Messages in this thread | | | Subject | Re: [PATCH V15 3/6] i2c: tegra: fix maximum transfer size | From | Dmitry Osipenko <> | Date | Fri, 8 Feb 2019 01:09:47 +0300 |
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08.02.2019 0:47, Sowjanya Komatineni пишет: > Tegra194 supports maximum 64K bytes transfer per packet. > Tegra186 and prior supports maximum 4K bytes transfer per packet. > This includes 12 bytes of packet header. > > This patch fixes max write length to account for packet header size > for transfers.
The commit message isn't accurate. We are not actually fixing anything here, this patch is just a preparation for adding DMA support that require the packet-header size to be excluded from the overall TX size-quirk because the packet-header is the part of the DMA transfer.
Given how small this change is, it's probably not really worth to factor out it into a separate patch, let's just squash it to to the DMA-patch.
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com> > --- > [V15] : This is new patch in this series. > > drivers/i2c/busses/i2c-tegra.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c > index 3758c7a2c781..ab474cc86e0a 100644 > --- a/drivers/i2c/busses/i2c-tegra.c > +++ b/drivers/i2c/busses/i2c-tegra.c > @@ -125,6 +125,9 @@ > #define I2C_MST_FIFO_STATUS_TX_MASK 0xff0000 > #define I2C_MST_FIFO_STATUS_TX_SHIFT 16 > > +/* Packet header size in bytes */ > +#define I2C_PACKET_HEADER_SIZE 12 > + > /* > * msg_end_type: The bus control which need to be send at end of transfer. > * @MSG_END_STOP: Send stop pulse at end of transfer. > @@ -900,11 +903,13 @@ static const struct i2c_algorithm tegra_i2c_algo = { > static const struct i2c_adapter_quirks tegra_i2c_quirks = { > .flags = I2C_AQ_NO_ZERO_LEN, > .max_read_len = 4096, > - .max_write_len = 4096, > + .max_write_len = 4096 - I2C_PACKET_HEADER_SIZE, > }; > > static const struct i2c_adapter_quirks tegra194_i2c_quirks = { > .flags = I2C_AQ_NO_ZERO_LEN, > + .max_read_len = 65535, > + .max_write_len = 65535 - I2C_PACKET_HEADER_SIZE, > };
This is wrong, 65535 = 64 * 1024 - 1.
Let's just use size-constants provided by kernel:
static const struct i2c_adapter_quirks tegra_i2c_quirks = { .flags = I2C_AQ_NO_ZERO_LEN, .max_read_len = SZ_4K, .max_write_len = SZ_4K - I2C_PACKET_HEADER_SIZE, };
static const struct i2c_adapter_quirks tegra194_i2c_quirks = { .flags = I2C_AQ_NO_ZERO_LEN, .max_read_len = SZ_64K, .max_write_len = SZ_64K - I2C_PACKET_HEADER_SIZE, };
I'll take a look at other patches later today, no need to send out new version right now.
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