linux-kernel - Re: [PATCH v3 2/5] i3c: mipi-i3c-hci: Add a quirk to set PIO mode

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Message-ID: <55b113d8-d782-4d6d-b5a9-e916a1a9b3b5@amd.com>
Date: Tue, 6 Aug 2024 13:36:18 +0530
From: Shyam Sundar S K <Shyam-sundar.S-k@....com>
To: Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Jarkko Nikula <jarkko.nikula@...ux.intel.com>
Cc: Guruvendra Punugupati <Guruvendra.Punugupati@....com>,
 Krishnamoorthi M <krishnamoorthi.m@....com>, linux-i3c@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/5] i3c: mipi-i3c-hci: Add a quirk to set PIO mode



On 8/6/2024 13:28, Shyam Sundar S K wrote:
> The AMD HCI controller currently only supports PIO mode but exposes DMA
> rings to the OS, which leads to the controller being configured in DMA
> mode. To address this, add a quirk to avoid configuring the controller in
> DMA mode and default to PIO mode.
> 
> Additionally, introduce a generic quirk infrastructure to the mipi-i3c-hci
> driver to facilitate seamless future quirk additions.
> 
> Co-developed-by: Krishnamoorthi M <krishnamoorthi.m@....com>
> Signed-off-by: Krishnamoorthi M <krishnamoorthi.m@....com>
> Co-developed-by: Guruvendra Punugupati <Guruvendra.Punugupati@....com>
> Signed-off-by: Guruvendra Punugupati <Guruvendra.Punugupati@....com>
> Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@....com>
> ---
>  drivers/i3c/master/mipi-i3c-hci/Makefile     |  3 ++-
>  drivers/i3c/master/mipi-i3c-hci/core.c       | 15 ++++++++++++++-
>  drivers/i3c/master/mipi-i3c-hci/hci.h        |  3 +++
>  drivers/i3c/master/mipi-i3c-hci/hci_quirks.c | 20 ++++++++++++++++++++
>  4 files changed, 39 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/i3c/master/mipi-i3c-hci/hci_quirks.c
> 
> diff --git a/drivers/i3c/master/mipi-i3c-hci/Makefile b/drivers/i3c/master/mipi-i3c-hci/Makefile
> index a658e7b8262c..1f8cd5c48fde 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/Makefile
> +++ b/drivers/i3c/master/mipi-i3c-hci/Makefile
> @@ -3,4 +3,5 @@
>  obj-$(CONFIG_MIPI_I3C_HCI)		+= mipi-i3c-hci.o
>  mipi-i3c-hci-y				:= core.o ext_caps.o pio.o dma.o \
>  					   cmd_v1.o cmd_v2.o \
> -					   dat_v1.o dct_v1.o
> +					   dat_v1.o dct_v1.o \
> +					   hci_quirks.o
> diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
> index 5ef848833a81..7843a3ac2121 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/core.c
> +++ b/drivers/i3c/master/mipi-i3c-hci/core.c
> @@ -33,6 +33,7 @@
>  #define reg_clear(r, v)		reg_write(r, reg_read(r) & ~(v))
>  
>  #define HCI_VERSION			0x00	/* HCI Version (in BCD) */
> +#define HCI_VERSION_V1			0x100	/* MIPI HCI Version number V1.0 */
>  
>  #define HC_CONTROL			0x04
>  #define HC_CONTROL_BUS_ENABLE		BIT(31)
> @@ -753,6 +754,14 @@ static int i3c_hci_init(struct i3c_hci *hci)
>  		return -EINVAL;
>  	}
>  
> +	/* Initialize quirks for AMD platforms */
> +	amd_i3c_hci_quirks_init(hci);
> +
> +	regval = reg_read(HCI_VERSION);
> +
> +	if (hci->quirks & HCI_QUIRK_PIO_MODE)
> +		hci->RHS_regs = NULL;
> +
>  	/* Try activating DMA operations first */
>  	if (hci->RHS_regs) {
>  		reg_clear(HC_CONTROL, HC_CONTROL_PIO_MODE);
> @@ -768,7 +777,11 @@ static int i3c_hci_init(struct i3c_hci *hci)
>  	/* If no DMA, try PIO */
>  	if (!hci->io && hci->PIO_regs) {
>  		reg_set(HC_CONTROL, HC_CONTROL_PIO_MODE);
> -		if (!(reg_read(HC_CONTROL) & HC_CONTROL_PIO_MODE)) {
> +		/*
> +		 * HC_CONTROL_PIO_MODE bit not present in HC_CONTROL register w.r.t V1.0
> +		 * specification. So skip checking PIO_MODE bit status
> +		 */
> +		if (regval > HCI_VERSION_V1 && !(reg_read(HC_CONTROL) & HC_CONTROL_PIO_MODE)) {

Jarkko, Apologies. I missed to address your comment on splitting the
version check and quirk stuff separately. Will do a resend, kindly
ignore this version.

Thanks,
Shyam


>  			dev_err(&hci->master.dev, "DMA mode is stuck\n");
>  			ret = -EIO;
>  		} else {
> diff --git a/drivers/i3c/master/mipi-i3c-hci/hci.h b/drivers/i3c/master/mipi-i3c-hci/hci.h
> index f94d95e024be..91e8a3833f3d 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/hci.h
> +++ b/drivers/i3c/master/mipi-i3c-hci/hci.h
> @@ -135,6 +135,7 @@ struct i3c_hci_dev_data {
>  
>  /* list of quirks */
>  #define HCI_QUIRK_RAW_CCC	BIT(1)	/* CCC framing must be explicit */
> +#define HCI_QUIRK_PIO_MODE	BIT(2)  /* Set PIO mode for AMD platforms */
>  
>  
>  /* global functions */
> @@ -142,4 +143,6 @@ void mipi_i3c_hci_resume(struct i3c_hci *hci);
>  void mipi_i3c_hci_pio_reset(struct i3c_hci *hci);
>  void mipi_i3c_hci_dct_index_reset(struct i3c_hci *hci);
>  
> +void amd_i3c_hci_quirks_init(struct i3c_hci *hci);
> +
>  #endif
> diff --git a/drivers/i3c/master/mipi-i3c-hci/hci_quirks.c b/drivers/i3c/master/mipi-i3c-hci/hci_quirks.c
> new file mode 100644
> index 000000000000..8a8fbd697175
> --- /dev/null
> +++ b/drivers/i3c/master/mipi-i3c-hci/hci_quirks.c
> @@ -0,0 +1,20 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * I3C HCI Quirks
> + *
> + * Copyright 2024 Advanced Micro Devices, Inc.
> + *
> + * Authors: Shyam Sundar S K <Shyam-sundar.S-k@....com>
> + *			Guruvendra Punugupati <Guruvendra.Punugupati@....com>
> + */
> +
> +#include <linux/i3c/master.h>
> +#include "hci.h"
> +
> +void amd_i3c_hci_quirks_init(struct i3c_hci *hci)
> +{
> +#if defined(CONFIG_X86)
> +	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
> +		hci->quirks |= HCI_QUIRK_PIO_MODE;
> +#endif
> +}