
>    vqmmc-supply = <&vddao_3v3>;
>  (meaning fixed 3.3V always-on power source for both VMMC and VQMMC)
>  and for eMMC the board uses:
>    vmmc-supply = <&vcc_3v3>;
>    vqmmc-supply = <&vcc_1v8>;
>  (meaning: 3.3V always-on power source for vmmc and 1.8V always-on
>  power source for VQMMC)
>   
>  With the information from the regulators the MMC core will
>  automatically detect ocr_avail in Linux.
>  Or in other words: your .dts may be missing the link between regulator
>  and MMC controller vmmc/vqmmc.
>  Can you please double-check this?
>   
>   
>  Best regards,
>  Martin
>   
>   
>  [0]
>  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts?id=2585cf9dfaaddf00b069673f27bb3f8530e2039c#n354
>  
>  [1]
>  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/amlogic/meson-g12a-radxa-zero.dts?id=2585cf9dfaaddf00b069673f27bb3f8530e2039c#n333

Re: [PATCH] mmc: meson: initial ocr available by default value

[Martin Blumenstingl]

On Mon, Dec 13, 2021 at 2:25 PM Jerome Brunet <jbrunet@baylibre.com> wrote:
>
>
> On Mon 13 Dec 2021 at 19:50, "rong.chen@amlogic.com" <rong.chen@amlogic.com> wrote:
>
> > Hello,
> > If 3.3V always-on power source for vmmc is supplied by hardware boards fixed, don't need regulator in software, so  .dts unnecessary the link between regulator
> > and MMC controller vmmc/vqmmc.
>
> Controllable or not, your vmmc/vqmmc regulators should be described in
> DT.
I agree with Jerome. Here are the two reasons why I think that it's
best to describe these regulators in device-tree:
- device-tree is there to describe the hardware. It's especially
useful for non-discoverable information (USB and PCI IDs are
discoverable examples), for example: voltage supply of an MMC
controller, UART IRQ line, ...
- reviewing board.dts would be a lot harder if we rely on defaults
(defaults which cannot be described in a device-tree schema). For
meson-g12a-radxa-zero.dts this means we could omit the vmmc/vqmmc
regulators for the SD card slot but we need them for the eMMC (because
vqmmc is fixed at 1.8V).


Best regards,
Martin