Re: [PATCH v2 2/5] i3c: mipi-i3c-hci: Add a quirk to set PIO mode

Jarkko Nikula
2024-08-02T13:58:42Z

Hi

On 7/24/24 10:12 AM, 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@amd.com>
> Signed-off-by: Krishnamoorthi M <krishnamoorthi.m@amd.com>
> Co-developed-by: Guruvendra Punugupati <Guruvendra.Punugupati@amd.com>
> Signed-off-by: Guruvendra Punugupati <Guruvendra.Punugupati@amd.com>
> Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.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 +++
> 3 files changed, 19 insertions(+), 2 deletions(-)
>
> 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

This doesn't build since hci_quirks.c is added by the patch 4/5. One
idea below.

> diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
> index dbc8c38bd962..8bb422ab1d01 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)
> @@ -745,6 +746,14 @@ 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_AMD_PIO_MODE)
> + hci->RHS_regs = NULL;
> +
> /* Try activating DMA operations first */
> if (hci->RHS_regs) {
> reg_clear(HC_CONTROL, HC_CONTROL_PIO_MODE);
> @@ -760,7 +769,11 @@ 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)) {
> dev_err(&hci->master.dev, "DMA mode is stuck\n");
> ret = -EIO;
> } else {

This is true, I see this now from pre-v1.0, v1.0. v1.1 and v1.2 specs
too, HC_CONTROL_PIO_MODE bit is present only after v1.0. And therefore
version != HCI_VERSION_V1 check is not fully correct since bit is not
present in pre-v1.0 HW versions either.

I'd split this patch and do version check alone here (perhaps as a first
patch) and do quirk stuff later where hci_quirks.c is added.